For many years I'd been mulling over in the back of my mind
various ways that optical ("lightbeam") communications could be
long distances. Years ago, I'd observed that even a modest,
2 AA-cell focused-beam flashlight could be easily seen over a distance
of more than 30 miles (50km) and that sighting even the lowest-power
similar distances was fairly trivial - even if holding a steady beam
. Other than keeping such ideas in the back of my
really did more that this - at least until the summer of 2006, when I
a web site that intrigued me, the "Modulated
Light DX page
written by Chris Long and Mike Groth. While I'd been following
the history and progress of such things all along, this and similar
pages rekindled the intrigue, causing me to do additional research and
began to build things.
Working up to the distance...
Over the winter of 2006-2007 I spent some time building, refining, and
rebuilding various circuits having to do with optical
communications. Of particular interest to me were circuits used
detecting weak optical signals and it was those that I
wanted to see if I could improve. After considerable
experimentation, head-scratching, cogitation, and testing, I was
finally able to
come up with a fairly simple optical
that was at least
than other voice-bandwidth circuits that were out
there. Other experimentation was done on modulating light
sources and the first serious attempt at this was building a PIC-based PWM
(Pulse-Width Modulation) circuit
by a simpler current-linear
- both being approaches that
seemed to work extremely well.
After this came the hard part: Actually assembling the mechanical
assemblies that made up the optical transceivers. I decided to
follow the field-proven
of using large, plastic,
in conjunction with high-power LEDs for the
source of light emissions with a second parallel lens and a photodiode
for reception and the stated reasons for taking this approach
seemed to me to be quite well thought-out and sound - both
technically and practically. This led to the eventual
construction of an optical
that consisted of a pair of
identical Fresnel lenses, each being 318 x 250mm (12.5" x 9.8")
mounted side-by-side in a rigid, wooden enclosure comprising an optical
transceiver with parallel transmit and
receive "beams." In taking this approach, proper aiming of either
the transmitter or
would guarantee that the other was already
aimed - or very close to being properly aimed - requiring only a single
gear to be deployed with precision.
After completing this first transceiver, hastily I built a second
to be used at the "other" end of test path.
Constructed of foam-core
posterboard, picture frames and inexpensive, flexible vinyl "full-page"
lenses, this transceiver used, for the optical emitter and transmitter
assemblies, my original, roughly-repackaged prototype circuits.
While it was
neither pretty or
capable of particularly high performance, it
filled the need of being the "other" unit with which communications
carried out for testing: After all, what good would a receiver be
if there were no transmitters?
we completed our first 2-way optical QSO
with a path that crossed the Salt Lake Valley, a distance of about 24
km (15 miles.) We were pleased to note that our signals were
extremely strong and, despite the fact that our optical path crossed
directly over downtown Salt Lake City, they seemed to have
30-40dB signal-noise ratio - if you ignored some 120 Hz hum and the
occasional "buzz" from an unseen, failing streetlight. We also
fair amount of amplitude scintillation, but this wasn't too
considering that the streetlights visible from our locations also
seemed to shimmer being subject to the turbulence caused by the
temperature inversion layer in the valley.
Bolstered by this success we conducted several other experiments over
the next several months, continuing to improve and build more gear,
gain experience, and refine our techniques. Finally, for August
18, 2007, we decided on a more ambitious goal: The
spanning of a
107-mile optical path
. By this time, I'd completed a third
using a pair of larger (430mm x 404mm, or 16.9"
Fresnel lenses, and it significantly out-performed the
version that had been used earlier. On this occasion we were
dismayed by the amount of haze in the air - the remnants of smoke that
had blown into the area just that day from California wildfires.
Ron, K7RJ and company (his wife Elaine, N7BDZ and Gordon, K7HFV) who
the northern end of the path (near Willard Peak, north of Ogden, Utah)
experienced even more trials, having had to retreat on three occasions
from their chosen vantage point due to brief, but intense
thunderstorms. Finally, just before midnight, a voice exchange
was completed with some difficulty - despite the fact that they never
could see the distant transmitter with the naked eye due to the
haze and light pollution - over this path, with the southern end (with
Clint, KA7OEI and Tom, W7ETR) located near Mount Nebo, southeast of
Finding a longer path:
Following the successful 107-mile exchange we decided that it was
time to try an even-greater distance. After staring at maps and
over topographical data we found what we believed to be a 173-mile
line-of-sight shot that seemed to provide reasonable accessibility at
both ends. This path spanned the Great Salt Lake
Desert - some of the flattest, desolate, and most remote land in the
continental U.S. At the south end of this path was Swasey Peak,
tallest point in the House range, a series of mountains about 70 miles
west of Delta, in west-central Utah. Because Gordon had hiked
peak on more than one occasion we were confident that this goal was
At the north end of the path was George Peak in the Raft River range,
an obscure line of mountains that run east and west in the extreme
northwest corner of Utah,
just south of the Idaho boarder. None of us had ever been there
before, but our research indicated that it should be possible to drive
there using a high-clearance 4-wheel drive vehicle so, on August 25,
2007, Ron and Gordon piled into my Jeep (along with a 2nd
swiped from Ron's Jeep as
recommended by more than one account) and we headed north to
Following the Interstate highway nearly to the Idaho border, we turned
west onto a state highway, following it as the road swung north into
passing the Raft River range, and we then turned off onto a gravel road
. In this small town (a spread-out collection of
really) we turned onto a county road that began to take us up canyons
on the northern slope of the range. As we continued to climb, the
became rougher and we resorted to peering at maps and using our
intuition to guide us onto the
one road that would take us to the top of the mountain range.
Top: A computer
simulated view (top half) and contrast-enhanced view (bottom half) from
25, 2007 showing the effects of refraction.
Bottom: An overlaid map and photo showing the 173-mile
Click on either image for a larger version.
Luckily, our guesses were correct and we soon found ourselves at the
of the ridge. Traveling for a short distance, we ran into a
problem: The road stopped at a fence gate that
plastered with "No Trespassing" signs. At this point, we simply
to follow what looked like road that paralleled the fence only
to discover, after traveling several hundred feet - and past a point at
which we could safely turn around - that this "road" had degenerated
a rather precarious dirt path traversing a steep slope. After
several hundred more feet, fighting all the while to keep the Jeep on
the road and moving in a generally forward direction, the path leveled
out once again and
rejoined what appeared to be the main road. After a combination
both swearing at and praising deities we vowed that we would never
travel on that "road" again and simply stay on what had appeared to
have been the main road,
regardless of what the signs on the gates said!
Looking for Swasey Peak:
Having passed these trials, we drove along the range's ridge top,
looking to the south. On this day, the air was quite hazy -
due to wildfires that were burning in California, and in the
could vaguely spot, with our naked eyes, the outline of a mountain
range that we thought
to be the House range: In comparing
outline and position with a computer-simulated view, it "looked" to be
a fairly close match as best as we could guess.
Upon seeing this distant mountain we stopped to get a better look, but
when we looked through binoculars or a telescope the distant outline
disappear - only to reappear once again when viewed with the naked
eye. We finally realized what was happening: Our
eyes and brain are "wired" to look at objects, in part, by detecting
but in this case the haze reduced the contrast considerably. With
the naked eye, the distant mountain was quite small but with the
enlarged image in the binoculars and telescope the apparent contrast
the object's outline was greatly
diminished. The trick to being able to visualize the distant
mountain turned out be keeping the
as our eyes and brain are much
to slight changes in brightness of moving
objects than stationary
ones. After discovering this fact, we noticed with some amusement
that the distant mountain seemed to vanish from sight once we stopped
wiggling the binoculars only to magically reappear when we moved them
again. For later analysis we also took
at this same location and noted the GPS coordinates.
Continuing onwards, we drove along the ridge toward George Peak.
we got near the GPS coordinates that I had marked for the peak we
were somewhat disappointed - but not surprised: The highest spot
in the neighborhood, the peak, was one of several gentle, nondescript
rose above the
road only by a few 10's of feet. Stopping, we ate lunch, looked
through binoculars and telescopes, took pictures, recorded GPS
coordinates, and thought apprehensively about the
return trip along the road.
Retracing our path - but not
taking the "road" that had
paralleled the fence line - we soon came to the gate that marked the
boundary of the private land. While many of the markings were the
same at this gate, we noticed another sign - one that had been missing
other end of the road - indicating that this was,
public right-of-way plus the admonition that those traveling
stay on the road. This sign seemed to
register with what we thought
we'd remembered about Utah laws
governing the use of such roads and our initial interpretation of the
county parcel maps: Always leave a gate the way you
found it, and don't go off the road! With relief, we crossed this
parcel with no difficulty and soon found ourselves at the other gate
and in familiar territory.
Retracing our steps down the mountain we found ourselves hurtling
along the state highway a bit more than an hour later - until I heard
the unwelcome sound of a noisy tire. Quickly pulling over I
discovered that a large rock that had embedded itself in
the middle of the
tread of a rear tire. After 45 minutes of changing the tire and
spare up to full pressure, we were again underway - but with only one
Analyzing the path:
Upon returning home I was able to analyze the photographs that I had
taken. Fortunately, my digital SLR camera takes pictures in "Raw"
mode, preserving the digital picture without loss caused by converting
it to a lossy format like JPEG. Through considerable contrast
enhancement, the "stacking" of several similar images using an
astronomical photo processing program and making a comparison against
computer-generated view I
discovered that the faint outline that we'd seen
Swasey Peak but was, in fact, a range that was
about 25 miles (40km) closer - the Fish Springs mountains - a mere
150 or so
miles (240km) away. Unnoticed (or invisible) at the time of our
mountaintop visit was another
small bump in the distance that was, in fact, Swasey Peak.
Interestingly, the first set of pictures were taken at a location that,
according to the computer analysis, was barely
with Swasey Peak. At the time of the site visit we had assumed
that the just-visible mountain that we'd seen in the distance was
Swasey Peak and that there was some sort of parallax error in the
computer simulation, but analysis revealed that not only was the
computer simulation correct in its positioning of the distant features,
but also that the apparent height of Swasey Peak above the horizon was
being enhanced by atmospheric refraction - a property that the program
did not take into account: Figure 1
shows a comparison
between the computer simulation and an actual photograph taken from
this same location.
Building confidence - A retry of the 107-mile path:
Having verified to our satisfaction that we could not only get to the
top of the Raft River mountains but also that we also had a
Swasey Peak, we began to plan for our next adventure. Over the
next several weeks we watched the weather and the air - but before we
did this, we wanted to try our 107-mile path again in clearer weather
to make sure that our gear was working, to gain more experience with
its setup and operation, and to see how well it would work over a long
optical path given reasonably good seeing conditions: If we had
success over a 107-mile path we
felt confident that we should be able to manage a 173-mile path.
