RADIO NOTES

Rotorua Morning Post, Volume 1, Issue 79, 24 November 1931, Page 7

RADIO NOTES

"Kathode."

By

, .During the International programme from 1YA this evening, Mrs. Gordon Robertson will ' lecture on "Music — A National and International Art." The programme from 2YA to-night j will be of the popular type. The Salon Orcestra "will play "Mireille," "Jevington Suite," "Chanson Indoue" and "Minuet," and several latest da,nce numbers. The major portion of the vocal items will be given by the Melodie Four. Also on this programme will be Mr. Charles Pengilly (contralto), a newcomer to 2YA. A Scotish concert to commemorate St. Aridrew's Day will be broadcast from 4YA this evening. Reception durirg the past week has not been good in Rotorua. Static and wealc signals have been evident on most nights and the Australian stations have been very much' below average strength. The American s'tations "were not as good as u'sual, though KFI continues to be heard during early evening hours. The a.c. type of pentode valve is rapidly becoming' , popular and there is every •indication that they- will ^OQn be universally used .as an output tube. ' The blue glow seen in most pentodes is evidence of good quality and should not be mistaken for poor quality as in the case of the thfe'e element valve. This phenomenon is not gas, but a -fcathode. ray bombardment of the glass. This condition is only present in tubes. .which are gas-free. The blue glow is caused by the electrons passing through the grid and receiving acceleration from the plate," then striking the glass and causing the deposits there to fluoresce. Several local experimenters have installed shielded lead-in wires from their aerials to receivers for. the purpose of reducing local interference. In localties where interference is bad this experiment is worth a trial. The entire down lead is composed of lead-covered cable and the sheathing is earthed. No doubt a reduction in, signal strength wouid be noticed, but a reduction of interference pickup would more than compensate for a small loss in volume., . In . cases where there is too much loss of volume, the shielding could be left unearthed, or, better still, earthed through a fixed condenser. The effect of grounding would increase with the increase in capacity of the condenser, therefore to avoid too much loss in signal strength, a small capacity should be tried first. Kathode would suggest a .0001 or .00025mfd as being a good value. The purpose of this column is to be of use and instruction to "Morning Post" readers. Questions addressed to "Kathode," care of this paper, will be answered each week. In a request for information, include any data that wilLbe of assistance and limit the number of questions to not more than three. Short wave reception during the past week has been up to average. The Siberian station on 70 metres is coming in well just now and is always at loud speaker volume. A new short wave station in Honolulu was heard testing with New York several days ago and judging by the volume then received good reception should be experienced in Rotorua. The station operates on about 51 metres. G5SW, Chelmsford, England, was heard at 'good streilgth, though a strong surge was evident. A powerful short wave transmitter is to be constructed in England almost immeaiately. The purpose of this transmitter is to provide programnies for the Dominions, and when it commences, relays from our lpcal stations will be a regular feature. A short wave received will not be required, as the programnies from England will be re-broadcast on the usual long wave band. Several wavelengths will be used for the short wave transmissions, so that they may be received at almost any hour of the day. In 1927 there were over 700 broadcasting stations in U.S.A. The interference problem becanie acute and the number of stations has been reduced to just over 600. To get some idea of what the! hetrodyhe type of interT ference must have been, one has only to listen on good nights to dozens of New Zealand and Australian "B" class stations jamming each other on the lower end of the broadcast band. Some system of co-operation should exist between the New Zealand and Australian authorities when licensing "B" class stations. Most a.c. receivers are equipped with • some type of hum-balancer. In many cases this takes the form of. a small potentiometer located somewhere on the chassis. If hum is too prevalent it is a simple rnatter to adjust the balancer by turning it slightly to tfie right or left. In cases ydiere therd is some doubt as to where the eontrol is located, someone who has some knowledge cf receivers should inspect the set.