Google Earth helps point OTA antennas

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anik

Thread Starter
SatelliteGuys Pro
Aug 28, 2004
356
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U.S.A.
I am uploading a ZIP file that contains a couple of overlays for Google Earth. tv.kmz contains data for the United States, and can.kmz is data for Canada. When you load these files into Google Earth, it will display every television transmitter shown in this FCC list:
http://www.fcc.gov/oet/dtv/appendixb/AppendixB_stations.lis
Which shows the (supposedly) final channel assignments after the 2009 cutover date. I found some similar data for Canada in a .pdf file that I can't seem to locate again, but unfortunately that data is a couple years older and therefore probably not as accurate. Actually the Canadian data seems a bit less accurate than the U.S. data to begin with, in that when you zoom into the U.S. coordinates you can often actually see the tower if you look closely, and generally it's very close to the dot. In Canada you are lucky if the coordinates are within five or six blocks of the tower, assuming you can see it at all. Another weird thing about Canada is that apparently they don't assign call sign letters to all their stations. Still, the Canadian data is probably accurate enough for aiming unless you live within a couple miles of the transmitter, and if you're that close you probably can see the tower from your home.

So the idea is that you find your home (you can create your own placemark to make it more visible), the back off and see how the stations are arranged around you. In some cases the transmitters are nowhere near the actual city of license. Then, if all the stations you want to receive are more or less in the same location (as is often the case) you can pick a station that is more or less in the center (relative to your location) and aim your antenna for the highest gain on that station, and hopefully you'll still get a decent signal on the ones that are a little bit to the left or right of where you are pointing.

You may find that one particular station is in a totally different direction from the others and in that case you can use a Channel Master Join-Tenna (Google it) and use a separate antenna for that station, PROVIDED it's not adjacent to a desired channel. But remember that DTV channels can be adjacent to each other, and you can't use a Join-Tenna if a wanted signal is on an adjacent channel (remember that in the VHF band there are some gaps in frequencies, such as between channels 6 and 7, so adjacent channel numbers may not actually be adjacent).

My problem is that most of the stations I want to pick up are in one direction, and are all over the band (UHF and VHF, so will probably just use a deep-fringe all-channel antenna for those). Then there's a channel 13 that's in a direction all by itself (strong signal, one of those you could almost pick up with a bent coathanger), there's a channel 9 that's in yet another direction (more distant than the others but still a reliable signal with a good antenna, BUT a wanted signal is on channel 8 so can't use a Join-Tenna on that one), and then there's a bunch of UHF's from another, even more distant location that would probably still be receivable on an intermittent basis (e.g. on good weather days) with a good UHF-only antenna. I'll probably write off the last group but it pains me that I can't come up with a good way to bring in that channel 9 signal. Note that a rotor is out of the question as this is feeding three TV sets that can all be in simultaneous use on different stations. How the heck do cable companies combine channels from different directions?

One other note, this does NOT show relative signal strengths (wouldn't it be nice if you could overlay the grade A and grade B contours for each transmitter - well, I can dream, I guess). And even if it could, that wll probably change quite a bit as each station completes its DTV conversion. So it goes without saying that a high-powered station that's further away could easily deliver a stronger signal than a lower-power station that's closer.

Anyway, hope someone finds the Google Earth overlays useful. If you find a better or more current source of transmitter site data, post the link in this thread and I'll try to update the overlays if I can figure out how. By the way, if you do find these useful and you know how to do it, please feel free to upload them to Google Earth's user-contributed database, or any other site where the data might be welcomed. I tried to upload them and was told I needed a newer revision of Google Earth, but then when I tried to upgrade it told me I already had the newest version - go figure!
 

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