Loss of channel question

nrvcad

DTVUSA Rookie
#1
I live in a mountains area in sw VA, I have a high gain Radio Shack antenna, with a Channel Master 7777 (26dB) amplifier mounted at the antenna above the rotor about 35' in the air. This summer I lost significant signal strength on (1) channel, FOX on UHF Chan 17. All the other UHF channels are fine. Everything worked fine since before the Digital switch. I looked at TVfool, for my area, and I should have plenty of signal BTW all of the DTV transmitters are located on the same mountain near Roanoke Effective ERP: 81.518 kW (Adjusted according to your location) Distance: 24.4 miles Azimuth: 78 degrees Compass: 85 degrees

I have (2) Digital Stream DTX9950 converters, that come from a splitter, one for the bedroom. The lack of signal is on both, so its not the converter. I don't know what changed this summer. Any Ideas why one channel changed?
 
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#2
I would suspect that the leaves on the trees have caused a null for UHF 17 where the antenna is now located. Moving the antenna up or down a few inches would be my first attempt to getting back 17. I am assuming you have tried re-scanning your converter boxes & that the 7777 isn't overloading your system. Can you post your TV FOOL report?
 

Tower Guy

DTVUSA Member
#3
This summer I lost significant signal strength on (1) channel, FOX on UHF Chan 17.
Here is your TV fool report
TV Fool
Note that channel 17 is much weaker that the other stations. This is due to a directional transmit antenna. It's also adjacent to CBS on channel 18 and much weaker.

I'm concerned about the strong FM signals near you. WWBU on 101.7 has a calculated signal strength of -16 dbm, which is 59.5 db stronger than channel 17. The converter boxes that you have are not equipped with FM filters. The 7777 preamp does have an FM trap and I hope that you have it switched in. Even then the FM filter may not be effective enough and is surely not effective on the non commercial stations below 91 mhz.

Because of the strong FM stations, I would not have used a 7777 in your location. FMfool report.jpg
 
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Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#4
:welcome: nrvcad,

I had a personal message from an engineer at that station and his advice to you and the advice given above is excellent. :thumb: He forwarded a photo of your antenna and your TVFOOL report and he indicated you have recently replaced your coax with new RG-6.

My thoughts: did you replace the balun on the antenna? Next, are their any open 'female' "F" fittings in the system, perhaps on your splitter or on the CM-7777? It is possible for RF signals to enter 'open ports' and play havoc and this includes strong FM signals Tower Guy mentioned. Have you tried any other antennas in different locations and heights on your roof or an indoor antenna? Do your converter boxes offer a diagnostics screen showing 'signal strength' or 'signal to noise' S/N?

Please keep us posted and good luck.

Jim
 

nrvcad

DTVUSA Rookie
#5
The problem is fixed. Apparently the antenna either shifted, and the trees in my back yard grew into the path of the signal. We lowered the antenna and rotated it about 10 degrees (now almost due E) and the signal went up to about 72-75 on the signal strength meter. Again thanks for everybody's help have a GREAT day - Jim
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#6
Jim,

Congratulations! Glad it all worked out. You might want to zap the station a note to verify to them this problem was on your end.

Jim
 
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