Reception Issues


Hi everyone,

Last week, I helped a buddy 100 yards away install a HD1850 antenna to a single Sony TV. We guessimated where to aim the antenna and he received all 38 channels expected from Washington D.C. (We're about 35-40 miles South of the city).

This week, I installed the same antenna with a CM-7777 pre-amp because my RG-6 from the antenna into the house is 75-80 feet long. The pre-amp then feeds a CM-3414 distribution amp to feed four Samsung TVs around the house. Again, we guessimated at aiming the antenna toward DC. My TV locked onto 40 channels. However, I was getting intermittent snow and signal drop outs.

I decided to use a compass app on my iPad to better aim the antenna. All the Station databases said most the network stations were at/around 31 degree azimuth. So I moved the antenna about eight degrees East (from 23 to 31). This time I only received 38 stations but was still getting intermittent snow and drop outs. I assumed it was due to cloudy rain cover, but the next day the signal problems continued with beautiful weather.

More internet research at another TV station database said azimuth should be 31 true, 41 magnetic and I knew I was at 31 magnetic, so I, again, climbed up on the roof and moved the antenna another 10 degrees to 41 magnetic. I was sure this would give me all the stations in perfect reception. Nope! Now I only get 15 stations but the one's I get are rock solid. The station I most wanted was WJLA (ABC affiliate) which is indeed picture perfect. But looking at the map, if I get this station, I should be able to get nearly all the stations; they are are at 30-34 degrees.

Couple questions up front:
1) If you unplug the pre-amp, will the signal still continue through the amp or do I need to bypass on both ends?
2) Why would I get more channels when the pre-amp is unplugged?
3) Does weather (rain and clouds) affect reception? I assume it does (like satellite reception).
4) We have two large trees in our front yard. Could those affect reception as they move with the wind? If this is the problem, I'm screwed).
5) Initially I received all VHF and UHF channels on this list. As I re-aimed the antenna, my channel list got shorter but the signals were stronger. How can I get some channels in the station row (31 degrees) but not others (with or without the pre-amp)?

All my info is below. I'd appreciate your help or suggestions.

TV Fool
  • HD1850 Antenna
  • CM-7777 Pre-Amp
  • CM-3414 Four-Port Distribution Amp
  • 34 feet off the ground
1) No. The un-powered amp usually turns into a 30 dB attenuator. It must be fully bypassed.

2) Most likely, you were overloading the system. Waaaaaayyyyy too much amplification!

3) Yes although the effect is far less severe than for satellite signals.

4) Absolutely. If the wind blows and the signal breaks up, it's the trees.

5) You have to get rid of the overloading situation first.

You have a 160 kW station well within the beamwidth of your antenna that's only 10 miles away and is LOS. You may have to notch it out to make the rest of the stuff work properly. Also, make certain you are using the FM trap if you continue to try the CM 7777.
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