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Old 2-Apr-2011, 4:34 AM   #1
Yaguy
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RE: Cross-hatch type Interference

I hooked up a new Zinwell ZAT-970A digital to analogue converter box and noticed that there are diagonal lines going arcross the screen from left to right: ////. (The picture is clear but the interference is about the same on all channels.) It might be called Cross-hatch interference. It is constant and the lines are about 1" apart on a 27" CRT Toshiba TV. Is this a symptom of bad coax or water infiltration, antenna age, or just a radio frequency, be it FM or another band that the outdoor combination VHF/UHF/FM antenna is receiving? It is a Radioshack RS VU-160XR. I just would like to know if anyone here has had this type of interference or knows what it might be and how to eliminate it as much as possible. Thanks.
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Old 2-Apr-2011, 7:13 AM   #2
John Candle
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Tv Antennas and Reception

Yaguy has posted several times before. What are you using of connection from box to Tv. Does the Tv have connection jacks other then antenna in ?? If using coax to connect the box to the Tv then change from channel 3 to channel 4 or from 4 to 3.

Last edited by John Candle; 2-Apr-2011 at 7:26 AM.
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Old 2-Apr-2011, 7:24 AM   #3
Yaguy
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Should I have put this in another thread- mainly where I was previously talking about reception some months back? I was thinking that this was an external interference RF or electrical problem, and I was hoping that someone here might know. Thanks John Candle. But I can post back in the reception thread.
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Old 2-Apr-2011, 7:33 AM   #4
John Candle
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Tv Antennas and Reception

What I am saying is the previous posts have the tvfool report and the radar report can be looked up. You need to be here in the help with reception.
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Old 2-Apr-2011, 7:34 AM   #5
mtownsend
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The first things I would check are:

1) Are the converter box and TV grounded properly? If there is anything wrong the with grounding of either device or with the ground wiring of the house, there can be a "ground loop" situation (http://en.wikipedia.org/wiki/Ground_...electricity%29).

2) Could be noise on the power line. Can you test with a power strip that has EMI filtering?

3) Go through a process of elimination to try and isolate the cause. For example, swap out the converter box and feed the TV with a different video source (like a VCR, DVD player, or a different converter box) that has the same kind of connection. Try a different set of cables. Take your converter box to a different TV and try it.



A few questions:

Do you have any amps or any other powered devices between the converter box and the antenna?

Is the connection between the converter box and the TV using "RF out" or "video out"?



General thoughts:

This does not sound like an antenna issue or a problem with signal detection. If you are getting a picture out of the converter box, it means that it is detecting a clean enough signal (good SNR) to decode the digital data and play the video streams. If there was a problem locking on to the signal, then you might see picture drop-outs, freezing, or some blocking artifacts, but would not see diagonal bands like the ones you're describing.

This seems to imply that the problem must be in the converter box, the TV, or somewhere in between.

Electrical problems can cause symptoms like the ones you're describing, so that's why I'd check those first.

You didn't mention having an amp, but if you do, you want to make sure that you're not somehow sending power to places it's not supposed to go (some amps are powered via the same coax that carries the signal, so you want to make sure the power is not being sent into the converter box or any other device that isn't expecting to receive power that way).

It could also be a bad converter box, bad cable, bad connector, or maybe the TV is going bad.

Although "interference" from other signals (FM, AM, TV, etc.) might be possible, the chances of that being the case seem to be exceedingly remote. You don't happen to live right in front of a transmitter facility, do you?
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Old 3-Apr-2011, 2:08 PM   #6
Tower Guy
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Quote:
Originally Posted by Yaguy View Post
I hooked up a new Zinwell ZAT-970A digital to analogue converter box and noticed that there are diagonal lines going arcross the screen from left to right: ////..
I'm going to take wild guess that you have both a converter box and a VCR set to the same channel. Put one on 3 and the other on 4 and see if the herringbone pattern goes away.
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Old 3-Apr-2011, 4:11 PM   #7
John Candle
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Tv Antennas and Reception

The situation is resolved at Yaguys other post http://forum.tvfool.com/showthread.php?t=1102
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Old 3-Apr-2011, 6:25 PM   #8
Yaguy
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Thanks Tower Guy and mtownsend

I put my post over to where, months back, I initially was talking about my reception as recommended by John Candle.

http://forum.tvfool.com/showthread.php?t=1102

I had the D2A box set to use the RCA outputs and it was in fact some interference from going through the Toshiba DVD/VCR player, and running to the TV first then out to the VCR fixed the interference on the TV. Still have to see if I'll be able to record with the VCR this particular way.

And thanks mtownsend for the very detailed process of elimination steps. Very handy to have. My transmitters, are about 9 to 10 miles away on Mt. Seymour for TV and radio, and additional radio in Vancouver might be 8 to 10 miles awy. I had thought, initially, I might be picking up electrical interference from a power line across the street in front of my house or some type of wireless device nearby, but so far things seem to have worked out by putting the D2A box to the TV in Video 1 then the TV Out to L1 in the VCR.

Again, many thanks for you taking the time to thoroughly answer and provide help.
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Old 3-Apr-2011, 6:47 PM   #9
John Candle
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Tv Antennas and Reception

It is best to keep ALL information on the original post that was first started , Making new posts each time makes more and more and more confusion. When you add to the original post it will be updated and every one will see it. Now you have more then one post and every one is answering questions on different posts and confusion is the the rule of the day.
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