Before you go too much further, make sure you read the following web pages:

• Receiving the WB7FID ATV repeater at your QTH - This page gives you an idea what you'll need to receive the ATV repeater - or maybe even if you can see it at all!
• Using VHF/UHF TV Antennas on ATV - Read this page to find out how well your existing VHF/UHF rooftop antenna won't work for ATV...
• The "P's and Q's" of video signals - You will find on this page (and many others on the web and in print) references to the "P" unit of ATV signal quality.  This page will give you an idea of what these ratings mean in terms of picture quality and signal strength.

The three ATV transmit antennas.  From left to right:  The "Ogden" antenna, the "Salt Lake" antenna, and the "Provo" antenna.  The Salt Lake antenna is directly below the light, the camera view being slightly blocked by the Ogden antenna.
Click on the image for a larger version.

About the Repeater's Transmit Antennas:

From the outset, the design goal of the ATV repeater was to provide reasonable coverage along the major population center of the Wasatch Front, covering from Tremonton (to the north) to Payson (to the south.)  Owing to geography and population distribution, it turns out that this will allow line-of-sight coverage from the repeater site.  The complication of this is that this is that the azimuthal difference between these two cities is about 149 degrees!  The problem with this?  You just don't get an antenna that is horizontally polarized that has that wide of a beamwidth and have much gain and have it be relatively small.

Here are a few things we looked at:

• An Alford Slot antenna.  This antenna can have good gain and be fairly omnidirectional and be horizontally polarized.  The problem with this sort of antenna is that they are rather large, awkward, and difficult to construct such that they work as expected.  Because of the wind load and space limitations on the tower on-site, this antenna was out of the question.
• A Trough reflector antenna.  While it is possible to get over 100 degrees of beamwidth and reasonable gain from a single trough reflector antenna (a very close relative of a corner reflector) that didn't quite give us what we wanted.  While a single trough reflector antenna would be quite large - it would be just manageable in terms of size and wind load.  Two of them, however (which would be required to obtain the desired beamwidth and gain) were out of the question.
• Multiple yagis.  It occurred to us that, perhaps, several phased yagi antennas could be used to provide the coverage.  Owing to the geography and population distribution it occurred to us that a small, wide-beamwidth antenna could be used to provide the "close-in" coverage of the Salt Lake valley and that larger, narrower-beamwidth antennas could be used to provide coverage of the more distant northern and southern population centers (e.g. Ogden and Provo, respectively.)  Needless to say, we chose this option.

This shaded relief map shows the shape and orientation of the antenna pattern with respect to the geography and the locations of the larger cities.  The "center" of this pattern is on a bearing of approximately 76 degrees relative to true north.  A cross marks the ATV repeater site.  Blue indicates lower altitude where yellow/reds indicate higher altitidues.
Click on the map for a legible version (165k jpeg image)

The transmit antenna system consists of three yagi antennas, all of them made by KLM.  The center antenna is a 6 element yagi (model 440-6x) which provides a rated 11.0 dbi gain while the other two antennas are identical 10 element yagis (model 440-10x) with a rated 13.6 dbi gain.  All antennas are fed in phase with equal amounts of power from a 3-way power splitter, resulting in a power of between 5 and 7 watts reach each antenna.

The patterns of these antennas actually overlap in order to prevent any "dead spots" or nulls along the coverage area.  In order to do this, the phase and orientation of the antennas need to be properly maintained:  Overlap could either result in the signals from the two antennas reinforcing each other, or in their cancellation.  If the latter were to occur, deep nulls may be present in the pattern.

The antenna sizes themselves are also no accident:  A lower gain (6 element) antenna was used to cover the Salt Lake valley - and that was a necessity as the valley being closer in, it represented a "wider" view from the top of the mountain - a fact accommodated by the wider pattern (60 degrees at the -3db points) of the lower-gain antenna.  This lack of gain is more than made up for the fact that everything in the Salt Lake valley is much "closer" than either Ogden or Provo.  In fact, downtown Salt Lake City is about 18 miles from the repeater site while Ogden and Provo just happen to each be about 40 miles away.

Being 40 miles away - and the fact that the coverage area is more-or-less a north-south ribbon, the subtended angle decreases as one moves either north or south from Salt Lake along the coverage area.  This works out nicely, as the higher-gain antennas (the 10 element yagis) help make up for the weaker signal due to the increased distance and their narrower beamwidths (48 degrees at the -3db points) are a good match for that narrowing angle.

What about coverage off the sides and backs of the antennas?  Unfortunately, this sort of thing is extremely difficult to predict.  We do know - from signal reports - that signals do radiate from the backs of the antenna.  We also know that these signals are quite weak.  In the Tooele Valley area, however, (directly west of the repeater) we know that reasonably good signals are obtainable using modest-sized (16 element) yagis.
 

