[amsat-bb] Re: 2 Meter TV Interference

Ernie Howard w8eh.ernie at gmail.com
Wed Dec 7 13:31:17 PST 2011


In all the replies that I read so far I have not seen much help for you. 
Here are a few tips.

The problem is your neighbor's amplified splitter can't handle a strong 
nearby signal. Your neighbor has to fix the problem.

The only solution is for your neighbor to remove the powered splitter 
from the antenna system. All consumer type powered TV splitters are 
broadband and will amplify everything from 50 mhz to 700 mhz. That is 
the problem, since your two meter signal is in the middle of the amp's 
passband. Any strong signal in the range from 50 to 700 mhz will swamp 
the transistors in the amplified splitter and block TV signals from 
being received. After he removes the amplified splitter, he can replace 
it with a passive splitter. Hopefully he is close enough to the TV 
stations that he doesn't need amplification. If not, he may need to 
consider a proper high gain antenna outside.

The only other solution (as your local ham friend suggested) would be to 
get a stopband filter(blocking 144 to 148), and have your neighbor place 
it in between his antenna and TV amplifier. The problem is that these 
type of special filters are not cheap. And the neighbor might blame you 
if something happened to his TV..... ICE has a filter for this 
application. Not sure if they are still in production. 

At my QTH I have to newer HDTVs connected to a high gain directional 
antenna pointed to stations 30 miles away. They are fed by coax with a 
PASSIVE type two-way splitter. (No amplified splitters, no special 
filters.) My two meter or 70 cm radios do not bother reception on either TV.

Your problem is similar to the problem that I run into when camping with 
my RV. The 'batwing' type antennas that are on most RV units have a 
built in amplifier in the head outside. ANY signal, even down to 1/2 
watt, overloads my amplified TV antenna in the RV and any other RV close 
to my 2 meter or 70 cm antennas.

To the guys who say he is running too much power... that isn't a fix. 
There are other uses for his 'power' other than talking to satellites. 
This problem will prevent him from using his two meter radio any time at 
his house.

Ernie W8EH

On 12/6/2011 10:17 PM, Wyatt Dirks 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 downlink.
> The problem occurs while I am transmitting. The neighbor says that his tv receives the interference in that the picture is disturbed and sometimes cuts out completely. He is getting his tv from hdtv over the air. He has an antenna in the attic that goes to a powered splitter which then goes to several tvs. That is about all i know on his setup but I do know that if he cuts the power to the splitter he receives nothing. Also the problem seems to be on every channel.
> 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.
> If anyone has any ideas on what would solve this problem and could share that would be great.
> Catch you on the birds
> Wyatt AC0RA
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