RADIO NOTES

Rotorua Morning Post, Volume 2, Issue 344, 4 October 1932, Page 6

RADIO NOTES

TEST TRANSMISSIONS rotorua amateur station heard in europe ELECTRICAL INTERFERENCE (Notes by "Kathode.") An interesting article on electrical interference appears in the September issue of Q.S.T. The writer, Rupert R. Crum is owner and operator of amateur radio station W7ADF. He says: "I wonder if many know that a great deal of noise can come from J an electrical motor in operation that is not caused by dirty brush'es, bad commutator or grounds in the wiring of the motor and also the chokes and condensers in the country. One common source of such rtoise is a static charge built up on the motor frame by friction from belt slippag-e and also by induction from the motor field windings. To create a noise this charge may be leaking to ground through the motor base bolts by potential discharge or through a vibrating ground contact. Such a contact or vibrating ground may exist a good many feet from the actual motor location or may be in the conduit joints. of the | buiiding. wiring. It may leak to actual dirt ground through a floor or through water piping as far away , as the third floor of a buiiding. When looking for these grounds take all water piping and gas piping and even the stovepipe if one is around. The number of loose joints that can he found is surprising and at times to all appearance the offending pipe is not even close to an electrical cireuit. I know of one case where the

radio receiver in question gave an excellent imitation of Niagara Falls when the people in the neighbourhood drew a glass of water, yet the nearest house was at least 150 feet away. This was cured by moving the radio ground rod about four feet further out in the yard. To be noisy a conduit does not have to have a motor on the end of its service wires — all it needs is an electrical load. The heavier the load the worse: ;thei noise — usually conduit carrying higher voltages than normal is also more likely to cause noise; taking 110. volts as normal, 220 and 440 volt lines are proportionately worse offenders." In view of the fact that electrical interference is had in Rotorua, the above article may lead to some useful work being done by interested enthusiasts. i\t :I* The meeting of listeners held last Wednesday afternoon to discuss the establishment of a relay or B class station in Rotorua proved a little previous, as information of a vital nature was not available. Nevertheless, the meeting was mainly called to elect a committee and delegates to work in conjunction with th'e "Advance Rotorua" movement. This point was lost sight of at the meeting and it is hoped that something definite will be done along that line. * * * * When dry batteries run low they tend to become noisy. A two m.f.d. condenser across the terminals will usually cure the trouble though in bad eases it may be necessary to place radio frequency chokes in the high tension leads. * * * V The past week has been fair for reception, several new Ameriean stations coming over well. The YA stations have had fair strength though static has been present at odd times. * * * * Ameriean stations logged during the week were KMOX, KFI, KOA, KGO, KFRC and KOIN. The first three have being coming over with exeellent volume though fading was noticeahle on KOA and KMOX. :Jc A cheap and efficient radio frequency choke may be made by filling the slots of a glass insulator with fine wire. A screw or bolt passed through the end loops of the insulator serve to anchor the choke to the baseboard. ❖ # % ^ Conditions on short wave have been exceptionally good. The following Ameriean and Ilawaiian amateurs were logged on phone, with a two valve receiver: W6BVZ, California; W6AD, California; W6BKQ, California, and K6VAE, Hawaii. tj! SjC }{l During the international "Goodwill Tests" held hy the International Radio Transmitters' Union, one of -the local stations, ZLIBN was heard in Russia, Austria, Hungary, Spain, Poland, Great Britain and South Am'erica. These tests were held over two periods of seven days each though ZLIBN was only on the air for one hour on two different occasions. The power used was 65 watts and the wavalength, 42 metres. With this low power and short operating period IBN was second for the Auckland district during the first period and first for the same district during the second p'eriod. This demonstrates the suitability of Rotorua as a transmitting araa though of course, it is probable that tests may reveal even better areas in other parts of the district.