A few weeks later, on September
, we got our chance: Taking
advantage of clear weather just after a storm front had moved through
we went back to our respective locations - Ron, Gordon and Elaine at
Inspiration Point while I went (with Dale, WB7FID) back to the location
near Mt. Nebo. This time, signal-to-noise
ratios were 26dB better than before and voice was "armchair"
copy. Over the several hours of experimentation we were able to
transmit not only voice, but SSTV
(Slow-Scan Television) images over the LED link - even
switching over to using a "raw" Laser Pointer for one experiment and a
Laser module collimated by an 8" reflector telescope in another.
With our success on the clear-weather 107-mile path we waited for our
window to attempt the 173-mile path between Swasey and George
Peak but in the following weeks we were dismayed by the appearance
of bad weather and/or frequent haze - some of the latter resulting from
still-burning wildfires around the western U.S.
The 173-mile path - A first attempt:
In the days before the trip:
Top Left: A view toward
Swasey Peak from 10-15 miles away. The outline of the mountains
can just be seen to the left of the road, in the haze - look at this enhanced image if you
don't believe me!
Top Right: "Team Swasey" with the peak in the
background. L->R: Brett, N7KG; Tom, W7ETR;
Ron, K7RJ; Gordon, K7HFV
Bottom Left: Brett, struggling up the
scree-covered slope. Note the "Muck" in the air in the background.
Bottom Center: Ron, with optical transceiver strapped to
his backpack. Note again, the amount of haze in the background.
Click on either image for a larger version.
In preparation for this trip we knew that it likely that we would be
able to communicate with each other via 2 meter simplex, but because
of the distance we expected that signals would be weak. We had
also arranged to meet with Chris, VK3AML on an IRLP
node on a linked
UHF repeater system operated by Dave, WA7GIE. To assure that we
would be able to talk to each other directly via simplex as well as get
UHF repeater system, each of us planned to take along both VHF and UHF
portable beams. (It should be noted that cell telephone
service at each site was spotty at best and due to the phones' running
at full power and trying to communicate with the cell sites, battery
life was only a few hours - even if the phones were simply left on and
After a week that had started out with bad weather we could see from
the forecast that the upcoming weekend, Saturday the 15th
was likely to be clear, albeit windy, so we chose that date for our
attempt. In preparation, Gordon went over to Ron's house on the
prior Tuesday to repair his 2 meter "Walking Stick" beam - a portable
antenna that he'd built years before, but had not gotten around to
putting back into operational condition after several key pieces had
gotten broken or lost. By the end of the evening the 2 meter
beam was once again whole, but they had only started on construction of
a 70cm version and were missing a few key raw materials. In the
following days Gordon managed to obtain the remaining materials and
mostly complete the antenna, but he had yet to do the final tuning.
Departure - September 15, 2007:
As Murphy dictated it wasn't until the morning of the scheduled
departure that Gordon was able to get back with Ron to tune the antenna
task that seemed to prove futile until it was realized that, for
whatever reason, the VSWR bridge being used refused to read lower than
on a known-good dummy load! Having already wasted most of an
"guesstimate" was made on what seemed to be the best match, the final
items were thrown into the vehicles, and Ron took off with Gordon and
Brett N7KG under separate cover. At about 25 minutes into the
trip I turned on the radio to hear Ron mention that he'd realized that
he'd forgotten the digital audio recorder that was to record the output
of the optical receiver. While the first inclination was to
simply forget it, I volunteered to deliver to him one of mine, meeting
him halfway, but then his wife, Elaine, N7BDZ appeared on the air and
offer: This latter offer was accepted, so Brett and Gordon turned
while Ron continued on to Orem to pick up Tom. After another 30
minutes or so a meeting occurred and Brett and Gordon were again
underway with the recorder in-hand and Ron and Tom considerably
ahead. At this point the
south-going group was now two
hours behind the original
schedule with Ron and Tom 30 minutes ahead of Brett - but at least
everyone in "Team Swasey" was headed in the right direction!
After loading my Jeep I headed over to Ron's house
to pick up Elaine who was accompanying me to George Peak. By this
time I'd replaced all of the tires and acquired a second
spare of my own so, after throwing Elaine's gear into the car, we
headed north. Meanwhile, Ron had stopped along US Highway 6 and
waited for Brett and Gordon to catch up: Before too long,
the two groups were reunited and heading toward Delta.
"We continued uneventfully, arriving in Delta a bit before 4
was somewhat too late for lunch and a bit early for dinner, but
something we could eat on our way to the trailhead sounded like a
time-saver. We could call it 'linner.' The only fast-food option seemed
to be McDonald's, so we chose our combo numbers with care.
"I had noted instructions to reach the trailhead from the Dave Hall
Hiker's Guide to Utah. Those
instructions, however, turned out to be almost useless as roads and
signage had changed over the years. We were supposed to look for a
turnoff 12 miles from Delta, but found none. Thanks to Ron's map
book... we turned onto a major gravel road at about 27 miles. This road
was signed for the "U-Dig" trilobite beds. This was clearly a different
approach than [the one that] John Parken and I had taken decades back,
as the older approach had followed the IPP DC power line
for the first part of its route.
"The route-finding rules seemed simple:
1. Stay on major gravel roads.
2. Take the choice that goes up.
3. If #2 isn't clear, go straight.
"As we looked for the turnoff, we began to sense a problem.
to our GPS receivers, the distance between us and our destination
mountain was narrowing, but we still could not see it. In fact we could
see hardly anything to the west. The vista faded into a gray haze of
dust, sand, and smoke in some combination. This was not
situation for a long-distance optical experiment!"
It seemed that high winds
near the ground on that day - and the day before - had whipped quite a
bit of dirt into the air, a fact unknown to us beforehand. At
about this time I received a call on my cell phone from Brett as I
passed through Ogden. Amongst the broken syllables and
disconnected phrases caused by the poor phone coverage in the desert
Delta I was able to make out that seeing conditions were not at all
good, but because we were already committed to the task, we
decided to carry on, despite the unfavorable omens. At about
point Elaine and I started getting better views toward the west and
noticed that while we could see mountains that were 60-70 miles
distant, there seemed to be more haze in the air than we would have
liked to see.
Before too long, Elaine and I were joined by Paul, W7PAH along with his
son and grandson in their vehicle and we found ourselves traveling west
along Utah Highway 30, now in sight of the Raft River range as well as
the Goose Creek mountains that sit in Utah along the Nevada
border. Being able to see over this distance, the density of the
haze was increasingly apparent as a pall of dust. Because we were
nearly there - and out of communications with the other group for the
time being - we continued toward our destination.
"Team Swasey" begins its trek:
"We began to make out a hazy outline of a mountain when
the magic of GPS told us we were within three miles of our
The mountain turned out to be, in fact, Swasey Peak. As it
base of the mountain, our road made a turn to the west and soon reached
a four-way junction. After consulting with some hunters camped
junction, we determined that a right turn would take us to our
"The road ended in what might have
been called a 'campground,' although there were no signs or facilities.
The road split into a small grid of orthogonal roads ending at a sharp
drop-off to the desert floor below [and the] GPS gave our elevation as
feet. We were essentially at the trailhead. Ron and Tom found a short
road or track that got us a few hundred yards closer to the mountain,
so we drove to the end of it and declared it to be our trailhead.
"We prepared our packs for the hike up the mountain, dividing up the
equipment and batteries necessary for the light communication. Ron had
devised a way to carry the box with the optics and had built a small
table that could be assembled on site and used to support the box on
"Brett decided his heavy tripod had enough more utility than my light
one that he opted to carry his. Therefore we used mine to take the
'obligatory group picture' of the party with packs on. After that, the
tripod was relegated to supporting a 'glow stick' that we
hoped would guide us back to the vehicles after dark. Ron had thought
to purchase several 'glow sticks,' chemical lights that, once
activated, would send out light for most of the night. Using these to
mark our trail seemed like a great idea."
"Team George" arrives onsite:
Top: Ron and Tom
setting up the gear at the chosen
site. In the background is a view toward the north, showing the
severity of the haze in the air. In the background haze can just
be seen the Fish Creek mountains, about 20-25 miles distant.
Center: Ron, setting up the optical transceiver.
Bottom: Sunset, as seen from Swasey Peak.
Click on an image for a larger version.
Just after crossing into Idaho, I headed west along a gravel road
toward Standrod and then toward the south, up the increasingly-steep
canyon road. After an hour or so of driving, we found ourselves
in familiar territory on the ridge top of the Raft River
mountains. As it turns out, there's no particular reason to set
up at George Peak itself, as the mid-path blockage - the Newfoundland
Mountains - a crescent-shaped range about 50 miles to the south - is
cleared by traversing the ridgetop road to a point less than halfway
between the point where the access road joins the ridge and the peak
itself. Because of this, we stopped at a convenient wide spot on
road. Our now-commanding view revealed the
extent of the haze: We could just make out features
that were about 70-90 miles distant, but beyond this there seemed to be
veil of dust: Despite a degree of disappointment, we set up
our gear, anyway, and waited to hear from the other end.
"What a royal pine in the..."
Waiting for dark:
"Pack preparation took a little less
than a half-hour and we started hiking at about 4:55. Instead of
following a clear, easy trail, we found ourselves hunting for a route
through thick growth of pinion and mountain mahogany.
tens of yards and find our trail blocked
by branches, then back up and try another possible path. The branches
seemed particularly prone to grabbing antenna parts on the backs of
packs, making the bearer try to figure out what was hanging him up in
an area he could not see as he tried miscellaneous gyrations to try to
get free. Progress (and frequently, retrogress) was slow.
"The route took us onto the summit ridge and we thought that once we
attained the ridge, our troubles would be over. This was only partly
true. Once we were near the ridge, the mountain mahogany became much
less pervasive and there were longer clear stretches we could hike
through. But as we progressed higher we encountered very steep slopes
littered with loose gravel or loose soil and pine needles. As 7 P.M.
approached, Ron and Tom, who were in the lead, picked a location for
our anticipated light QSO. It was a rock outcropping that was right on
the ridge, was clear of trees, and had an unobstructed view to the
north. We were still about 400 vertical feet shy of the summit, but
with sunset approaching it didn't appear we could reach the summit
safely before dark.
"The ascent to the ridge was the hardest part of the hike for me. I saw
what seemed to be a clear trail ascending and wondered why Brett had
not taken it. But I gave it a try and found myself slipping down the
scree faster than I could ascend. I gingerly picked my way over to
Brett's route and had better luck.
"When Brett and I arrived at the site, Ron and Tom had already begun
unpacking and setting up the optical transceiver. Ron's low table
worked wonderfully and gave us a stable base for the large box with the
optics. We had been worried about our ability to communicate with the
other end. It turned out that Ron, on arrival, had given Clint a call
on 147.54 simplex using just his handheld and a rubber duck. Clint came
back almost immediately. Is a 173-mile simplex QSO on a rubber
worth any points in the contest?"
