TVi – The battleground

Television interference, what a complete nightmare. When I passed my foundation licence and started transmitting on 2m @ 10 watts,  TVs throughout the house all went haywire.

We were running a Global (or equivalent) F140 amplifier/splitter 4 way, to take signals from the loft mounted (not ideal, being in a bungalow) TV antenna and distributing them to some TVs around the house.

So, on day two of being on the air, I replaced the loft antenna with a high gain, and replaced the shoddy down feed coax.  This did seem to improve things, until recently, when I moved into a new shack location and was spending more time on 2m and 70cm. Also transmitting at up to 50W with the new callsign.

Anyway, it transpires that the F140 amp, is wide band, in that it amplifies from 48mHz through to 700-800 odd. This is not ideal considering some of the HAM bands fall inside this range.

So a scout around, and some advice from 2W0ODS (Dale), I decided to pick up a PROception PROAMP104X distribution 4 way amplifier. £11.98 from a local supplier ToolStation. Keep in mind it doesn’t come with a 12v PSU. It has a frequency response of 470-862mHz, and has >= 26dB of rejection below 400mHz. The passband filter slopes from 400mHz at -26dB up to 470mHz at roughly +4dB.

Screen Shot 2016-01-04 at 16.13.42

A link to the UK distributor of the device can be seen HERE and includes links to manuals. You can get it cheaper from ToolStation though.

So, I returned home, installed the device in place of the old F140, F-type connections on both, so an easy swap over, and the existing 12v supply was in spec, so that was used.

I did some initial tests on 145.375 and the signal was maintained on various channels on the TV whilst I was keying, un-keying and talking. Another test made on 70cms to a local repeater GB3RT, and the TV picture was perfect.

Fingers crossed I have seen the last of this issue. One last option if it rears it’s ugly head is a ham band tvi filter on the input to the splitter, to further reduce unwanted signals.

Fingers crossed, and 73 !

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