TV sound interferance

[removeb4flight]

My TV in a back bedroom has a problem with channel 3 sound. Whenever the picture has a lot of white and contrast to it, the sound gets a loud crackly type of static. Could this be too much signal level at the TV? I have a distribution amplifier to send the signal from the antenna to several TV's. The back bedroom is fed by RG-59 about 50 feet long. It gets the signal out of the box on an output labeled "distant TV" which has more gain than the "local TV" output. None of the other channels seem to have this problem; 6, 10, 13, 16, 22.

[Mr T]

is there a VCR on this TV?
how many tv's are connected to your dist amp? what is the gain of the amp?
Does your amp have a adjustable gain? any splitters or splices in the path to this TV?

bypass the amp and see what happens.
Your signal may be too hot. Ch 3 is a sensitive channel to begin with. all your radio stations are just below it's frequency. If your tuner has poor selectivity, it can get interfereence here easily.

[removeb4flight]

I have 3 outputs for distant TV and one for local TV. The feed to the back bedroom had no splitters on it. I tried putting a splitter on it to see if it might drop the signal level to get rid of the interference. NO change noticed.
The dist amp is a Channel Plus, but I don't know what gain it produces. I'll try to find the manual for it. The affected TV is connected with a VCR ahead of the TV, ie. I am using the VCR to tune the signal which is then sent to the TV. I'll try taking the VCR out of the system.

[ElectricNut]

I suspect you'll find the VCR is your problem. I have a Philips/Magnavox VCR that does the exact same thing when I use it as the tuner. I've seen several of these cause similar problems in my field work, also. Are you amplifying a cable TV signal, or just over the air antenna channels?

[removeb4flight]

Yes, it was the VCR. I took it out of the loop and the sound is fixed. I am sending over the air signals, a Sat TV, and home security camera through the dist amp. I'll re-wire the system so that I can tape off a different input. What makes the VCR screw up the sound on Chan 3? Just wondering.

[Mr T]

Try ch 4 (dont forget to flip the switch on the VCR)

Too many possibilities to listhere. Down at my parents, Ch3 was a heavily used chanel with a strong signal, we almost always had to use 4. Dont have the problem here. We are 50 miles from our local NBC station, yet we get a clearer picture with NBC via antenna then with cable. We are out in the sticks and need a cable amp to get a solid signal, when we hooked up they said we had just about enough signal for 1 TV, but no more, 3 TV's ok with the amp.
You could be the opposite. You may be close to your area's dist amp and it may be too strong of a signal.

[ElectricNut]

The cable company I work for actually manages a few of those cable systems there in Northwest Ohio, in Payne and Convoy to be exact. It's truly a crime the way those older systems are being let go. They're long overdue for being upgraded. The signal at the tap will suffice for one, maybe 2 TVs, but more than that you need an amp. In the city I live in (with a modern CATV system) in general, you can expect on average to run 4-6 TVs in a normal house without an amp. That's the way it should be everywhere.

[suemarkp]

I think the key is that you said you're using the VCR to tune the channels. If that is the case, your VCR breaks the tuned signal into its audio and video components (so they could be recorded onto tape) and also multiplexes them together again and sends them to your TV on a single channel (usually switch selectable on the back as 2 or 3). If you have the VCR set to use channel 3 for reboradcast to the TV and you have a local broadcast channel 3, you could be getting all kinds of interference. You need to have good cables that have good shield integrity if doing this. You really should use a channel from the VCR that doesn't match an over-the-air channel if possible (so pick channel 2 if 3 is a broadcast channel and then set the TV to use channel 2).

Another problem that can happen is with the levels inside the VCR. If things are out of adjustment, the chroma or luma signals can bleed over into the audio carrier and you get the hum that heard. I think there are other problems that can cause this too, but I don't think you'll want to bother with fixing them. Its cheaper just to buy a new VCR than to attempt to fix yours.

Finally, there is one other option. If your TV has baseband video inputs (three phono jacks typically colored yellow (video), red (audio R), and white (audio L)), you could connect the TV to the VCR via these three wires instead of the coax cable you're now using. This will keep the audio and video signals separated so that any video bleed over won't affect the audio. You'll have to tell the TV to use this input now instead of the RF connection you had been using. Many older TV's won't have this type of input.