Upon making contact with Team Swasey, Brett and Gordon
proceeded to set
up their portable Yagi, improving their signal to us noticeably as
compared to the rubber duck. For our end I had brought along a
as it was extremely portable in that its
elements could be folded together but very soon after setting up, we
problem: Its flat elements seemed to catch the slightest puff of
and would fold back, disturbing the elements' orientation and wrecking
the antenna's directivity. Elaine disappeared over the ridge to
north in the direction of some Lodgepole pine
trees and returned with some sticks that I taped to the upper half of
the elements - a strategy that
the problem (see Figure 4.)
As there was still at least an hour before it would be dark enough to
attempt any optical communications, we cooked and ate our dinner - a
freeze-dried epicurean delight. We also took this time to
to Paul W7PAH, his son Scott KE7OMB and Scott's son, Brady, how the
transceiver worked. In the meantime, Team Swasey decided to
what other repeaters they could hit on 2 meters and were surprised to
discover that they were able to get into the 146.76 repeater on Lake
Mountain, over 90 miles away and behind several mountain ranges.
they were able to bring up an IRLP node through the repeater, they were
surprised to discover that they'd not
connected to the intended
somewhat dismayed when, despite numerous attempts,
they were unable to successfully disconnect: Eventually they
allowing the node to time itself out.
As the sun sank lower in the west a line of demarcation appeared
across the its disk with the upper half being fairly clear but the
lower half being much dimmer and redder, obscured by the airborne
dust - an indicator of the true magnitude of the haze - see Figure
. With the
gathering darkness the temperature also dropped into the
high 30's at the top of the Raft River range but the slight breeze
that had been blowing
when we arrived had all but ceased and the lower half of the Yagi's
elements were gently oscillating
due to the airfoil created by the curvature of their tape-measure
Photons with Phutility:
After the gloaming, we began our attempts to signal each other.
Top Left: The site selected
north end of the path. The actual optical path is to the right of
the distant mounts that can be see to the right of the tripod.
Top Right: Elaine found some sticks that were taped to
the elements of the tape-measure Yagi to prevent them from deflecting
in the wind.
Bottom Left: Setting up the optical transceiver on the
Raft River range. L->R: Clint, Brady and his dad, Scott,
Bottom Right: Sunset, as seen from the north end of the
path near George Peak. All but the top portion of the sun's disk
is below the
layer of haze present in the atmosphere on that day.
Click on an image for a larger version.
Ron's thoughts on the same:
"Conveniently, the bearing to George
Peak was only a
few degrees off true north and Polaris was
clearly visible, so it was
easy to find the right direction to aim. We tried unsuccessfully
several hours to get light from one end to the other. We tried
directions and detected nothing either visually or
the northern end they tried not only the LED but also headlights,
flashlights, and even a 'million candlepower' lamp. Brett and Tom
thought they saw something several times, but it never correlated with
the times when things were on or off on the other end. We
these sightings to headlights, campfires, and the like."
"We did not hear a thing on the red
band. It was totally quiet [but] I am quite sure we were pointing
right. I slowly scanned back and forth and up and down over and over
both when we were listening and when we were transmitting. My little
table worked really well, I could smoothly move the box left and right
and it was very stable. We did as Clint suggested and turned on the
receiver when he transmitted just on a chance that it would hear
something or respond to a laser flash, but we never heard the slightest
change in the receiver’s noise."
On that evening, despite several hours of trying, no signals could be
acquired, nor could the distant light from the south end of the path be
seen through an 8" reflector telescope set up at the south end.
As related by Gordon:
"After about two hours of attempts, we
decided to give up. We started packing up for the return trip a bit
after 10 P.M. If the hike up had been frustrating, the hike back down
was downright frightening. I guess there really was no great danger,
but I was carefully considering each step before gingerly trying it on
the loose gravel. I must have fallen at least a half-dozen times on the
way back, and sometimes my feet would just slide out from under me
again when I tried to get up.
"Ron and Brett were trying to keep the party together, an admirable
goal. But they had their hands full between Tom going forward
confidently and quickly in front, and me taking about five minutes for
each ten feet of progress in the rear. Things started looking better
after the initial steepest part was over.
"Often, all we could see of other members of the party was their
lights. They were all distinctive and we learned quickly how to
identify one another. Brett was using a red headlamp, I had a green LED
mini-flashlight, Tom had a flashlight and a headlamp, both a
bluish-white LED color, and Ron had a white headlamp.
"Of extreme value were the GPS 'bread crumb tracks' that constantly
showed us how far we were away from our outbound route. Goodness knows
our outbound route had not been one to recommend as a delightful hike,
but at least we knew it was mostly passable and would eventually lead
us back to the cars.
"We only found one of our glow sticks in addition to the one at the
cars, but its sighting was a cause for some celebration. We got back to
the campground a little after midnight with our bodies and equipment
mostly intact. The night sky was gorgeous [and] we spent some time
watching meteors and listening
bursts on an unused FM broadcast channel. Finally,
threw out sleeping bags and bedded down for the night."
At the north end Paul and his kin departed and because they lived in
northern Utah, they had only a two hour drive home. After packing
gear we drove most of the way down the mountain, stopping for the
evening in a clearing amongst lodgepole pines that we'd noticed on the
drive up because we had a 4-5 hour drive ahead of us and decided
that it would be safer to delay until daylight. Throwing sleeping
bags on the ground, we crashed there, under a starry sky, until the
In the morning, we packed up and headed the rest of the way down the
mountain. Emerging from the canyon into the Raft River valley we
couldn't help but notice that a dramatic change had occurred
overnight: It appeared as though much of the "muck" that had been
prevalent in the southern end of the path had moved northwards and was
now enveloping much of northern Utah. To the south, "Team Swasey"
awoke to a vista rather than a curtain of haze giving much of the
party their first
view of the surrounding desert. As you might have already
returned home safely after the adventure.
Obviously, we had to do more to determine
beforehand if the air was likely to be clear enough for a reasonable
chance of success. Of surprisingly little use was the weather
forecast: While it was useful in telling us when not
to try it, using the available data to determine if the air
was going to be clear enough over such a long distance optical path was
difficult. In hindsight, we should have realized the significance
of the high winds along the desert - but there, too, was a
contradiction: In the absence of wind, the clearing index is low
and haze accumulates, while with too much wind, airborne dust
After the fact it was realized that there was an important factor that
had exacerbated the poor conditions. Several months earlier, the
largest wildfire in Utah's recorded history had burned a large area to
the south of Swasey Peak. The denuded landscape now fell
victim to the wind's ability to raise large
amounts of dust and ash into the air and in the weeks following the
sections the Interstate highway along the eastern edge of the "burn
zone" had to be closed on several occasion when visibility dropped to
less then a car length. Later, Gordon recalled Brett's mentioning
that during the drive in, it seemed that much of the dust seemed to be
coming from the south, the direction of the burn area.
After this attempt we also took more heed to the fact that it would be
unlikely that good conditions were always going to coincide nicely with
schedules and occur on weekends. For future trips, we would keep
an eye on the weather
forecasts and mountaintop webcams - some of which could be used to
provide a limited
amount of information as to the clarity of the air over long
distances. Perhaps the most significant change in strategy was
that we should be prepared to go with short notice, taking immediate
advantage of favorable conditions: This, of course, meant that it
was likely that we'd have to take a day off work with little prior
warning - something that was going to limit the number of those who
would be able to go on the
Another thing that was learned was that despite the fact that the trail
and down Swasey was more difficult than expected, it was well within
our abilities and prior experience and
planning had adequately prepared those involved for the hardships
encountered - namely, route-finding in the darkness. While it was
somewhat of an encumbrance, the weight and bulk of the optical gear was
easily manageable - especially when distributed amongst four people.
If at first you don't
(October 3, 2007)
As the days and weeks passed, we couldn't help but
notice that the
mountains had begun to show dustings of snow in the recent storms,
offering warning that,
before too long, the higher mountains would soon become
inaccessible for the winter season. In preparation I bought a
set of tire
for my Jeep as it was expected that the shadowed, north-facing slopes
of the Raft River mountains would have already begun accumulating their
winter's snowpack. One unintended consequence of our plan of
being prepared to leave with short notice was that it caused a certain
amount of artificially-induced tension: There were several
discussions on whether or not the prevailing weather was good or bad
for our plans, plus there was the realization that if we waited too
long, the weather would close in and cancel plans for the year.
Top Left: A view of Swasey
(the highest peak on the right side) from the road. Notice that
it is visible this time!
Top Right: At the trailhead, Ron and Brett trying to
cram the needed gear into their packs.
Bottom Left: Turning the camera around, Gordon and
Brett preparing to depart.
Bottom Right: Swasey Peak - this time, in the clear.
Click on an image for a larger version.
On the evening of October 2 we got together on a multi-way telephone
decide our strategy: The weather looked to be pretty good - but
there was a large storm system circling about in the pacific northwest
that, it was predicted, would move into the area in 2 or 3 days,
probably dumping enough snow in to the Raft River mountains to make
them inaccessible by wheeled vehicle until the following summer.
Also of some
concern was the temperature which was predicted to drop into the
mid 30's Fahrenheit overnight with a high into the low 60's in the
day. This, coupled with the predicted "breezy" conditions, gave
worry about not only a recurrence of the previous attempt in which
visibility was spoiled by airborne dust, but also the practical fact
that it would be unpleasant to sit on an exposed ridge and hike down in
while facing fairly cool temperatures and high winds. Finally,
after much deliberation, we decided to go for it.
Departure and arrival of Team Swasey:
According to Gordon:
"We had a telephone conference the night before the
trip, and again the morning of our departure at about 7:20 A.M. to
decide if we should really go. The 46-mph gusts predicted on
were a bit daunting, but when all was considered, we decided to give it
a try. We were proud of leaving Ron's house before 9:30, hours
earlier than had been the case on September 15. This time the
consisted of Ron, K7RJ; Brett, N7KG; and the author, K7HFV. We
managed to fit into Brett's [Chevy] Avalanche... (Tom, W7ETR,
had been with us on the first trip was busy working and arranging to
close on a house in Wyoming.) The 'team' at the other end of
near George Peak would consist of just Clint, KA7OEI."
the north site:
"The visibility looked fair, not great, but as we
approached Delta, we could see Swasey peak way off to the west.
important, visibility to the north looked good. We stopped at a
food joint in Delta and ate our lunch on the road as we continued to
Swasey Peak, which came into clear view. We remembered last time
turnoff we could not see the mountain. We talked to Clint a time
on the cell phone to update him. As we suspected, we could not
him from about where we turned off the main highway till we were on
the ridge at our final site. We were both in remote parts of the
with poor cell and ham radio repeater coverage. I suspect, had
mission been to talk to Clint on two meters from the base of Swasey
peak, we may have been able to find some linkup, but getting up the
mountain was far more pressing an issue and we knew we would have a 2
meter simplex path where it counted."
