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Author Topic: TVI  (Read 665 times)
K4FJR
Member

Posts: 1




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TVI
« on: April 26, 2003, 10:43:21 AM »

This is the first time I have had this problem so I need some help. I just got back in ham radio after being out for a long time. I have an Icom 718 and AL80 amp. No problems when running the 718 barefoot. When I crank up the amp the TV upstairs has voice and lines in it. I  cannot get on the air under these conditions.
What can I start with to eliminate the problem.
I have comcast cable if this will help.
e-mail contact is tenspeed23@comcast.net.
Any help is appreated. Antennas are 80 and 40 meter wire antenna and a vertical for 10 meters
Max
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WB2WIK
Member

Posts: 20561




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TVI
« Reply #1 on: April 28, 2003, 02:25:33 PM »

You shouldn't be able to interfere with cable, so it would be interesting to see how this is happening.

Possibly you're interfering with the TV receiver itself, and not necessarily the cable system.  One way to tell would be to plug the cable directly into the TV, without any converter.  If you do interfere with it that way, note the channels that are being interfered with.  Then, unplug the cable and try plugging in a TV antenna (even rabbit ears) and see if the interference on those channels is better or worse.

Assuming the cable is intact, well shielded and not defective in any way (quite an assumption!), it ought to be very immune to RFI; however "common mode" interference caused by the cable outer shield picking up your radiated signals is still pretty common, and can be fixed using clamp-on ferrite RF chokes snapped directly over the cable, near the television receiver.

Then, there's always the possibility of the AC line conducting RF interference from your amplifier through your house wiring and into your TV receiver.  With the AL80, in particular, that's a fairly common thing since the AL80, AL80A and AL80B have very little power line filtering in them.  I have an AL80B, where I had to add ferrite toroids *and* disk ceramic bypass capacitors to the AC line where it enters the chassis in order to eliminate some conducted interference to my kids' Nintendo games.  Prior to doing that, using the amplifier would shut the games "off."  No damage was done, but that was very inconvenient!

WB2WIK/6
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KG6GOA
Member

Posts: 10




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TVI
« Reply #2 on: May 08, 2003, 03:29:25 AM »

hello max, my name is bob K6ZOE new call. had the same problem. went to radio shack, got a AC line filter, and a high pass filter and bingo problem gone 98%. the rest of the tvs in the house never had a problem. i have a house that was built in 1952 no ground wire at plugs. this is part of the problem..73 bob
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