Overcoming Interference

Radio Record, Volume V, Issue 10, 18 September 1931, Page 29

Overcoming Interference

(To the Editor.) I AM in a very noisy area and am gur- ‘ younded by power lines-a DC subpower station 300 yards away and a hospital using electrical devices. The soil is rocky and volcanic. I have tried several earthing systems, but the more complicated they are the more noises they add to the set. However, I am trying out a device which appears to be quite effective. The precautions I have taken are:

1. The lead-in from the main "]" aerial is of armoured cable, and I used similar cable for the earth. I have found it better to use an earth consisting of an old copper caliphont, with zine sheets, ete. This is superior to pipes driven into the ground. The shielded portion of the aerial and earth system is taken to a separate earth, inerely angle iron driven into the ground.so that the noise collected cannot interfere with the set. I find that noise is reduced by 50 per cent. I tried connecting the armoured shielding of my earth wire to the water pipe, also to my set earth, but the noise increased. I have had to erect my mast 60 feet, ° so as to be above the power lines, and this has resulted in my set being broad, cue to the long down lead. I have had a great deal of trouble from noises from rotary converters, but by the addition of chokes and bypass condensers, With leads from the converter, of armoured cable, with the shielding earthed, again separately, I can overcome a great deal of the noise. Care must be taken that the shielding on the outside of the cable does not come in contact with the inside copper wire.