Because I didn't have to hike up a mountain, my departure time was a
later than that of Team Swasey's - a schedule that would still allow
time to get to my destination. As I sped north I could see
that while there was some haze in the air, it looked more promising
than it had during the previous attempt. I was also keeping
an eye on
the tops of the mountains and couldn't help but notice that the
snowline seemed to be descending as I went north: I couldn't
decide if this was simply an optical illusion, due to recently-cooler
temperatures inhibiting the melt off, there having been more snow to
begin with - or a combination of the three.
Before too long, I had
a view of the Raft River range and I noticed, along the top and in the
deeper couloirs, thin ribbons of snow: These remnants from the
storms, while not unexpected, made me glad that I'd
brought a set of tire chains. Knowing how remote the destination
was and how difficult any attempted rescue might be were I to run into
trouble - either from a mechanical breakdown or due to a freak storm -
I'd packed a week's rations of food and water, a camping stove, an
change of clothes, a second pair of boots, several layers of coats
and jackets, and two sleeping bags: If the worst happened, I
might be miserable and unhappy, but I would be able to wait several
Soon, I found myself heading up One Mile canyon south of Standrod, Utah
on the north slope of the range noting that the
ground was mostly dry. It wasn't until above 7500 feet or so that
I began to see larger patches of snow in the shadows - but the road was
still in pretty good shape, albeit a bit muddy in a few spots.
One of the features of this road is that it is quite rocky - a factor
that can actually improve travelability in snowy and icy conditions.
The road continued up to a pass, took a sharp left turn, and
continued upwards, hugging a west-facing slope: Up
to this point the road is quite passable by
ordinary 2-wheel drive vehicles, but it soon becomes a 4-wheel
drive-only road. After traveling only a few
hundred yards I met someone coming the other way, requiring me to back
road 50 feet or so to find a spot wide enough to allow two vehicles to
pass - an opportunity
that I used to query the approaching driver about the road
conditions above: He'd gone only as far as the "meadows" which he
said were somewhat
- but that he'd heard from someone else up there that there may be some
drifts on the road in the
pines above that.
Soon, the road began to climb
steeply along open, rocky ground on a northern face and it was along
this portion that I
first encountered enough snow to require a slight detour to
avoid that which had drifted into the roadway. After topping the
ridge and dropping slightly into the meadows, I experienced a little
more snow and some mud, but I had little trouble. After crossing
meadows I started into the pines where a bit more snow drifted
into the roadway, but it was rather packed and shallow so it posed no
problem. Heading up the final slope to the highest ridge I
group of vehicles coming down - some of them towing trailers: One
of the drivers mentioned that the road along the top was badly
drifted, but the strategy of staying on the ridgetop itself
and avoiding the road altogether had prevented problems.
Continuing, I soon topped the ridge and drove along the
road at about 12:30 in the afternoon. This road, although public,
crosses a parcel of private ranch land - but this time the two gates
bounding this section were open and just after exiting this portion of
road, I ran across the first bit of snow that caused a problem.
After the first unsuccessful run across this patch, I backed
up, put the chains on the front drive wheels, and successfully crossed
After driving a few hundred feet along the ridge top I noticed that
road below was, once again, clear so I decided to drop from the ridge
back down to
the road only to find
firmly stuck in a snowdrift about three feet from the road and upon
investigating, I noticed with chagrin that my Jeep had high-centered on
snow. After about 90 minutes of crawling
around under the car, removing as much snow as possible and
unloading the vehicle to raise the frame, I placed a strip of plywood
(brought along to form part of an equipment table)
under the slipping front drive wheel: Soon, the spinning wheel
gained purchase on the plywood, raising the car onto the surface of the
snow, allowing the remaining pack to clear the undercarriage and the
Jeep broke free of the snowbank. I then walked
along the road, scouting for the best
path and noted that there was a small patch of snow that I could not
avoid. Returning to the Jeep I took a run at that patch, breaking
through it and, with the vehicle still-unloaded, circled
around the snowbank and parked on the ridge above where I'd been stuck.
Top Left: A view of the setup
at the north end with George Peak itself in the background.
Top Right: Brett and Ron, packed up and making the
Center Left: Brett demonstrating the steepness of the
hill that Team Swasey had to climb - and descend in the dark.
Center Right: Looking back down at the trailhead.
Bottom Left: Gordon, writing in the visitor register
found in a mailbox on the summit of Swasey Peak.
Bottom Right: Clint, trying to eat the rehydrated
dinner, having forgotten to bring any silverware...
Click on an image for a larger version.
At about this time, a rancher on horseback appeared from the south
face of the mountain. Making a sweep of the range he was looking
for the last of the cattle that he'd been running up there over the
mentioned that I'd seen two head that, before I'd gotten
stuck, were to the west of me - but were now about
a half-mile to the east and up the hill. When asked about the
being open on
the fence he said that at this time of year all gates were opened to
allow the cattle to roam freely so that they could seek shelter
they were - with the sorting out of whose cattle belonged to whom to be
left for later. He was wondering what I
was doing on
a ridgetop at this time of year - especially because it was clear that
I wasn't one of the throngs of bow-and-arrow hunters present on the
mountain - so
I explained to him, pointing at the
barely-visible outline of the Fish Springs mountains in the
distance. After a friendly 10 minute conversation he moseyed
off in the direction of the cattle.
After changing into dry clothes and boots I spent the next half-hour
lugging the previously-unloaded gear across the snowbank and reloading
the car. Knowing that I would need to be able to retrace the path
darkness I set up a series of cairns
to mark the route
the spot where I'd originally chained up to leave the road for the
ridgetop by crossing
the small snowbank.
Traversing the snow-free top of the ridge I paralleled the road,
eventually arriving at the very spot from which some pictures had been
during the late August exploration trip. This place, although
miles east of George Peak itself was, by direct observation and
examination of the pictures was known to
have a line-of-sight path to Swasey Peak. What's more, having
the photos, I already knew where Swasey Peak was in relation to the
other topography so there was relatively little uncertainty as to
where things had to be pointed. Finally, having already gotten
stuck that day, I decided not to tempt fate by traversing the ridge any
I now began to unload the gear
and set up.
Team Swasey begins the ascent:
In Gordon's words:
back at at the Raft River mountains...
"We stopped in Delta to procure some of
the finest food
that a McDonald's can provide, and then continued to the
trailhead. We had talked about the possibility of hiking a
different route, approaching the summit from the southeast rather than
the northwest, particularly if the northern slope was
looked at the beginning of the alternate approach as we passed it on
the road and concluded it started out quite passably although how the
route got around a headwall was something not immediately
decided, though, to stick with the known [route] as there appeared to
snow problem anywhere on the mountain.
"We reached the end of the road, packed
our packs and started hiking
just after 2 P.M., a full three hours earlier than on our September
trip. The temperature was very comfortable, in the mid
route involved getting to the summit ridge near a saddle northwest of
the summit. We tried a different approach than the [expletives
one we had used in September. We took a more northerly path,
the rim of a deep canyon, and started climbing toward the ridge on the
side of a draw furthest from the peak. We all agreed that this
although a bit longer, was far more pleasant than its September
counterpart. There were long, walkable strips, clear of mountain
mahogany and pinion, and only occasionally did we have to duck down to
pass under a tree branch or unsnag a pack from grabby branches.
"We left a glow-stick on a tree just
short of the saddle, hoping it would help guide us down later on our
descent in the dark. We had left another back at the truck. The saddle
itself was quite dense with trees and took some maneuvering to cross.
Just as we were about to start climbing toward the summit we heard a
very loud roar that sounded like a cross between a hurricane and a
steel foundry. Just as we began to wonder what sort of disastrous
weather was striking, we spotted a black, military, supersonic jet
rapidly receding west of us. No one recognized its model. (Clint
remarked, 'You probably weren't supposed to see that.')
"There was no getting around the fact
that the ridge was very steep. We
looked carefully for easier routes than we had found in September, and
in a few cases found some segments that worked better, but the bulk of
our route followed hints of a trail that we had found in September. The
most difficult part was probably the ascent, over steep, loose gravel,
leading to our September operating position. I did better than before,
only having to be rescued once."
At the north end, I'd set up the
telescope and radio in preparation for the arrival of Team Swasey at a
place that had line-of-sight coverage to my location. Having
do but wait I walked around, took a few pictures and then decided
that having spent much of the day driving followed by several hours of
digging the car out of the snowbank was likely to make someone
For this late lunch I chose a freeze-dried entree - a wild rice and
mushroom dish - rehydrated with
boiling water. While the water was heating I rummaged around and
discovered that I'd forgotten to bring any silverware so I ended up
extruding the food from its plastic pouch: It was a messy method,
worked (see Figure 6.)
While I was trying to eat my dinner, Ron called me on the
Top Left: Ron, talking to
Clint via 2-meter simplex over the 173-mile path.
Top Right: Brett, attempting to signal from the Swasey
Bottom Left: A view to the north from Swasey Peak.
Bottom Right: A view to the south toward Swasey Peak
Click on an image for a larger version.
"The hiking from this point was much
easier and we soon came to a second likely position about 200 feet
higher in elevation. It seemed to meet all the requirements: a drop off
to the north, a reasonable amount of flat rock to set up on, and a
location east of the ridge to shield us from expected west winds. Ron
gave Clint a call on '54 simplex and got an answer, so we had at least
a two-meter path over the 173-mile course. Clint reported the copy
wasn't terribly good, but we could get through on the rubber duck
antenna if we chose our position carefully.
"Should we try for something higher? We might have a better chance of
success higher, but then we didn't look forward to a longer hike back
in the dark, or having to operate in high winds on a cold night. It was
between 4:30 and 5:00 with at least two hours left until sunset, so we
decided to explore a little further without our packs. We thought that
if the two-meter signal improved dramatically near the summit, the
light path might also. If the two-meter signal didn't change much, then
we would be more confident that the path from this position was as good
"Uphill from this point, the going was relatively easy. We quickly
reached the top of the immediate hill and saw that it was not the
summit. We could see a flat face that was practically vertical and way
above us. It looked quite daunting until we moved a few feet closer and
saw that it was not as far as it first appeared and there was an easy
way up. Brett and I headed on to the summit. Ron initially thought it
would take too much time, but joined us when he saw how quickly we
reached the top. The trip from our proposed operating site had taken
less than 45 minutes.
"On top, we found a relatively new mailbox that served as the housing
for the summit register. The last party seemed to have made an entry in
late August. I logged us in with a one-sentence description of our
purpose. Brett found an interesting message [what appeared to be 'XE5' written upside-down] that had
spelled out using small rocks. Ron tried contacting Clint on his H-T
and concluded that the signal quality Clint was receiving was, if
anything, worse than it had been at the lower operating position. We
decided we would be happy with the lower site. Clint tried sending us a
sunlight flash reflected by the mirror in his compass. Brett was sure
he saw the flash several times and I saw a flash that seemed to
correspond with Brett's sighting at least once."
