Click on any picture for a larger view
The Medicine Butte
Repeater
Part of the Intermountain
Intertie
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About Medicine Butte:
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Medicine Butte is located about 5 miles northeast of Evanston, Wyoming. While the Butte itself is nearly 2000 feet higher than Evanston, the radio site for the 146.86 repeater is several hundred feet below the top. With this site being down the south side of the hill, coverage to the north is severely restricted. Coverage into Evanston is very good, however, extending along I-80 as far west as Wahsatch (yes, that is how it is spelled...) and as far east as Little America. Toward the south, it provides good coverage of the northern slopes of the High Uintas. It is worth mentioning that this is not the only amateur repeater on Medicine Butte: Consult repeater listings for more information on these other systems.
The Site:
The building in which the repeater is located
is primarily a TV
translator
site. Several of the Salt Lake TV stations are received at
this
site
and are relayed into Evanston and/or into other rural areas of
Utah and
Wyoming.
The actual site
"owner" is another ham - Pat, AD7V who lives in
Manila,
Utah. It is through this site that many of the off-air
TV
stations
are relayed to get to some of the outlying areas in Eastern
Utah.
Getting direct feeds from Salt Lake is severely complicated
due to the
fact that the Uinta and Wasatch mountain ranges - both of
which easily
exceed 11,000 feet - are in the way. This site provides
a way
"around"
the north and eastern end of the Uinta range - which is
somewhat
unusual
in that it runs East-West as opposed to the more typical
North-South.
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Like any mountaintop site, getting commercial
power is somewhat
awkward.
Fortunately, Medicine Butte isn't a particularly tall mountain -
and it
isn't all that far away from the city of Evanston either.
Nevertheless,
the commercial power arrives via a fairly long run on overhead
lines.
Being at the end of the line, one can typically expect all sort
of
voltage
variations and line transients - but taking appropriate measures
(isolation
transformers, rugged power supplies, etc.) can minimize any
potential
problems.
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If you are familiar with the GE Mastr (and Exec) II radios, you may also be aware of a potential "problem" with these radios. This problem manifests itself by a gradual or sudden receiver "deafness." This problem can often be "fixed" simply by smacking the receiver - but the problem will generally return. The problem is one of metallurgy: The front end filters of the receivers are made of pot metal which is plated with something else (tin, perhaps?) to which the coils may be easily soldered. Some production runs of this radio exhibit an interesting problem: Extremely fine dendrites (e.g. metallic "hair") will grow from the walls of the casting and eventually short out the coils inside. These dendrites are extremely fine - invisible unless you have extremely sharp eyes or a microscope. If you jar the radio, you can often break enough of these off to restore sensitivity - but they will grow back. These dendrites can form in radios mounted in cars, too - but when they do form in these radios, they tend to be quite rugged and nearly immune to being broken due to jarring. This phenomenon is likely a result of a reaction between the plating, the pot metal in the casting, and oxygen in the atmosphere (but no-one seems to know for certain.) Because these radios are remote and inaccessible for months at a time, it is in our best interest to prevent this from occurring. Not all GE Mastr (and Exec) II's are susceptible - but one way to tell if your radio is to run your finger along a smooth surface of the front-end casting: Even if it "looks" smooth (often it won't - it will look as though it has a bit dust on the surface -which will rub off if you draw your finger across it) but feels somewhat "bumpy" or "sandy" - you are in trouble: The radio may work at the moment, but it will likely go deaf in the future. Here is what to do:
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Interestingly enough, one thing to avoid using in mountaintop locations such as this are MOV-type surge suppressors. The problem with MOVs is that, upon repeated "firings" (due to frequent line transients, etc.) they tend to degrade - and when they fail, the often fail shorted. This will, of course, short out the circuit and take the equipment completely off line, requiring a site visit. If you are interested in avoiding downtime as well as preventing damage due to transients, simply having an isolation transformer (or better yet, a ferroresonant transformer such as a "Sola" [tm]) will take care of about anything that would have caused you damage in the first place. Another good device to have in line is a simple, old-fashioned "brute-force" AC line filter. These will, by their very nature, take out most of the line transients that come along simply because they are low-pass filters - and power line spikes are typically "fast" (e.g. high frequency content) events. Finally, old-fashioned transformer-type linear supplies tend to have much better longevity (and be quieter - in terms of RF) than most of the newer switching-type supplies.
