Panoramic view to the north, showing the 02/62 repeater's receive
site (center.)
For a wider view, click here.
Panoramic view to the north, showing the 02/62 repeater's receive
site (center.)
For a wider view, click here.
A Visual tour of the repeater
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Because of its location, Farnsworth Peak is one of the best transmitting and receiving sites along the Wasatch Front. The north end of the range has a clear view in that direction, to the west, and south into Utah county. Because of this it is heavily used for transmitting radio, television, and other telecommunications. In fact, the Farnsworth peaks have most of the Salt Lake FM broadcast stations, many of the television stations, and many paging systems.
Being such a good transmitting site is not without its problems. The multitude of transmitters on a myriad of frequencies has caused the noise floor of the site to increase, thereby reducing the possible maximum sensitivity of a receiver on-site, especially at VHF.
Because of this, when the site was surveyed for repeater use it was noted that down the mountain some distance (about 400 feet) the distance provided enough isolation to nearly eliminate the noise floor. A remote receive site was thus established.
Shown is the receive site, its tower, and antennas. The black antenna (on the right) is the main receive antenna. It is placed on the tower to provide a null toward the transmitter site to reduce the possibility of interference from the transmitter site. At the top of the tower is a simple J-Pole antenna - to be used as a spare, should the main antenna be rendered unusable for some reason. (Note: The "spare" antenna has been used as the "main" antenna for the past several years due to the fact that, for some reason, it seems to work slightly better than the "main" one.)
It might have occurred to the reader that the '62 repeater is different
from "most" repeaters that one runs across: The Transmitter and Receiver
are in different locations! Normally, both the transmitter and receiver
share not only the same antenna, but the same feedline, duplexer, and cabinet.
While that could have been done in this case, the intrinsic noise level
of this site would make receive performance suffer. For this reason,
the receiver is located some 400 feet north of the complex, down the hill
some distance. See "A Brief History of the '62 Repeater" below
for more details.
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One thing that every repeater needs (in order to be legal, at least)
is a means of controlling it. This could be something as simple as a switch
(if the repeater is, say, located at someone's house or some other location
that is staffed continuously) or a telephone line that allows remote control.
One of the most popular ways to provide repeater control, though, is with
control receiver. FCC rules clearly state that control of a repeater
may be done only on the 222 MHz band and above. The '62 repeater
complies with this rule by having not only a switch that can be flipped
(it turns out that Farnsworth Peak is staffed all of the time anyway)
but it has a 222 MHz control receiver.
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The repeater controller provides functions such as the timeout timer, the ID and its timer, audio switching and squelch control, as well as decoding the control sequences received on the control receiver. One of the unique features of the '62 repeater is the ability to remotely set the squelch of the receiver - a big improvement over having to drive up there just to turn a knob, or trying to convince one of the already busy staff members up there to do it for you.
The audio and keying line from the controller go first to the exciter ("Exciter" is just a fancy word for "low power transmitter", in case you were wondering...) The exciter generates the 146.62 transmit signal and modulates the audio on it. Its output power is just a watt or so, so there is a 100 watt power amplifier that is used to bring the power up to a more respectable level. With the antennas being used, this 100 watt level is just about right to allow the the repeater to be heard as well as it can hear.
To have too much power would make the repeater an "alligator " (all mouth and no ears) while running too little power would make it an "elephant" (ears too big...) Either situation in an extreme make the repeater less pleasant to use: Too few people can get into an "alligator" repeater and too few people can reliably hear a repeater that is an "elephant." Clearly, if one has to choose between an "alligator" or an "elephant" one should always pick the "elephant" situation: It is more common to have people who have trouble getting into a repeater than hearing it!
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If Farnsworth Peak is anything, it is busy - at least RF-wise. It is host to, by far, the largest concentration of broadcasters in the state. This means that there is a tremendous amount of energy floating around in the air. Ironically, even though it is a great site for transmitting, it is a terrible site for receiving - at least on 2 meters. It is because of this that the receive site is remotely located. (See the pictures above, and the history, below.) To keep ourselves in good graces with the landlord, as well as to protect our own equipment and to radiate a clean signal, the transmitter has several cavities on its output. These cavities act as very narrow filters to pass only the transmit frequency.