"...[Having] dropped our stuff and [gone] to the
summit... we did not find any better places to set up. The
have been beautiful, [as] it had a commanding view in every direction,
it was exposed and windy [and] we were concerned that at night it would
intolerable with the wind and possible cold. From the summit we
to Clint on 2 meters and the signals were no better from the top than
at our site [and] that made us a little more confident that our site
"We tried flashing each other with mirrors.
Gordon thought they each saw flash or two but I never saw a flash nor
did Clint see one from us. The visibility was good, [but] not
were not completely surprised that we couldn't see a flash."
At the north end, using the full power of the 8" reflector telescope
and wide-angle eyepiece I
tried in vain to spot any hint of a mirror flash from the south
end. Practically speaking, the south-to-north "mirror flash"
attempt was disadvantaged as compared to the north-to-south path
because of the sun: From my end, I was looking toward the
sun and even though it was off to the south and west, this angle
tended to illuminate the haze and worsen glare, causing increased
of the already-feeble mirror flashes. At the south end the sun
was slightly behind the party requiring that a rather steep mirror
to reflect light northwards - something that not only makes aiming a
bit more difficult, but it reduces the effective area of reflection of
"We returned to our site and started setting up.
tried the sunlight flash again, but were unable to spot anything
reliably from Clint's direction. Ron started hooking up the
transceiver and its associated electronics while Brett and I set up our
2-meter beam and established better-quality communication with
Ron's table worked nicely on the bedrock and the adjustable-length legs
made it so we could get the elevation within the range of the
adjustment on the transceiver box itself. On the radio end of
things, Brett and I lashed the WonderPole to a dead tree with cord and
duct tape rather than using the rock pile and guy rope system we had
used in September. We found that in addition to being able to
Clint, we could also hit the '62 repeater where we had a QSO with Brad,
N7SWW, in North Ogden.
"During the setup we had heard the
wind roaring strongly to the west of us, but our location, fortunately,
provided good shelter. At this point, though, the wind began to abate.
We hoped it would also take a break when we were ready to hike down. As
it began to get dark, we looked carefully at the northern skyline to
spot the pattern of mountains that would show us Clint's position.
"While we were looking we saw a
bright, reddish light well above the
horizon. [Audio clip, 2:58, MP3,
We guessed first it might be a plane's landing lights. However, it
seemed too red and too stationary. It remained the brightest object in
the sky for 5-10 seconds, then faded away over about one second. It had
been in the general direction toward Clint, so we asked if he had seen
it, but he had not. Before the evening was over we saw over a dozen of
these strange, transient lights. They appeared sometimes singly and
sometimes in pairs. They popped up at various azimuths, although the
most common were northwest and slightly east of north. We never came up
with a plausible explanation of their origin. We had seen nothing
similar on the September trip to the same mountain.
Top Left: Brett and Gordon
setting up the "WonderPole" - a portable, fiberglass mast that was used
to hold the portable Yagi aloft. Brett's large binoculars - used
to spot the light from the north end - are also visible.
Top Right: Gordon, talking to Clint - obviously pleased
that the signals were much better with the beam than with the
Bottom Left: Ron, getting the optical transceiver set up
on the small "light table" set on the ground.
Bottom Right: Set up and ready to go, the optical gear
at the George Peak (north) end of the path.
Click on an image for a larger version.
"Elaine, N7BDZ, had driven out on
[Interstate]-80 to see if she could see anything from either end of
this experiment. She calculated that our light path would cross the
road very close to the 'tree'
sculpture. When she came on the air, she had good communication
with Clint on '54 simplex. We could hear her with a full quieting
signal, but she could not hear us. She was able to see Clint's green
laser pointer, but could see nothing from us. This might be explained
by the fact that her distance to us was [slightly more than] her
distance to Clint [which put us slightly below the visual horizon] plus
the fact that we were running less than one watt to conserve batteries.
"The north star gave us a good reference for the right azimuth to Clint
as his bearing was just 2-3 degrees west of north. It turned out that
there was a cluster of lights (likely mercury vapor) visible on almost
the right azimuth. Ron could make a preliminary receiver adjustment by
peaking the receiver on the hum from the lights, then raising the
azimuth to the skyline. We could hear a bit of our own signal owing to
reflection from treetops near the lower edge of the beam."
Prior to sunset, I'd set several "optical beacons" along the ground
in a line that extended several hundred feet in the direction of
Swasey Peak. During the September attempt, we'd forgotten to lay
out any visual references and once it got dark, the landmarks (distant
mountains) disappeared, making it a bit less clear as to exactly where
we should aim. These beacons
were simply green LEDs connected to 9-volt batteries through
resistors: While these LEDs were quite dim, they were easily
visible in the darkness.
As twilight passed we began in earnest to spot each other's
lights. On my end, I used my 8" reflector telescope - along with
a wide-angle eyepiece in a 2" mount - to try to spot the light from the
far end. Team Swasey's spotting gear was more modest: Brett
had brought along a large pair of tripod-mounted zoomable binoculars
and there was a lightweight 60mm Meade refractor telescope to allow a
second set of eyes to scan for light. As the evening progressed
we threw whatever photon sources we had in each other's
direction: In addition to the optical transceiver, I had onhand a
1/2 million candlepower spotlight as well as an assortment of red and
green laser pointers - and I tried all of them - but nothing was
spotted at the
far end. At the Swasey end, the arsenal of light sources was
smaller, but efforts to shine light to the north and be spotted were
no less earnest.
After Elaine was able to spot my light sources I decided to travel
about 3/4 of a mile west along the range (leaving behind the majority
of the gear) to a location that was completely free of any obscuration
by intervening terrain: Although the site that I had chosen
should have had a line-of-sight path with Swasey Peak - especially with
atmospheric refraction working in our favor - I tried this second
location in the event that something odd was happening in that the
supposed line-of-sight path was not, in fact, extant. After
several minutes of signaling attempts (with lights) I gave up and
headed back to the original site.
A final search for enlightenment:
Nearly ready to give up on this attempt I made yet another scan with
the telescope while Ron moved the transmitter at the Swasey Peak end
about, scanning both azimuth and elevation. After several
minutes I caught a glimpse of what I thought was a flicker of light,
just at the edge of perception, so I stopped moving the telescope and
had Ron repeat the last several movements: The dim light came and
went. Working more slowly, I had him move it back - and the light
reappeared and I centered it in the telescope's field of
view. To verify that I was, in fact, seeing what I hoped to
see, Ron turned the light on and off while I relayed, via radio, when I
saw it appear and disappear: I could hear an exclamation of
from Brett and Gordon in the background audio when Ron's next
transmission related that I was, in fact, seeing their light...
- Seeing the light.
that includes the moment at which the
sighting of Team Swasey's light was verified. Unfortunately,
background noise from the optical
receiver makes it difficult to understand at times so a transcrption is
provided below. (0:43,
Clint [via radio] Ok, hold - stop
that. (pause) Hold it there, hold it there, hold it there!
Uhmm, I can barely see it. (another pause) Uhmmm... Azimuth
- I lost it...
it's back. There it is. Elevation... Elevation...
Gordon: I can't see him - is anything happening?
Ron: Well I'm hearing something here, I...
Clint [via radio]: I'm not sending anything right now.
Clint [via radio, interrupting Ron]: Turn it off.
Ron: I can't find the switch!
Clint [via radio]: Turn it off...
Ron: I can't find the [beep]ing switch!
Clint [via radio]: I need you to turn it off and on.
Ron: (There's a click) There, OK.
Clint [via radio]: Off... (click) On...
(click) Off... (click) On
Ron: How about that!
(Sounds of jubilation!)
Spending a few more minutes to visually peak the pointing of Ron's
transmitter, I had him modulate it with a 1 kHz tone while I set my
receive system in the "Audible S-Meter" mode and began scanning through
the darkness. With only the dim, green LED beacons and the
pointing angle of the telescope, it was difficult to judge exactly
where I should aim, but as I moved about, I could, amongst the thermal
noise's deflection of the audible S-meter, discern a very slight peak
- but it was almost too small to be sure that I was really hearing
I then had Ron shut off his transmitter while I turned mine on
modulated with a 1 kHz tone while he relayed, via 2 meters, his
audible S-meter: Because his receiver was already
in my direction, it was hoped that he might be able to hear me better
than I could hear him.
Later analysis of the log recordings showed that the transmitter was in
"variable tone mode" and a 1.4 kHz tone was
inadvertently transmitted from Swasey on this occasion instead of the
greatly reducing the sensitivity of my S-meter during this particular
phase of optical alignment and explaining why I found it so difficult
to "see" his signal with it.
About the aiming procedure, Ron relates:
Top Left: Ron,
operating the optical transceiver from Swasey Peak.
Top Right: 30 second time exposure of Ron, operating the
transceiver with illumination from a red headlamp.
Bottom Left: Clint, configuring the optical transceiver
at the north end of the path.
Bottom Right: A front view of the optical transceiver
operating. (The white light above the red lens is a headlamp
being worn by Clint. This is the last picture taken by the camera
before it was destroyed by a gust of wind.)
Click on any picture for a larger version.
"With Clint looking in his scope, I
slowly rocked the
beam back and forth to tweak it in. I don't remember the sequence
of testing, but Clint has devised a clever S-meter reporting scheme
that makes it fairly easy to align the lights. By relaying a tone
from the received over the 2 meter link, the person on the light
transmitting end can swing their light back and forth and hear the tone
change. By tweaking for the highest pitch tone, one can fairly
easily align the transmitter. We went through this process and
carefully acquired signals and aligned the pointing.
Listening to the S-meter tone relayed from
Ron's end, it took only a
few 10's of seconds before I heard a definite deflection
pitch of the audible S-meter from his end, and hearing the meter
modulate when I keyed my own light verified what I was
hearing. After several more minutes of back-and-forth signal
we managed to squeeze a few more dB out of each end of the link by
careful aiming and we were now ready to try an MCW (Modulated CW, or
exchange. Why use Morse? Simply put, it is an effective
digital narrowband communications scheme that requires a minimum amount
equipment - an important factor if you are carrying everything on your
were very weak, we could only barely hear each others tones, but they
were absolutely there. Since we could hear the tones we were
able to make an official QSO exchange with each sending call letters
and grid squares. We [sent] the code by turning on and off the
LED [and because] the LED was always being modulated with a steady
tone... [what] we heard in the speaker was the... [code] being sent.
did not get a tone because of simply detecting the presence or absence
As it turned out, Ron was able to copy the MCW that I was sending
rather easily - even though it was quite weak. In turning the
link around it became apparent that Ron was hearing me quite a bit
better than I was hearing him, but I was still able to make out what he
was sending amongst the noise. Having completed a 2-way Morse
we then decided to try to see if it was at all possible to send voice
back and forth. Talking very slowly, Ron was just
hear my voice and tell what I was saying - albeit with some
difficulty. In coming the other direction, however, I could tell
only that a human voice was present in the background noise, but there
was little hope in being able discern what was being said.