The Repeater:
The repeater itself consists of a GE Mastr II mobile modified for repeater operation and the controller is a LinkComm RLC-4 that is connected to two UHF link radios: These radios (which are also modified GE Mastr II mobiles) are used to tie this site to the Intermountain Intertie via the Hidden Peak hub (at the top of the Snowbird tram) and to the Aspen Mountain repeater (146.67) southeast of Rock Springs, Wyoming, connecting it to the intertie as well. This site's linking into the Intermountain Intertie effectively ties the southwestern corner of Wyoming in with most of the state of Utah, parts of Idaho, and into parts of northwestern Arizona and southern Nevada.
As you can see from the picture below there are really two structures being used on Medicine Butte. The larger building (the camouflage structure visible in the panoramic view) not only houses the amateur equipment, but it has a number of television and FM translators that serve Evanston, Wyoming and the communities around Manila, Utah (near Flaming Gorge Reservoir.)
The smaller building (formerly used to house the translators) is used to support the amateur antenna structures. A section of heavy pipe is used to support a the 2 meter repeater antenna (a pair of phased folded dipoles) as well as two small yagis - one pointed toward the Hidden Peak hub at the top of the Snowbird tram, and the other pointed toward the Green River/Rock Springs area. A messenger cable carries the coaxial cables overhead, connecting the two buildings.
Additional Pictures from a more recent trip:
On August 3, 2002, John (K7JL) and Larry (KB7YAF) visited the Medicine Butte site. This site is at least a 2 hour drive from John's Salt Lake area QTH - so even a short trip will kill at least half a day.
The reason for the trip was to investigate noise that had appeared on one of the receiver links, probably the link from Green River/Rock Springs. There also appeared to be an intermittent problem with a UHF transmitter, too.
True to Murphy's Law, the noise problem never appeared when they were on-site. Some modules on the UHF transmitter were replaced, however - apparently fixing the intermittent problem.
Of course, the noise reappeared a few days
later, but this was taken
care of (temporarily) by turning off the receiver on the Green
River/Rock
Springs link. Because the far end of that link is down at
the
moment
anyway, there isn't much of a problem with having it turned
off.
Another trip is tentatively scheduled to take care of the
problem.
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Careful observers will note that the antenna shown above is not the same antenna shown in the picture at the top of the page or in the panoramic view at the bottom. That antenna (a Maxrad 1403) suffered the fate that seems to befall this particular model of antenna: The top whip disappeared - probably breakage due to metal fatigue.
This antenna was replaced with the pair of
phased dipoles that you
see
in the above picture in late 2001. These dipoles are
side-mounted,
adjusted so that they put a null in a northeast direction.
Why do
this? Because this side is not on top of
the
mountain
- but down the side some distance - it is blocked in this
direction,
hence
there is no need to radiate signal in that direction.
Side-mounting
the antenna in this manner not only puts a null in the direction
of the
blockage, but it increases the amount of signal radiated in
other
directions,
as well as reduces the pick up of interference that might
originate
from
the other site.
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Finally, the folded dipoles are inherently DC grounded. This tends to reduce the tendency toward static discharge and, in the event of a lightning strike, will tend to shunt more energy into the ground system - hopefully minimizing damage.
The other picture shows the building containing the TV translators and repeater. Three "paraflector" [tm] antennas may be seen in the picture and these are used to beam the translated UHF TV signals closer to their destination. Atop the pole is yet another TV antenna (not visible in the picture) used to beam signals into Evanston, Wyoming. Along the right side of the picture may be seen the messenger cable used to carry the coax cables to the "antenna building."
Typically, these types of TV translators run very low power: Often, as low as 1 watt is used - but rarely more than 100 watts. Such low power is possible because fairly directional, high-gain antennas are typically used on transmit as well as receive. In other words, people served by translators in rural areas can rarely get away with simple rabbit-ear antennas: More typically, larger rooftop antennas are used for reception - either by the viewer, or by the cable company receiving the signal in the first place.
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This page was last updated
on 20121220