There is also an isolator just before the cavities. This device
allows the transmitter's power to flow from the transmitter to the
antenna feedline, but any power that comes back (such as that resulting
from an SWR or other transmitters on other frequencies being picked up
by the transmit antenna) are sent into a dummy load. This keeps the transmitter
from every seeing a bad load - which might happen if the antenna were to
ice over or get damaged - and being damaged by too much reflected power.
It also keeps the signals from other transmitters from getting into the
power amplifier and causing spurious signals from being created.
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The transmit antenna used by the '62 repeater is nothing fancy:
It is just a J-Pole. While it is quite common to use a much larger
antenna on repeaters, this location on the mountaintop has its own set
of complications: There are times when the sustained windspeeds
exceed 100 MPH (160 KPH) and a large antenna proves to be a liability rather
than an asset: Not only does a larger antenna "catch" a lot more
wind - something that puts strain on the tower and its supports - but such
a large antenna is an expensive item - with a rather short lifetime.
The small, humble J-Pole doesn't catch a lot of wind, it is fairly
strong if made from 3/4" pipe, it isn't as much target for demolition by
flying chunks of ice, and it is cheap! It's low gain is made up by
the use of the 100+ watt amplifier...
The idea of a repeater on Farnsworth Peak began to emerge shortly after UARC's success in putting the 146.76 repeater on the air in the mid 70's. Some hams who had had experience in the television industry called Farnsworth "the best site in the state of Utah." The 9000-foot mountain sits near the north end of the Oquirrh range which is just west of the Salt Lake valley. It certainly appeared that it had a wonderful view of the valley and a chance of getting into Logan.
One sour note kept coming out, however. There were reports that the site had bad noise and intermodulation problems. So a party was assembled to go to the mountain and check it out. Permission was obtained from KSL-TV, owners of the site, to make a visit, and a spectrum analyzer was obtained. The party headed for the 9000-foot level.
They found that the reports of receiving problems, unfortunately, had been correct. As well as big spikes that the analyzer showed popping up randomly from intermodulation products, it showed a lot of "grass," a low level noise floor that would surely mask any weak signals. On the positive side, the view from the site certainly looked promising. The whole Salt Lake valley was laid out before us; most of Utah valley was easily visible; we could look straight into Grantsville; and the view to the northwest, across the Great Salt Lake toward Idaho, seemed to go on forever before disappearing in the haze.
In the months that followed, a partial solution appeared when one of the local hams offered access to nearby Kessler Peak, just north of Farnsworth. Although not quite as high as Farnsworth, this peak had no television station and probably did not suffer from the noise problem. It had its own set of disadvantages, though. Space was severely limited, so only a small antenna could be accommodated. Management concerns were such that we would be able to access the site only when the ham that worked there was available.
We thought a hybrid arrangement could be devised. Why not put the transmitter for the new repeater and its logic on Farnsworth, and put the receiver on Kessler? We could take advantage of the lower noise level on Kessler and the greater accessibility of Farnsworth at the same time. The rough spot here was that some sort of link would have to be built to send the receiver audio from Kessler to Farnsworth.
We started procuring equipment for the new repeater, keeping in mind that transmitter and receiver might be separated in the final configuration. About this time, Dirk Ostermiller, W7KCC, the club's repeater engineer, who had spearheaded the '76 project, found that his time was overcommitted. He resigned and left the Farnsworth project to others to complete.
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Randy Finch, K7SL, agreed to take the position, and started assembling the new equipment into a working repeater. Before long, a new 146.61 MHz repeater appeared on the air from Randy's home in Magna. It came on just in time to be announced at the 1979 UARC Christmas Banquet. (The switch to 146.62 came a few years later when Utah adopted 20 kHz spacing, the plan pioneered by Washington and Oregon.)
By the time we got that far, another monkey wrench seemed to have fallen in the works. (We thought we could blame it on Murphy, but it wasn't even close to Field Day.) Other commercial installations had consumed most of the remaining space at the Kessler site, and it was no longer available to us.