Segments of the recordings made during this event may be found
farther down this web page.
According to Gordon:
"Somewhere in the exchange, Brett
discovered that he really could see Clint's LED through his binoculars.
He had initially aimed the binoculars based on a computer-simulated
picture of what the skyline should look like. It turned out that the
real bearing was just barely enough further west to be out of his field
of view. The discrepancy may have been due to the picture's being based
on the Swasey Peak summit rather than our spur-of-the-moment choice of
operating position. A few other experiments were tried. Clint sent some
pre-recorded slowscan [television, or SSTV] images that we recorded on
a digital recorder from the receiver output. They would be decoded
After the fact, I reviewed the "open mic" audio recording from Swasey
Peak and it turned out that Brett was questioning whether or not George
Peak was the "bump" that he could see, or if it was a point beyond
the bump that was, in fact George Peak: Early in the
recording Brett reported seeing the flash of light in a point in space
"above" where he interpreted George Peak to be according to the
Now that the exchange had been completed I tried a few modifications
if I could improve the receive sensitivity, including removing some of
the photodiode masking that had been applied to reduce receiver
beamwidth: It was difficult to tell if this actually helped or
if conditions improved very slightly, but the MCW tone seemed to be
slightly better in the back-and-forth exchanges that followed the
adjustments - or was it just wishful thinking?
Finally, we decided that we'd done as much
as we could with the high-power LEDs so, for Ron, I started playback
of a recording of the theme song of the cult classic movie, Dark
- a tune that Ron instantly recognized after the first few
chords. After this, SSTV and a few more music and audio clips
were sent. The entire exchange - both transmit and
receive - had been recorded to .WAV format using portable digital
audio recorders and using this format guaranteed that the audio
would be losslessly recorded so that it could be analyzed later -
including periods of constant tones that we had sent. These
recordings could then be used to determine
something about the
signal-noise ratio of the signals that we were exchanging as well as
the amount of scintillation caused by the atmospheric propagation over
such a long distance.
Finishing the experiments with the LEDs we decided to see if we could
the distance with Lasers. On several previous occasions - such as
our second 107 mile QSO - I had
successfully used a Laser pointer module with my 8" reflector
telescope. Even with its narrow beamwidth, aiming of the Laser
was quite easily done as I simply removed the eyepiece and replaced it
with the Laser module: Only a very small amount of tweaking of
telescope's elevation was required to peak the signal. On this
however, no sign of the Laser was heard via the audible S-meter system
or seen through the binoculars at Swasey. Ron tried going the
direction with his Laser pointer, but no evidence of signal was
detected in that case, either.
Heading for home:
At this time - at about 10:15 PM - we decided that we were done, so our
respective groups started tearing down and preparing to leave. I
took a few more pictures and while doing this a gust of
wind came up: As I
lunged to keep the optical transceiver from sliding off the table, the
tripod with my small point-and-shoot camera fell over, lens-first,
destroying it: While annoyed, I'd realized that I could
have saved only one piece of gear at a time - and I was thankful that
it was not the expensive SLR that had been on the tripod at that
moment! It took about an hour for me to tear down the
equipment, pack, rearrange the gear in the car, and depart. At
the time that I left, the wind was picking up a bit with the
temperature in the low 30's F (near 0 C) but the sky was almost
providing a spectacular view of the heavens being completely free of
pollution and above much of the atmosphere.
While I was packing my gear, Team Swasey had yet another challenge
ahead of them.
About the descent in the darkness, Ron said:
"Getting down the ridge in the dark was
probably at least as unpleasant as it had been on the September trip,
but it helped to know from the previous experience that, even at a
seeming snail's pace, it was possible to get back in a reasonable
length of time. I think we all took a few spills on the section that is
horribly steep over loose scree. We had to contend not only with the
steepness and looseness, but also the wind. It had not granted our
request to stay benign during our descent. Our packs sometimes acted as
sails and, at one point, Brett was blown over while standing still. At
least we could commend the weather service on their accurate prediction
of the gusts.
"Following our GPS track from the uphill trip, we often found ourselves
going in directions that seemed totally contrary to what common sense
would have dictated. The trees were dense enough and the night dark
enough that we could see little of the general terrain around us. I
noticed that Polaris seemed to change direction regularly over a plus
and minus 90-degree range. Without the GPS 'bread crumb' track we might
well have wandered aimlessly until dawn.
"Once we were past the saddle, things went much better than on the
September trip. We almost missed our glow stick, passing within 50 feet
of it, but spotting it improved our confidence level considerably.
Through the trees, Brett and Ron both had missing segments in their GPS
tracks, but between the two we found most of our outbound path. We
spotted the glow stick at the truck early enough for it to be helpful."
"... It took about 20
minutes to pack everything up and head off the mountain. The trip
down was equally difficult as the trip up [because] it was very steep
coupled with being totally dark. We could see absolutely nothing
without our flashlights and we would have been hopelessly lost without
the GPS 'breadcrumb trail.' I fell a number of times, mostly from
my feet slipping out from under me, but the trail was so steep that my
butt didn't have far to fall. We had to push through the trees
near the saddle and it was as miserable as we had feared. We were
by then so it made it even worse... but, eventually we got
through. When we got to the far side of the saddle away from the
awful trees, we still had a long hike back to the car [and] we were
tired and ready for it to be over, so the last leg of the trip seemed
endless. When we got back to the car, we decided to drive back
home instead of sleeping in the wind. We did stop a few times
along the road to take naps. Maybe we should have stayed the rest
of the night at the trailhead [and] next time, I would. I don't
know when we got home, [but] I think it was around 6:00. I went
to bed when we got home and went to work about noon."
It should be mentioned that even if Team Swasey did not
have the facility of the GPS to guide them, they were prepared
equipped to wait until daylight to complete the return trip down the
mountain if necessary. It should go without saying that relying
on any single
navigational system in such situations is not a good idea and that
should always have a backup plan!
Top: A view toward the Raft
River Range from a point near Swasey Peak. The insets show the
computer simulated view, plus enhanced versions of the real-life view
(from a 16 bit TIFF image) with the salient features outlined.
Bottom: A contrast-enhanced view toward Swasey Peak from
the Raft River
Range. The insets show not only the computer simulated view with
the location of Team Swasey, but two real-world images from different
dates. Notice the difference in the amount of refraction.
Note: In both sets of images, the viewer's elevation in the
simulated view was exaggerated to more closely approximate the effects
of atmospheric refraction.
Click on an image for a larger version.
Fortunately, my trip down the mountain was not nearly as eventful as
the ascent had been: I easily found my line of cairns in the
darkness and crossed, without incident, the patch of snow that had
required that I chain up in the first place. Following the
now-familiar road down the mountain in the darkness I soon found
myself below the meadow, where I finally removed the tire chains.
While I had been prepared to throw a sleeping bag on the ground and
snooze until the morning, I wasn't as tired as I expected that I would
be so I continued onwards, past the metropolis of Standrod, along the
state highways, and onto the Interstate.
By the time I got to Brigham City, though, I was ready for a few hours
so I pulled in a rest area and closed my eyes for three hours. At
AM, I woke again and, ahead of the morning rush hour, and arrived home
after 6 AM - about the same time as Team Swasey. Before napping
I decided to dash off a preliminary version of an account of the
previous day's events while it was still fresh in my mind and while
doing so, I heard Brett appear on a local 2 meter repeater reporting
success in both the lightbeam communications and a safe return home by
all team members.
Initially, there was some concern about the weather conditions:
The forecast seemed unclear as to whether or not the Raft River range
would get rain and/or snow the following morning (October 4) and I
really did not want to get caught in an early-winter storm atop a
remote mountaintop - even if I was prepared for it!
expressed it this
It turned out that the weather front that threatened the
Raft River range didn't really do anything until Friday, but in such a
remote area, you have to play it safe!
"The week or so before the event, the weather was
pretty bad. We had had a big snowstorm that actually came down
into the valley. Nothing looked good about the weather [and] I
was getting discouraged and then I started to fret about the prospects
of going up on a mountain in the awful cold and wind and have to be
able to stay warm enough to operate equipment and make technical
decisions... My fingers and toes were numb just thinking about
it. Also, I thought about the steep hike down the mountain in the
cold and dark and all the things that could go wrong and it started to
get to me. For a week before we went, I really was stressed
[and] I let it get to me in a big way. I was disappointed
in my attitude because I just love these sorts of adventures, they are
a wonderful mix of a fun outing and technology. I was wanting
someone to decide that we shouldn't go, but, fortunately, everyone had
a much more realistic view and realized that the weather was not going
to be that bad, and if it really turned bad, we'd simply come
home. Thank goodness for leveler heads!"
About the "seeing conditions":
In retrospect, we realized that while the air was fairly clear during
this expedition, it has
to be extremely
clear to guarantee good visibility over such a long path. In
photographs from the August 25 trip and comparing them with those taken
on October 3 (see the photos in Figure
we realized that the clarity
along the overall path was
about the same - although the density of the haze seemed to be more
uniform during the latter event: In looking out across the
to be less hazy on October 3 than it had been during our exploration
trip in August, but the photographs reveal about
the same amount of obscuration of detail in each case. The exact
of the haze is unknown, but it is suspected that, as before, some of it
was due to windborne dust - plus some smoke from still-burning
The photos in Figure 10
what was being seen at the time and in
each case, the insets contain both computer-generated simulations of
the scenery showing the locations of the opposite end of the path in
addition to contrast-enhanced portions of the image to bring out subtle
details. As it turns out, on October 3 neither end was very
visible with the naked eye and it was only through extreme contrast
exaggeration of the original (non-JPEG!)
digital images that
details of the far end were even visible. (The
insets contain contrast-enhanced images from raw imager
addition, the inset images taken of Swasey Peak contain at least five
images having been "stacked" using an
astronomical image-processing program to further reduce noise.)
Is it a record?
While the "undisputed" record for a 2-way, direct optical
optical communication is still a 1894 heliograph exchange of just over
miles, this is believed to be the longest-distance all-electronic 2-way
ground-to-ground based communications using only "gray matter DSP" and
not involving any sort of special, narrowband technique, weighing in at
just over 173
miles. It is unfortunate that the clarity of the air prevented a
2-way voice exchange but it is expected that further enhancement of
the gear plus better conditions will, some day, allow such a
communications to be completed.
Every time we have gone afield with the optical gear we gain both
experience and insight as to how to improve our operation. In my
opinion, our past outings had given us just
with the equipment and the art to have lead to the success of this
adventure and, as with any complicated endeavor, one cannot have too
This isn't to say that things can't be improved: In discussions
since this event, a few things have been brought up:
- Some sort of sighting system. This could be as simple as a
"sighting tube" or a pair of posts that function like a gunsight.
