From: jack@myamiga.mixcom.com (Jack Decker)
Newsgroups: rec.video.cable-tv
Subject: Re: AM Radio Interference...
Date: 26 Aug 92 01:42:10 GMT
Article-I.D.: f8.1992Aug26.244d7
Organization: Northern Bytes BBS - Sault Ste. Marie, MI U.S.A.

In article <HOGAN.92Aug10130753@cujo.csl.sri.com> dated 10 Aug 92 21:07:53 GMT,
hogan@csl.sri.com (Emmett Hogan) wrote:

 > I am having a really strange problem on one of my TV sets in our new
 > house, namely I am getting a certain AM radio station coming through
 > the TV.  It's a classical station (KKHI in the bay area) which has
 > it's broadcast towers about two miles from my house.  I was having
 > this problem with the phones also, but I just went to the AT&T store
 > and picked up a few filters (at a mere $17.00 a piece !), which got
 > rid of the problem there.

I could have saved you a pile of money... you could have gone to Radio Shack
and picked up some capacitors (at probably about 50 cents or a buck apiece) and
fixed the problem, if the station is really two miles away.  You take a .02
microfarad capacitor (rated at 400 volts or higher - higher is better to
protect against surges) and connect it between the red and green wires at a
convenient point, probably at the network interface box.  If a ground wire is
available, you can get better supression by using two capacitors, one between
the red wire and ground and the other between the green wire and ground.  I
used to live across the street from an AM station and this is exactly what the
phone company did, except they put the capacitors inside the phones (this was
back when they owned the phones!).  BTW, chances are you could have got an
equivalent of those $17.00 filters FREE from the telco... all they really are
is a choke coil that blocks out radio frequencies.  They are more effective
than the capacitors, but are probably severe overkill in your case.

 > The cable people were alot less help, they
 > simply told me to complain to the radio station and if that didn't do
 > any good, then to complain to the FCC...yea, like this radio station
 > is going to crank down just because it's interferring with my cable tv !!

 > Someone else mentioned trying a different length cable to the TV, as
 > the current cable might just be the right length to act as an antenna,
 > I haven't tried that yet, but will tonight.

 > My question to this group is, has anyone else had this problem?  If
 > so, what did you do about it?  Is there really no such filter I can
 > put on the line?

I've never heard of the audio being interfered with, but we had one TV where
the AM station put lines in the video!  The solution?  Same as for the phone,
more or less.  It turned out that the radio signal was coming in on the power
line, so they connected a .02 microfarad capacitor between each wire of the
power line and the TV chassis.  Now, that was an old tube set that actually had
a common chassis, in a transistorized set you might want to put the filtering
behing a power transformer. In any case, you will probably need to open up the
set and if you don't know how to do that, you probably should take it to an
expert in order to avoid damaging your set or getting a severe shock (which can
happen ever after the power is disconnected... you have been warned!).

Jack

Jack Decker                               | No, I don't own an Amiga; I just
Internet address: jack@myamiga.mixcom.com | get Internet mail via a gateway
Fidonet address:  1:154/8                 | system that runs on an Amiga.
Newsgroups: rec.video.cable-tv