[amsat-bb] Re: 2 Meter TV Interference

Bob Bruninga bruninga at usna.edu
Wed Dec 7 10:24:30 PST 2011

HPF above 500 MHz?  Then the TV would not be able to see anything but a few
UHF channels.

What is needed is a stub filter.  Just a piece of open ended coax 13" long
"T"ed into the antenna lead.... 

The 13" is about 66% of a quarter wave at 2 meters.



-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Gordon JC Pearce
Sent: Wednesday, December 07, 2011 3:02 AM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Re: 2 Meter TV Interference

On Tue, 6 Dec 2011 21:17:55 -0600
Wyatt Dirks <wyattdirks at msn.com> wrote:

> Just recently I have been having troubles with a neighbor while I am
working the FM satellites(SO-50 and AO-27). The setup I am currently using
is my mobile setup because I am unable to put a base station up for many
reasons. I am using a FT8900 with 50 watts out into a 1/4 wave or 1/2 Larson
mobile antenna.The 1/4 wave is mounted permanently via a hole in the roof of
my truck an the 1/2 wave is mounted on a mount opposite the factory
installed FM/AM radio whip. It doesn't seem to matter what antenna I use for
the problem to occur. Then I use either the arrow antenna or my cju for the

Use 5W into a hand-held Yagi.  You'll get far better results.

> Today I had another local ham over at the request of the neighbor and his
mobile Kenwood radio did the same thing to the neighbors tv when he
transmitted on 2 meter with 50 watts out. He also recommended that they get
a filter. I did not see the specs on the filter nor do I know what bandwidth
it was for.

What you want is a highpass filter that will lop off everything below
500MHz.  The chances are that your TX output is clean enough but the little
amplifier in the splitter for the TV is causing all sorts of intermod - and
probably covers from broadcast VHF radio to the top of the TV band.

Gordon JC Pearce MM0YEQ <gordonjcp at gjcp.net>
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