While I've considered adding this from the beginning, it's hard to
decide exactly how useful or practical it might be. In this case
the distant LEDs were too dim to be seen with the naked eye, so any
simple sighting system would have been useless for direct observation
of the light from the far end: It was the
electronic aiming system (plus the large telescope) that provided the
critical aiming. A sighting tube may be useful in referencing
known objects (distant lights, stars, etc.) to provide an approximate
point, however. What is useful is the fact that one can
usually see the beam being emitted from the transmitter due to Rayleigh
and dust scattering - and this can provide an aiming aid.
- We are still trying to determine the reason for the disparity in
the signal levels in the two directions. It is known that the
optical transceiver used at Swasey has about 77% of the luminous flux
output of the optical transceiver used at the Raft River end - a
difference that correlates to a decrease of about 2.3dB of audio
recovery. It does seem, however, that the majority difference
two ends was due to the receiver used at
the north end having slightly worse noise performance than the one used
at the south end.
- It should be possible to bring the performance of both
transceivers up to par with each other by further optimization of the
optics - notably a precise modification of the secondary lens in the
transmitter used at Swasey Peak.
- It should also be possible to extract a few more dB of receiver
performance out of both receivers through the use of careful
component selection and design refinement.
of the received signals:
Because waveform-accurate (non-compressed) digital recordings were
made, it was possible to go back and analyze what was recorded at each
end to glean more information out of the received signals than that
which could possibly have been divined at the time of the event.
Of particular interest to us is the amount of scintillation that was
present on the received signal and, somewhat related, the average
Top: Typical scintillation observed on a 1kHz tone as
received at Swasey Peak over the 173 mile path
Bottom: Close-up view of a portion of the above, showing
Click on either image for a larger version.
Scintillation manifests itself as variation in the strength of the
received signal - a result of light's traveling through an imperfect
atmosphere. Scintillation can be caused by a number of factors,
- Variations in the refractive index of the atmosphere. Most
of this is due to "bubbles" of air of different temperatures moving
about in free space. Because air of different temperature has
different densities - and because the refraction caused by the air is
related to its density - light traveling through these "pockets" is
"bent" very slightly.
- Scintillation due to coherence resulting from the very small
subtended angle of the distant light source - a phenomenon referred to
as "local coherence." At large distances,
the small apparent size of the distant light source can, for all
purposes, be considered to be a point source. With such narrow
angles, even noncoherent light can "temporarily" achieve a degree of
coherence - a property that can subject it to the same type of
constructive/destructive interference observed when a coherent light
source (e.g. a Laser) is used.
Scintillation is one of the major factors that complicates the
implementation of any free-space optical communications system:
amplitude distortions observed at the receiving end tend to disrupt
information transmitted across such a link, require a number of
measures such as very high signal levels, amplitude-independent
modulation schemes (i.e. FM-based) variations of forward error
correction and data interleaving methods to name a few.
For our experiments we chose amplitude modulation as it is both
simple to implement and very efficient in terms of minimizing receive
system bandwidth and maximizing sensitivity - plus it lends itself to
being able to measure the
scintillation appearing on the received signals. During our
testing our transmissions included sections of constant-amplitude,
precise-frequency tones, something done specifically to provide a
reference for later analysis. Several 30 second clips of recorded
tones were analyzed and it appears
as though the amount of scintillation was equal for the north-south
path and the south-north path - not a surprise. Because the
signal-to-noise ratio on the signals received at Swasey Peak were
somewhat better, it is those that are displayed here.
Because the signals were quite weak, it was necessary to
bandpass-filter the recordings during analysis to make the waveform of
the 1 kHz tone more visible amongst the noise. With signals as
weak as these, analysis is rather awkward: Using too-narrow
a filter the finer details are lost, but too-wide a filter, the
signal itself becomes diluted by noise, making the displayed waveform
meaningless. In addition to these conflicting requirements,
amount of scintillation is made even more difficult as random noise can
short-term constructive and destructive variations in the resulting
amplitude leading to confusing results.
To facilitate analysis, different amounts of filtering were used to
provide a general "feel" of the amount of scintillation: For Figure 11
, the top image shows 20
seconds of the signal, filtered through a filter a 2Hz bandwidth. For
the bottom image, the audio was run through a
-order Bessel filter (implemented in software) that had a
bandwidth of +-80 Hz. Note: Some of the apparent
scintillation rates in Figure 11
are a direct result of the bandpass filtering. Only changes
occurring at a rate slower
than that imposed by
filtering should be considered - that is, about 1/2 second for the top
image, and about 12.5 milliseconds for the bottom image. The
audio represented by the top waveform of Figure 11 has been amplitude
normalized for full-scale
16 bit representation, and the lower waveform is a portion of that same
As can be seen from the top image of Figure
, the maximum amount of scintillation over the 20 second
period displayed is approximately 6dB and was a typical long-term
the bottom image of Figure 11
with its wider audio filtering, the effects of the filtering itself can
clearly be seen as "ripples" but one can also see the shorter-term
effects. In this case the apparent scintillation depth is in the
10-12dB area - but the precise depth is difficult to determine, owing
to the fairly low signal/noise ratio of the receive signal in the first
place, coupled with the effects of the filters.
When observed "by ear" it is fairly clear that both the magnitude and
rate of scintillation is quite low - far lower than that observed over
both the 15 and 107 mile clear-air experiments. This result is
somewhat surprising in some ways, as it was expected that over such a
distance, scintillation would have been rather severe.
Why did the signals seemed to be minimally
affected by scintillation? While the air seemed
fairly clear, one can see from the pictures that there seemed to be a
small amount of particulate haze along the entire path.
The current theory as to why this would have an effect is that the
particulates in the air - in addition to causing attenuation - seemed
have resulted in very mild scattering of the beam all along the path,
the light from achieving a significant degree of "local coherence" - a
phenomenon described more than a century ago by A.A. Michelson.
This effect of "local coherence"
is imposed on even noncoherent light sources - provided that such a
light source is of very
small angular size. It is theorized that this "de-cohering"
effect caused by the dust particles all along the path and it seems to
be somewhat analogous to
the use of a de-cohering
screen described in the works of Korotkova.
This was not the first time that we'd observed the apparent effects of
airborne particulates on scintillation over an optical path:
Another such occasion was the first
attempt at the 107 mile path
which the path was severely obscured by smoke particles, resulting in a
barely-usable voice communications link. On that occasion, too,
it was noted that scintillation was extremely low - a contrast to the
same path in clear air a
few weeks later
in which scintillation was
Using the Spectran
the average signal-to-noise ratio of the 1 kHz tone was
analyzed - a task made somewhat easier by the very low amount of
scintillation and the use of long-term integration. Measurements
using several detection bandwidths was carried out, the results
"normalized" to 2 Hz and averaged together.
- In the George-to-Swasey direction, the average S/N ratio in a 2
Hz bandwidth was about 25.4dB.
- In the Swasey-to-George direction, the average S/N ratio in a 2
Hz bandwidth was about 19.6 dB.
- The average difference in signal/noise ratio is about 5.8dB -
favoring the southbound - the George Peak to Swasey Peak direction.
Of the 5.8 dB difference between the signals, I had previously
determined that the optical flux output of the transmitter used at the
north end (George Peak) measured 2.3dB higher in audio recovery than
transmitter. Assuming that the "background noise" (that is, the
additional noise attributed to extraneous light sources) is equal in
both directions, this implied that there was a receiver sensitivity
of about 3.5 dB at the George Peak end.
If we extrapolate this to a 50 Hz bandwidth we get:
- George Peak to Swasey Peak (north to south): S/N of about
- Swasey Peak to George Peak (south to north): S/N of about
This "50 Hz" bandwidth is that is the oft-quoted operating bandwidth of
"gray matter DSP" (the brain) in the presence of white noise and,
without filtering, it gives us an idea as to how much signal is present
to be able to dig weak Morse out noisy audio.
If another extrapolation is made to a 2 kHz speech bandwidth (300 Hz to
2300 Hz) and if
we assume that the psychoacoustic effects on intelligibility by inband
noise across this
bandwidth are "flat" (something that is not
- In the George Peak to Swasey Peak direction (north to south) the
2 kHz S/N ratio is about -4.6 dB. This resulted in "barely"
copyable speech to the trained ear when wearing headphones, but was
fairly easy MCW copy
- In the Swasey Peak to George Peak direction (south to north) the
2 kHz S/N ratio is about -10.4 dB. This resulted in "barely"
detectable speech and MCW copy was possible - but difficult.
Actual SSTV images
received at Swasey Peak via the 173 mile optical path, along with the
original images for comparison.
Click on the image for a larger version.
One experiment conducted was to send SSTV (Slow Scan TeleVision)
images. To minimize complexity and the amount of gear needed,
several images were generated prior to the trip and recorded as audio
files to be played back on-site: Decoding of the SSTV images was
to occur later via playback of the recorded audio files.
Because the signals in the south-to-north direction were weaker than
those in the north-to-south direction, SSTV signals were only sent from
George Peak to Swasey Peak. Using the MMSSTV program
were decoded from the recordings - but the low signal-noise ratio posed
a problem in decoding: The program would not reliably synchronize
to the noisy signals. Fortunately, MMSSTV includes a large
variety of selectable parameters that can be tweaked, making it
possible to render images from extremely weak and noisy signals and the
"knobs" were adjusted so that some semblance of an image was recovered.
As expected, the resulting images are barely recognizable
with the finer details having been obscured by both the noise and the
"smearing" caused by the tweaking MMSTV's filters - a necessary
trade-off to allow the processing of weak signals at all. When
SSTV experiments are done, an additional image will consist solely of
the callsign in very large, high-contrast lettering: I suspect
that had such an
image been transmitted it would have been readable, despite the weak,
noisy signals received.
Is should be noted that SSTV is not
a very efficient way convey information under poor-signal
conditions. If, for example, the
object was to simply convey a callsign across the link, any number of
other schemes (including Morse) would have been far more efficient and
reliable: The use of SSTV was mostly done out of curiosity.
As previously mentioned, one of the experiments attempted was to span
using a Laser mounted in the 8" reflector telescope. In the past,
this same gear was used very successfully over both 15 and 107 mile
paths: With the distant end centered in the eyepiece, the simple
substitution of the Laser emitter module required only minor tweaking
of the elevation to peak signals at the far end. On this
occasion, the audible S-meter was used in an attempt to detect
the Laser signal modulated with 1 kHz tone. While this has been
successfully used in the past, no tones were detected during the
attempts made this time. I decided to analyze the recordings
using Spectran to see if there was any hint of 1 kHz from the
Laser: None was observed. (Note: At the time, it
was locally verified that the Lasers were, in fact, modulated with a 1
Below are selected audio clips from the
One of the options of the
modulator is to generate a sequence of dissonant tones that are
designed to stand out in the noise, as the following clip demonstrates:
For the purposes of signal analysis, several periods of 1 kHz
tone were transmitted:
After acquisition of the signals, several MCW (Morse) exchanges
were made, one of which follows:
Signals from Swasey, received at George Peak, were somewhat
weaker, as the following clip demonstrates.