After some amount of hair-tearing and carpet-pacing, the idea of a split site at Farnsworth was born. We contacted people at KSL to see if they would go along with the idea of letting us just plop our receiver outdoors somewhere away from the building (and the noise). They told us their property ended on the south just a short distance from the TV buildings, but it extended quite some distance to the north, and something north of the building might just work out.
It would have cost us too much to do Class 1 wiring to bring power down to the remote site. So placing the entire repeater there was not practical. But just a receiver could run happily on 12V at 100 ma. So a split-site repeater seemed to be the answer.
Summers are short at 9000 feet. Usually, by June, it is possible to clear the remaining snow from the road and declare the road open for travel. Snow often closes it again by October. We waited impatiently for June of 1980 and clear roads to come along. Finally the time came. Randy and the author went to the mountain taking a mobile 2-meter rig, a Gel-Cell, a 1/4-wave whip, and a cavity. We hooked it all up just north of the TV station buildings. Sure enough, an S-9 noise level.
Next, we started walking down the ridge to the north, away from the buildings. The S-meter started to drop, just as we had hoped. It finally reached a zero reading about 400 feet north of KSL's northernmost building, the tram shack. We ceremoniously announced, “The receiver goes here!”
Of course, declaring it so and making it happen were two different things. Many man-hours from a large number of volunteers were required to finally place a repeater on the mountain. Steve Kleinlein, WC7G, built a power supply. Larry Jacobs, WA7ZBO, built two J-pole antennas. Russ Michaelson, N7SM, built rack-mounts for several pieces of equipment. Steve Berlin, WB7VCI, built the audio board for the controller. Don Richardson, WA7QKF, built the logic board. Mac MacDonald, WA7SVN, built an ID board. Randy built many of the remaining pieces and coordinated numerous work parties on the mountain and in his basement.
Work continued. Copper for a ground system was obtained. Burial cable that could be used to connect the transmitter site to the receiver site was located. A rack was found to use for the transmitter end of the repeater.
A space was negotiated with the KSL staff for the transmitter. It was
in a dark corner on the upper level of the old tram building. The brake-release
arm was conveniently located where one could sit on it to work on the repeater.
Only a thin layer of metal separated us from the elements outside, and
this metal had a number of holes in it. We would have to provide some rain
and snow protection for our rack. A plastic cooler cover finally met this
need.
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As bizzarre as this space was in some ways, it had some features that made it just what we needed. It was at the end of the KSL buildings closest to our chosen receiver site, and it was not likely that any commercial clients would be competing with us for it.
The solution to one problem fell into our laps unexpectedly. A gentleman had donated an old commercial repeater to the club. He had planned to use it at a particularly good mountain site. Before he got his repeater on the air, however, his work took him out of the country for several years. When he returned, he found that someone had already put a repeater on at the Snowbird ski resort, so he donated his equipment to UARC. It was old tube gear and the receiver did not have a particularly good reputation, so we thanked him kindly and put the unit in storage.
But as the contruction of the Farnsworth repeater proceeded we remembered one very useful feature of the donated repeater: it had a weatherproof rack! Soon a worthy receipient for the transmitter and receiver strips was found and their rack became the new home of the Farnsworth receiver.
How time flies when you're having fun! There was snow on the ground at Farnsworth again by the time we were ready to erect a tower for the remote receiver. It took several weekend trips to get a hole dug, and about 15 hams to actually erect the tower. We had to carry up, not only the cement, sand, and gravel, but also the water. The final fifty feet of the journey was uphill and had to be done on foot.
A few more weekends were devoted to burying the cable that would connect the two sites. It was a multi-pair cable and the design called for one pair to carry 12-volt power down to the receiver, another to bring audio back up, and a third to bring squelch information up. It sounded easy enough to dig a trench, but most of the ground turned out to be not soil, but stones on top of bedrock. We settled, frequently, for just piling rocks on top of the cable.
Other trips were made to get equipment up to the mountain. On one of these a great clatter arose as the vehicle pulled out from in front of Randy's house in Magna. It seems that the exciter and receiver had been placed, temporarily, on the roof of the the Jeep while it was being loaded. Somehow, they never got moved to more permanent storage, and were thrown out on the asphalt as the Jeep started to move.