This map and table shows the predicted signal strengths along the Wasatch Front and what sort of signal quality may be expected.  The different colors indicate the signal strength. (Refer to the text for further explanations.)  The legend shows predicted signal strength at the terminals of a typical 11 element (14 dbi) yagi.
Click on the map for a larger (readable) version (350k jpeg image)

Map colors and how they relate to signal quality and antenna requirements. WHITE and RED - Only a modest (5-10 element) yagi is required to obtain P4 pictures.  ORANGE - In the orange areas, a 5-10 element yagi will bring in P3 pictures while a 10-15 element yagi is sufficient to obtain P4 pictures.  YELLOW - In the yellow areas, a 10-15 element yagi will bring in P3 pictures while a 16-22 element yagi will bring in P4 pictures.  GREEN - A 16-22 element yagi will bring in P3 pictures, with the signals getting progressively weaker as you near the borders of the cyan and blue areas.  CYAN, BLUE and VIOLET - You probably won't have much luck in these locations.

The coverage map:

Taking a look at the coverage map, you will get an idea of how well the repeater covers the Wasatch Front.

It is important to note that these are just predictions.  There may be some local phenomenon or geographical feature that will degrade your signal somewhat - or make it impossible to see the repeater at all!  As you can see from the map, there are few areas along the Wasatch Front that are badly shadowed by local terrain - and this is the same terrain that affects the broadcast TV stations as well.  A few of these areas include:

• Alpine and northern Lehi in Utah County.  The traverse range blocks much of this area from a line-of-sight view of Farnsworth Peak.
• The river bottoms in Provo/Orem.  Sorry - but you probably already knew that...
• The extreme southern end of Utah county.  Parts of Payson and those communities further south are blocked by Lake Mountain.
• The river bottoms and parts of Ogden.  The "Hill" (e.g. the hill upon which the Air Force Base sits) blocks portions of the Ogden and North Ogden area.
• The city of Tooele:  If you use the '62 repeater, you'll know that the mountain blocks its signals pretty well over much of the city - especially the southern portion.  This repeater is similarly affected.
• Magna:  The city of Magna is close enough to the Oquirrh mountains that geographical features of the mountain range will directly block the signal.
• There may be others...  If you can't clearly receive channels 5, 13, 14, 24, and 30 due to blockage, then you probably won't be able to see the ATV repeater, either.  (Its in about the same location as those TV stations...)

How good are these predictions?

As with any predictions of propagation, these are merely guidelines.  Your results may vary - and those results will be directly proportional to how good of a signal you have to fetch out of the air, and how good your receiving system is.  Although they are already mentioned on the Receiving the WB7FID ATV repeater at your QTH page, here are a few things that are worth repeating:

• Your existing rooftop VHF/UHF antenna will make a terrible ATV antenna:  They just aren't designed to work at 70 cm.  Go ahead and try it if you live in a "Red" or "White" area - but don't be surprised if it doesn't work too well - and remember that any splitters will degrade your signals.  A commercial antenna-mounted signal amplifier will likely help (especially if you have some splitters) but you really do need an actual 70 cm antenna to do a good job. (Note:  If you don't live in or near an area shown in RED or WHITE on the map, then don't expect good signals at any rate - but it might be worth trying.)  For more information about how well VHF/UHF TV antennas work for ATV, go here.
• Remember that the signals from the ATV repeater are HORIZONTALLY polarized.  If you have an existing 70 cm antenna, go ahead and try it - but if it is vertical, don't expect it to work well at all! Yes, cross-polarization can make a huge difference!
• Use good quality coaxial cable.  Do not use any more than 10 feet of RG-58 or RG-59 to connect your antenna (unless you have a preamplifier in front of that coax.)  It is also worth noting that good quality RG-6 has only a bit more loss than "average" RG-8 does.  You might worry about the fact that your 70 cm ham antenna is 50 ohms and RG-6 is 75 ohms:  Don't worry - the losses cause by the mismatch will be minimal.  You might not want to use RG-6 if you plan to transmit on 70 cm, though... (Note:  Don't try to put a UHF connector on RG-6 cable:  You can get adapters to convert to/from the "F" connectors on the RG-6 cable from Ra-Elco or from other sources - look in the 'fone book...)
• An antenna-mounted low-noise 70 cm amateur band GaAsFET preamplifier will make a world of difference in the quality of signal that you receive.  An advantage of having mast-mounted preamp is that the losses caused by the coax following the preamplifier are much less important.  If you have such a preamp, make sure you take the proper precautions if you plan to transmit! (You don't want to blow up that nice preamp, do you?)

Go to the Utah ATV Home Page...