Predicted signal strength contour map from the 146.62 Farnsworth Peak repeater.
Click on the image for a larger version.

One of the reasons that Scott's Hill was chosen for the site of the other repeater in this system is because of the minimal overlap between the coverages of the two sites.  Farnsworth Peak (in the Oquirrh range) covers very well to the north and west, but it does not cover to the east beyond the Salt Lake valley.  This is because the elevation of the Wasatch Range (the mountain range that is immediately to the east of the Salt Lake valley) can exceed that of the Oquirrh range by more than 2000 feet.

Conversely, since the Wasatch range rises abruptly (more than a mile...) above the valley floor it effectively blocks anything that is not on the "front range" from a view of the valley-  and Scott's Hill is definitely not on the front range.  It does, however, provide reasonably coverage to the east into Park City, Heber City, and other "high Wasatch" communities (as well as the high Uinta range) and to the northeast into southwestern Wyoming into Evanston and Kemmerer.

Although they would be "just predictions", it was decided to "run the numbers" to get an idea of just what sort of coverage and overlap one could expect from the two sites.  The program that was used to do this references an extensive terrain database and takes into account (within reason) the effects of that terrain on the signal.  It does not realistically predict some small "hot spots" or "dead spots" that may mysteriously appear in small areas, but it may be regarded as a general guideline of what to expect.

It has been noted that, technically speaking, these predictions would appear to be generally optimistic.  Theoretically, the weaker parts of the blue area (i.e. 20 dbuV/m) should yield a signal that presents approximately 2 uV to a receiver (using an isotropic antenna.)  Real-world experience shows that the "weak" blue areas have signal that are quite weak - even to a well-equipped mobile antenna.  For this reason, the third column in the signal strength table (i.e. the "actual signal quality observed..." column) should be trusted more than the straight field strength predictions.  It helps to consider the colors as being indicative of the probability of finding a useable signal path (hence, the last column.)
 

Table of colors used on maps to indicate signal strength

Map Color	Field Strength using a unity gain antenna	Typical signal quality observed during operation
RED	>63 dBm (>200 microvolts)	Strong signal, solid coverage, generally "HT"able.
YELLOW	Around -75 dBm (30 microvolts)	Generally good signals:  May "HT"able with a good antenna and in a good location, solid "50 watt mobile. coverage.
GREEN	Around -97 dBm (3 microvolts)	Reasonably good coverage with occasional "picket fencing" in a mobile.  HT operation possible with a good location if a "hot spot" is found.
CYAN	Around -107 dBm (about 1 microvolt)	Signals will be fairly spotty and weak even in a moble and may require a "hot spot."  Good coverage with a gain antenna from a fixed (home) location.
BLUE	Around -117 dBm (about 0.1 microvolt)	Signals in this area are extremely weak and spotty.  Coverage from a fixed (home) location using a good gain antenna (such as a yagi) may be possible.
(No color)	< -117 dBm (<0.1 microvolt)	Signals in these areas are extremely weak or nonexistant and coverage is unlikely.

 

Predicted signal strength contour map of the UARC Scotts Hill repeater.
Click on the image for a larger version.

A word about the maps:

As was mentioned above, the program generates signal strength predictions based on an extensive terrain database.  This program outputs a signal strength map that has only latitude and longitude grid lines on it with no references to cities, roads, or mountains (see below for links to these original maps.)  The lack of detail makes these maps difficult to use.

In order that this information be made more useful, these maps were overlaid atop a relief map such that the colors from the signal strength map show up but the relief data is still visible through it.  The result of this effort may be seen on the three maps on this page.

Clicking on any of these three maps will download a full-sized version.  You should be warned that these maps are approximately 225 kilobytes in size with dimensions in excess of 1100 pixels square!  If you wish to print these maps on your color printer, you may not be able to do it from your browser:  that is, you may just get one corner of the map on your page.  You may have to save these images to disk and then use a program that will scale the image to fit the page on your printer.

The table shows which color correspond with a given range of signal strengths.  You should be careful, however, to note that the "yellow-ish" color along the edges looks similar to the "brown/orange-ish" color near the center of the map (near the "green" areas.)  Familiarize yourself with the difference between the way those colors show up...

In both cases, the contours show the expected signal level with 100 watts ERP with the receive antenna at 20 feet above ground.  The transmit antennas are assumed to be 30 and 20 feet above the ground for Farnsworth and Scott's respectively.

Comparison with a "known" site:

For the purpose of comparison, the predicted contours for the Hidden Peak repeater (a.k.a. "Snowbird") may be found on the third map.  This site may make an interesting basis of comparison, as it is fairly close to Scott's Hill (geographically speaking) and it's coverage characteristics are well known, as this repeater has been at this location for nearly 30 years.  The differences in coverage are interesting and based on the fact that not only is Hidden Peak a bit farther south, but it is a bit more than 1000' higher in elevation (i.e. at 11000 feet.)  Like Scott's Hill, the ERP is assumed to be 100 watts from an omni antenna at 20 feet AGL.

Some observations based on these predictions:
 

Predicted signal strength contour map from the 147.18 Hidden Peak (a.k.a. "Snowbird") repeater.
Click on the image for a larger version.

It would seem that, in general, the feelings that the overlaps in coverage of the two repeaters will be quite minimal are borne out by the predicted contours.  The places where the two signals (signals from Scott's and signals from Farnsworth) are most likely to be approximately equal are:

• In Parley's, Big and Little Cottonwood Canyons (near the mouths.)
• Along the Oquirrhs, where Farnsworth Peak is shadowed by the range itself.
• In the middle of the Great Salt Lake, the Great Salt Lake Desert, and extreme north-western Utah (i.e. Raft River range, etc.)

Since the link between the two sites will be done on the 33cm band, it is important that there be a good radio path (obviously...)  Since there is direct line-of-sight between Farnsworth Peak and Scott's Hill, there was little doubt that there was going to be any sort of problem.  Nevertheless, we ran a path prediction between the two sites.  The resulting chart may be seen by clicking on the image to the right.  The parameters on which these calculations are based are as follows:

• Transmitter power:  +37dbm (5 watts)
• 40 feet of 1/2 heliax (approx. loss:  0.9db)
• 12dbi gain antennas, vertically polarized
• 3db isolator/cavity/duplexer loss
• -95dbm receiver threshold
• Frequency:  930 MHz

I'd be interested in any questions or comments on this data - click here to send an email.