The Utah VHF Society

The Medicine Butte Repeater
Part of the Intermountain Intertie

The Medicine Butte Repeater:
  • Callsign:  K7JL/R
  • Output Frequency:  146.860 MHz
  • Input Frequency:  146.260 MHz
  • Subaudible Tone Frequency:  100 Hz
  • Location:  Medicine Butte (approx 5. miles Northeast of Evanston, Wyoming)
  • Coordinates:  41 deg 20' 49" N, 110 deg 54' 03" W (NAD27 Datum)  Grid Square DN41ni
  • Elevation:  Approx. 8400 Feet (2560 Meters)
  • Coverage:  Northeastern Utah, Southwestern Wyoming (about halfway to Rock Springs along I-80) 
  • Link Status:  Full-time linking to the Hidden Peak repeater (147.18) and the other repeaters served by the Intermountain Intertie.

About Medicine Butte:
A view of the Medicine Butte site looking south with the north slopes of the high Uintas being just visible in the background.  The two buildings and the multiple antennas may be clearly seen.
Click on any picture for a larger view

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.  
Norm (N7ZOI) checks the VSWR on the Rock Springs UHF link antenna.

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.
Avoiding "hair" in the GE radios...

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:

  • Completely remove the casting from the radio.
  • Remove all circuit boards and covers.  Make sure you note which screws and wires go where!
  • "Scrub" down the inside and outside walls of the casting with a cloth or paper towel.  If the coils are still installed, you will likely need to use a small screwdriver to get the cloth or towel around and behind the coils.  Do your best to rub down every single surface of the casting.  (On a lowband radio, it may be possible to remove the tuning capacitors/coils.)
  • If you have compressed air, blow a lot if it through and around the casting.  This will remove metal flakes and powder that you may have removed - as well as (hopefully) blown away any dendrites that you may have missed.  If you don't have compressed air, do the best you can with your own lungs.
  • Degrease the entire casting.  You can do this by rubbing it down with denatured alcohol-saturated rag, or by using a spray-type degreasing (non-residue - do NOT use "tuner" cleaner) solution.
  • After the degreaser has dried, spray 2 or 3 coats of clear lacquer over the entire casting, inside and out, allowing it to dry between each coat.  Don't be afraid to get it on the coils, but be sure to pour out any "puddles" that might form inside the casting.  Between coats, turn the tuning adjustments a bit to prevent "seizing."
  • When you re-assemble the casting, observe that some surfaces (such as circuit boards) require electrical contact with the casting - make sure that you scrape the lacquer off these surfaces to assure good electrical contact.
  • Of course, the receiver should be completely re-aligned.
This technique has proven to be successful (so far) - and none of the radios treated in this manner (as far back as 1998 at least) have yet to have "hair" problems.

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.
John, K7JL, standing next to
                    the antenna building at Medicine Butte
John, K7JL, standing next to the antenna building at Medicine Butte.  Two UHF yagis (one pointed toward Hidden Peak and another one pointed toward Green River/Rock Springs) may be seen.  The 2 meter repeater antenna consists of the two side-mounted folded dipoles.
Click on the image for a larger picture.

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.
A view of the repeater
                    building itself, showing some of the TV translator
This is a view of the actual building containing the repeater and TV translators.  Some of the UHF reflector-type antennas may be seen beaming their signals toward northeastern Utah.
Click on the picture for a larger version.

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.

For a really
W  i  d  e   A  n  g  l  e

360 degree panorama from the near the 146.86 Medicine Butte repeater site.  The center of the picture is toward the south-southwest.  This view shows Norm (N7ZOI - on the roof) and Larry (KB7YAF - on the ground) working on the antennas.
For a BIG picture, click on the image above.  WARNING:  It is 5710 x 469 pixels and over 200k in size!

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This page was last updated on 20121220