Perhaps dropping the RF gear on the road is a necessary part of the initiation of UARC repeaters. Several years earlier, the '76 repeater had been carried to its site in a truck supplied by the National Guard. Part way up the 30% grades, the whole rack fell out.
The moment of truth for the Farnsworth project finally came on a Saturday
night in the fall of 1980 when two different teams worked at hooking up
the cables at the transmitter and receiver sites. The power and squelch
pairs had to be connected with correct polarity, but no particular color
standard had been agreed to by the two ends. We figured we would just hook
it up any old way, take some voltmeter readings, and then reverse whichever
pairs were wrong. The crew at the receiver end was ready first, but couldn't
do much until the transmitter crew fed them some power down the cable.
So they waited impatiently, making occasional wisecracks on simplex. Finally,
the transmitter team got ready to call on '61 simplex and announce that
power was on. They never got the chance to make the call.
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Suddenly, the repeater was on the air, and there was a station using it from Snowville, Utah, near the Idaho border. Magically, the right polarities had been found on the first try. Why someone in Snowville happened to be trying the 01/61 repeater pair at that moment is still mysterious. But, the repeater was on the air! It wasn't the best-sounding repeater in the world. In fact, its audio was troubled by mysterious hums, squeals, and bursts of audio from the FM broadcast stations on the site. But after another hour of cable routing, bypassing, and level adjustment, it began to sound like a useable repeater.
It's very traditional for new repeaters not to make it through their first night. This one survived its first night, but its first day was a different story. When things came up to daytime temperatures, it became clear that the squelch was too loose, and the repeater was transmitting noise for long periods. The author and Scott Bidstrup, WA7UZO, made a trip and cured the problem.
After that, the repeater ran happily through the winter. Useage was light, but gradually, a few people began using the machine. We thought our job was done.
The real excitement didn't start until late spring when the first thunderstorm came by and the repeater promptly went off the air. We went to the mountain and repaired some power supply components and added some surge supression. The next week another storm came by and the repeater was off again. We went to the mountain and replaced some cable-receiver components and added more surge protection.
Soon, it became the joke that '61 was a better weather predictor than the Weather Service. It went off the air at the first hint of a storm coming in from the west. This seemed unfair, because, by this time, we had beefed up the circuitry to the point the repeater only went off every second or third thunderstorm. Sometimes it would be on for over two weeks at a stretch. However, some of the IC sockets were wearing out because the parts in them had been changed too many times.
Our problem seemed to revolve around the fact that a 10,000-amp lightning stroke parallel to our cable (the one connecting the transmitter site to the receiver site) could easily induce enough voltage to destroy the ICs at both ends. We finally realized we had to convert to a new religion and espouse a creed the phone company had known about for years: The way to minimize induced voltages in a balanced pair is to make sure there is no ground reference. The cable pairs would have to float and have no ground connection.
To practice our new belief, we had to make sure everything that went from one site to the other had to couple through transformers at both ends. That, in turn, meant everything had to be a-c. That was no problem for the audio -- it was a-c already. For the power, it meant we had to wind a couple of unusual transformers and feed the line with 60 Hz. The hardest one to convert was the squelch line which carried DC proportional to the receiver's noise detector voltage.
Just a little too sure of our abilities, we decided we could do the conversion one evening after work. I breadboarded an op-amp circuit to convert the squelch circuit's DC to a pulse-width modulated signal. Randy rounded up transformers and built a more permanent model of the circuit. We enlisted Dale Jarvis, WB7FID, and headed for the mountain. We didn't leave until daylight was in the east, a scheduling feature we had neglected to tell Dale about. The famous “modification 42” was complete.
The repeater was much more reliable, now, reaching a rating of 6 mtsbf (mean thunderstorms between failures). But it took modifications 43 and 44, involving huskier receiver and driver transistors, respectively, before it really settled down. Thus, by the end of 1981, the thuderstorm problem was pretty well behind us.
Some of the changes and enhancements over the years included:
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This page last updated on 20030218