Wednesday 11 August 2010

Choked !

After a number of weeks of extra heavy noise on 20m, 40m, and 80m I decided to contact Ofcom. I sent an audio grab of the noise, and documented the frequencies that these high noise patterns were audible. Also in the email was a screen shot of HRD on frequency and S meter clearly being shown.

I’m not just talking a few S pints here, this noise was +20db making any reception a complete loss. Anyway a visit from Ofcom isolated the property, and probable cause of the noise, and after discussing with the owner of the faulty power supply all was good until....

Overall noise on all bands, though lower was up about S7 – S9. A discussion with my good friend Mat (G7FBD) highlighted a choke design commonly called an “Ugly Balun” Why it’s called this I have no idea, it’s not actually a Balun !. The principle is this, just wind 20ft of coax around a former – diameter not critical and place as close to your antenna as possible.

I was of course a little sceptical but with nothing to lose, I gave it a try. Surprising it did reduce the noise on all bands, but in particular on the 20m band. The jury is out whether it has also reduced the incoming signals, but for now I can receive the usual signals from Europe, and a couple of faint US signals too.

Anyway, here is the article I used when making the balun, I made mine with 20ft of RG58, and wound it over a ventilation pipe, held in place with Cable ties to keep tight and in place, i then fitted 2 PL259 plus each end and on 1 end added a SO-239 to SO-239 coupler to allow connection to the existing Coax.
Here is the article I used as a blueprint.

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