After the MCW exchange, voice was attempted in both
directions. The following clip contains the voice transmitted
from George to Swasey Peak:
More audio clips:
- Note: The following clips are in stereo
channel containing the audio received at Swasey Peak from
George Peak and the right
channel containing audio received, via backscatter, from the local
transmitter at George Peak.
- To hear only the audio
received at Swasey, listen to just the left
- The right channel (containing the backscatter)
included so that the listener may do an A/B comparison and determine
what is being transmitted.
- These recordings are composited by
having synchronized the digital recordings made at each end and making
a 2-channel audio file.
- You may have to use the balance control in the playback
program or the sound card's mixer to completely mute the undesired
Notes about the above audio clips:
- The theme from Dark Star.
(MP3, 0:30, 353 kB) Note that the use of
short duration (<30 second or
considered to be acceptable fair use under
current interpretations of
U.S. Copyright law. (Music: Theme song of the movie
Star by John Carpenter)
- VK7-Land audio exchange.
(MP3, 0:20, 241 kB) On 19 February, 2005, Chris Long and
Mike Groth spanned over 104 miles using an optical link. This is
a recording from that event that was played over the 173 mile optical
- SSTV Image #3. (MP3,
of several SSTV images that was
transmitted over the 173 mile optical link.
- Music Clip. (MP3,
kB) This particular music clip has been
used during each of our experiments, so it seemed fitting to use it
here, too. Note that the use of short duration (<30 second
considered to be acceptable fair use under
current interpretations of
U.S. Copyright law. (Music: "Children" [Dream
Version] from the album "Dreamland" by Robert Miles)
- Use headphones: It is strongly
recommended that headphones be used
when listening to the audio clips.
- Compression losses: Due to MP3 compression, some
of the finer details may be lost
and/or obscured by noise and artifacts. If you are really
interested, un-compressed .WAV versions are available.
- You may not be able to hear anything at all: It
may take an experienced "ear" to copy the weak Morse
signals amongst the noise. If you have had experience with
copying very weak and noisy signals - as is the case for amateur radio
operators who operate using such modes - you will more-easily be able
to make out the Morse code and voice present in these clips.
- There is some slight local voice pickup via the optical
receiver: The optical receivers are slightly microphonic, so
occasionally possible to hear the low-frequency components voices in
the background of those present
at the receive site or sounds from the radio's speakers. This is
most noticeable in first few seconds of the "Tone Sequence" audio clip
where we can hear a bit of the voice as people talk excitedly upon
hearing the tone.
- Rhythmic thumps: In some of the clips (such as
the "unfiltered" version of "Voice from George Peak") you can hear some
"thumps" in the background. These are from the strobes of distant
aircraft that are off-axis - but still getting a small amount of their
light into the receiver.
First of all, I'd like to thank those that
"Team Swasey" who had to backpack to the south site, carrying all of
the needed gear:
- Ron, K7RJ
- Gordon, K7HFV
- Brett, N7KG
- Tom, W7ETR, who went along on the first trip, but was unable to
the second trip owing to a schedule conflict.
"Team George" - who drove to the site:
- Clint, KA7OEI, who went solo on the second trip.
- Elaine, N7BDZ, who, like Tom, was unable to make the second trip
owing to a schedule conflict.
- Also present on the first trip, for moral support, were Paul,
Paul's son Scott, KE7OMB and Scott's son Brady, KE7OMC.
And, of course, Chris, VK3AML and Mike, VK7MJ and the others in
VK-land who provided continuing inspiration.
Swasey Peak: Ron K7RJ, Gordon K7HFV, Brett N7KG and
At the south end of the QSO on October 3, 2007:
George Peak: Clint KA7OEI and Elaine N7BDZ
- Ron, K7RJ
- Gordon, K7HFV
- Brett, N7KG
A ridge, about 0.22 miles (350 meters)
northwest of and 270 feet (83 meters) lower than Swasey Peak in the
House Range in Utah, approximately 40 miles (64 km) west of Delta.
39° 23' 25.1" N, 113° 19' 10.2" W
Elevation according to GPS:
9394 Feet ASL (2864
At the north end of the QSO on October 3, 2007:
On the ridgeline about 1.8 miles (2.9 km)
of George Peak, in the Raft River Range, just south of the the Idaho
border in northwestern Utah.
41° 53' 42.36" N 113° 26' 53.52" W
Elevation according to GPS:
9396 Feet (2865 meters)
The calculated distance (as a crow flies) as calculated
using the RadioMobile program, version 8.0.5 is 173.1 miles (278.6 km).
Note: There are several different methods used to
distance between two points on the earth's surface. The exact
calculated distance may vary slightly, depending on the
precision of calculation, the nature of the Earth model used, whether
or not the true elevation of the two points above sea level was taken
into account, and
exactly how the distance between the two points is assumed to be
spanned by the lightbeam.
Other path statistics:
Equipment common to both sides of the QSO:
- North-to-South azimuth: 177.7 degrees, true North reference.
- Minimum distance above ground in mid-path: 110 feet (34
meters) assuming no atmospheric refraction and a spherical
earth model. Due to atmospheric refraction, the "height"
the beam above the Earth's surface would have been greater than
this. This calculation assumes that the elevation of
both sites were the same which, in this case, is pretty close to being
Notes about audio recordings:
- The LED was amplitude modulated with a current-linear modulator
with a resting current of 1.1 amps. Details of the
modulator are here: LED_linear_modulator.html
- The transmit LED in both cases was a Red Luxeon III emitter
module (Lumileds M/N: LXHL-PD09) epoxied to a heat sink.
- The optical receivers were my "version 3" design, described
with both receivers using BPW34 photodiodes.
- Audio interface units, incorporating audio amplifiers, audio
recorder interface, audible S-meter, and a few other features were used
- details are here: optical_comm_audio_interface_device.html
- Both transceivers have separate and identical TX and RX lenses
Optical transceiver used on the South-to-North
link (at the Swasey Peak end):
- The "direct" recording: At each end, identical
digital, stereo digital audio recorders
were used to record both the transmitted audio (left channel) and audio
from the receiver (right channel.) For these events, a rate of
32000 samples/sec was used with the audio recorded in uncompressed 16
bit .WAV format. The audio recorders (Insignia NS-DV4G) have well
70dB S/N ratio and 4GB of recording capacity, allowing many hours of
sample-accurate recording. Because identical-model recorders were
used, the sample rates were extremely close, greatly simplifying the
synchronization of the two recordings. These recordings allowed
both the receive and
transmitted audio to be analyzed in detail to for later analysis and
timeline of events. Uncompressed
signals: Any lossy audio compression would probably obscure finer
- The "open-mic" recording: Another invaluable piece
of data is an "Open-Mic"
recording. For this, an inexpensive digital audio recorder with a
microphone is placed near the operators (but not too close to the
speaker of either the radios or optical receivers) to pick up the
operators' comments and radio traffic. This is useful tool
in being able to determine the timeline of events, plus catch
contemporaneous thoughts and impression that would likely not be
remembered later. Unfortunately,
mic" recorder, but since I was alone there
was no dialog with anyone else onsite and it would have
captured only transmissions made via radio or the optical transmitter -
both of which were caught jointly on the "Open-Mic" recording made at
Swasey as well as my own "direct" recording.
Optical transceiver used on the North-to-South
link (at the George Peak end):
- This enclosure is described in detail here: Optical_enclosure_first_version.html
- Lens size: Unmounted, the Fresnel Lenses are 250mm x 318mm
and have a focal length of 318mm. The mounting frames vignette
the lenses by about 10mm in each dimension, so the available lens area
is about 240mm x 308mm. Each lens is protected by a sheet of
Plexiglas and the front surface has been coated with a protective
polymer to prevent scratching and moisture accumulation.
- For optimal far-field optical flux density, a glass PCX
(Plano-ConveX) lens is used in front of the LED to appropriately
illuminate the Fresnel, the LED-Lens distance being set empirically for
A timeline of events:
The times in bold are UTC, 3 and 4 October, 2007
while those in parenthesis are local time, MDT, mostly 3
October. The timings of events are from recollections, GPS logs,
and the audio recordings.
- The enclosure is described
- Lens size: Unmounted, the Fresnel lenses are 404mm x 430mm
and have a focal length of 229 mm. The mounting frames vignette
the lens by about 10mm in each dimension, so the available lens area is
about 394mm x 420mm. Each lens is protected by a sheet of
Plexiglas and the front surface has been coated with a protective
polymer to prevent scratching and moisture accumulation.
- For optimal far-field optical flux density, an acrylic
DCX (Double-ConveX) lens was reground to an aspherical shape to provide
optimal illumination of the Fresnel - a step that turned out to be
necessary owing to the very short focal length making it
difficult to efficiently illuminate the lens. This LED/Lens
combination produced about 23% higher far-field flux than
transceiver used at Swasey Peak.
1600 (1000) Team George
(Clint) departs Salt Lake
1830 (1230) Team George
departs Standrod to climb mountain
1939 (1339) Team George
gets stuck in the snow
2000 (1400) Team Swasey
starts the ascent
2111 (1511) Team George
finally gets out of the snowbank
2215 (1615) Team George
arrives onsite - start setup
2245 (1645) Team Swasey
arrives at the selected spot: Starts out on an exploration trip
2320 (1720) Team Swasey
explores the summit, tries to signal via mirror
0120 (1900) Approximate
time of sunset at both sites
0145 (1945) It is finally
dark enough to have a reasonable chance of seeing beams from both ends
(2048) Possible spotting of the beam at
Swasey via telescope: Beam alignment/peaking begins
0308 (2108) First
vestiges of signal heard with
the electronic detector
First keying of Swasey to attempt being heard at George
First "via ear" copy of tones
MCW (Morse) exchange begins
MCW acknowledgment from Swasey: 2-way exchange complete!
Brett finally spots the light from George Peak
Start of 2-way voice exchange
End of 2-way voice exchange
Attempt begins to aim telescope-mounted Laser toward Swasey Peak
Attempt begins to aim Laser pointer at George Peak
to the KA7OEI Optical communications Index page.
Laser signal acquisition attempts ended
Begin playing of the theme song from the movie, Dark Star
Playback of VK Audio clip across link
Begin of SSTV playback
Began playback of excerpt of music clip ("Children" by Robert Miles)
Testing completed - everyone starts to pack up and go home
0513 (2313) Team George
departs the mountaintop
1215 (0615) Approximate
time at which both teams arrive home.
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