Intermittent Interference

[voidcomp]

I'm trying to troubleshoot the source of intermittent interference to my TV signal. It happens specifically on physical channel 45 which also has the weakest reception of all channels, yet comes in crystal clear otherwise. According to TV Fool the channel is in green territory, 37.4 dB.

http://www.tvfool.com/?option=com_wr...46ae29a893000d

The interference manifests itself as picture freeze lasting 1 to 2 seconds, repeating at times less than a minute apart sometimes, at other times no freezing for 10 to 15 minutes. It happens day or night and doesn't seem to be any better or worse under different weather conditions.

It is located in an attic without any electrical wiring in its directional path, at the end of the house closest to the tv towers. There are trees in the path. None at the present have leaves.

Not sure if this makes any difference but there's a police and fire transmitter directly, and I mean directly in line, roughly 1/2 mile away. Could this possibly be the source of interference?

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What is the Make and model number of the antenna??

Or if unknown , what antenna in the picture looks the most like the antenna. www.kyes.com/antenna/pointing/pointing.html

Or can post a picture of the antenna.


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Attics Are Not a reception friendly environment and Never Will be a Reception friendly environment.

The most likely cause of poor reception is --> the antenna is in the attic.

[voidcomp]

Winegard 7694P pointed 163 degrees.

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---->Test<-->Reception with the HD7694P antenna above the peak of the roof in such a manner that the roof and and building are not , obstructing , impeding , blocking , reception in the directions of reception.

[voidcomp]

Thank you, but since I have no assurance that relocation will, in any manner, remove this interference can you or anyone else offer speculation as to whether the police/fire transmitter is a possible cause, even if secondary to attic problems?

[GroundUrMast]

It's not a stretch to speculate that a transmitter in the direct line of aim might be a source of interference.

Moving your antenna is the least expensive next step. The goal would be to find a location that has higher quality desired signal and coincidentally, low levels of interfering signal. Changes of less than a foot have been known to produce dramatic changes. You'll may need to try many positions, patience and persistence may be needed.

If one has access to a spectrum analyzer you would have a real chance at proving the existence and source of interference. I don't have access to such a device now that I'm retired from an industry that used such equipment. I can't justify the purchase or rental of a piece of equipment with the price tag of a new car.

[ADTech]

Is it possible? Yes. Is it probable? :shrug: Don't have any way of knowing without either looking at the signal on a spectrum analyzer, unfortunately. If you were able to determine what frequency(ies) the public service agencies are operating on, then you could install a frequency selective filter to attenuate them from the input of your set(s).

For testing, you could use the UHF input of a UVSJ to trap out the VHF band since that appears to be where most of your local police dispatch appears to operate. That would at least give you an idea if interference from the VHF band is the issue.

Unfortunately, many of the other public services use UHF frequencies almost adjacent to UHF channel 14 (450-470 MHz), so filtering them out would be a lot more difficult and you won't be able to pick something up at Radio Shack that will do the trick.

[voidcomp]

Thanks for the replies. It appears getting a spectrum analyzer will be as difficult as asking police/fire to stop transmitting lol. Assuming it is the problem of course.

Would it be safe to say that the weakest channels would be the first to exhibit interference issues? All other, stronger channels aren't affected.

[GroundUrMast]

Originally Posted by voidcomp

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Would it be safe to say that the weakest channels would be the first to exhibit interference issues? All other, stronger channels aren't affected.

Particularly true if the interference is from a broadband source such as an automobile ignition system, florescent light fixture, computer, motor, etc. Less likely if the interference is from a fixed frequency source such as a licensed transmitter.

The the fixed frequency source is quite likely to affect only one or two channels. FM broadcasts are a common source of single channel interference to OTA TV. Of course, it could be coincidence that the weakest TV signal happens to be the victim of a fixed frequency interferer.

In the cases of fixed frequency sources of interference, the likely frequencies to be interfered with will be odd multiples of the frequency transmitted. In your case, real CH-45 is 656 MHz to 662 MHz. So your first suspects would be operating on frequencies 1/3, 1/5 or 1/7 of the frequcie range of real CH-45.

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Tv antennas do not pull signal out of the air.

Antenna amplifiers do not pull signal out of the antenna.

The best way to increase received signal strength and reduce interference at/from your own , attic , inside of building , roof and building , is to install the antenna above the peak of the roof in such a manner that , attic , inside of building , are not , impeding , obstructing , blocking , reception in the directions of reception.