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Old 22-Aug-2015, 3:16 PM   #29
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,516
Originally Posted by No static at all View Post
You certainly don't need more amplification. What you do need is more signal AT the antenna.

How close are your antennas to each other? Can you take a pic & post it?
I think your post #18 was on target. The increase in antenna separation, and a little more height might help, but the trees are a big problem. Maybe Mike can have a few critical trees topped without having to remove them completely.
Originally Posted by Calaveras View Post
I have a couple of examples of vegetation affecting DTV signal strengths. The spectrum analyzer displays in this post show the difference between my antennas with the tower fully cranked up at 71' and fully cranked down at 36'. The yellow trace is tower up and the magenta trace is tower down. One image is VHF and the other three are spaced across UHF.

Attached is a picture taken from just below the UHF antennas at 69' looking west towards my local stations. (Camera was mounted on the mast and the tower was cranked up.) There is a clear shot to the 2nd edge that the signals pass over. There is vegetation on that hill. When the tower is cranked down much of the foreground vegetation blocks the view to the hill. There is as much as 20dB attenuation from the vegetation. UHF is generally affected more than VHF. Even though the signals look strong enough to receive, only 2 out of 9 stations will decode with the antennas lowered and their SNRs are very low due to severe multipath.

Getting the antennas above the vegetation is the difference between useable OTA and no reception.
Attached Images
File Type: jpg ChuckTrees1WalnutGrove_1.jpg (288.1 KB, 298 views)
File Type: gif ChuckTrees2KVIE%20KXTV.gif (23.3 KB, 337 views)
File Type: gif ChuckTrees3KMAX.gif (24.2 KB, 310 views)
File Type: gif ChuckTrees4KCRA.gif (24.2 KB, 320 views)
File Type: gif ChuckTrees5KQCA%20KTLN%20KSPX.gif (24.3 KB, 335 views)
If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 23-Aug-2015 at 2:48 AM.
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