Interference Elimination

Radio Record, Volume II, Issue 49, 21 June 1929, Page 30

Interference Elimination

I CONSTRUCTED the stalloy core transformer, wound to.give 180 . volts output. The results by test on a voltmeter drawing approximately 25 milliamps is 220 volts. Besides the ordinary primary and secondary windings, I put on a filament winding for the power valve and also a second filament winding and secondary tapped at every hundred turns to provide voltage for grid bias gear later o-. When I first connected the . ainator to the set, electrical interference was very bad, only very loud reception being possible, so that by reducing power to make the broadcast volume comfortable, the interference was reduced" Other set owner in the district cony plained of the same type of interference. We therefore arranged a set one night in a car with a loop aerial and went trouble tracking. The result was rather surprising, as instead of finding one source of interference we found many. After some discussion, etc., we came to the conclusion that in every case of interference it emanated from a house or building which did not have the water service inside the house, but merely a tap in the garden. We considered from this that the lighting circuit would be earthed merely on to a short pipe driven into the ground instead of as usual on the water mains, I may mention that quite a number of houses in this district are of the old type described above, having been rushed up in the hectic days of. the : dredging boom. Coupled with this is the fact that this is a very difficult district in which to obtain a satisfactory earth for any purpose. You will therefore. realise that interference is

very pr evalent..

R.

McINTYRE