RADIO NOTES

Rotorua Morning Post, Volume 2, Issue 411, 21 December 1932, Page 6

RADIO NOTES

"Kathode.")

the week's jottings CIRCULAR IN REGARD TO IN STALLATION OF RADIOS AVERAGE WEEK'S RECEPTION

(Notes by

The past week has been an average one for reception. Fading and static have been present on most overseas transmissions, and local stations have suffered from fading and distortion. Last wealc it seemed that DX was coming hack, but on pr*eent indications, it is as far away as ever. KFI and KSL are not worth tuning in at present though they should soon increase in strength. Many listeners have received cireulars relating to installation of radio receivers. Care should he taken to sae that all transformers and metal liable to become alive are properly earthed and that all powel ieads comply with the regulations. Owners of superhetrodyne receivers should be careful not to touch the balancing eondenser screws located, in most cases, at the hack of the receiver. When once upset, it is almost impossible for the layman to bring the cireuits back to proper balance. Special apparatus and expert knowledge is required for this work. Notwithstanding the fact that most valves turned out by various makei's are more or less uniform, it is , not good praecice to use two or more makes of tubes in a receiver. In many cascs, sets are designed to work with one partieular brand of valve and a change to another make will upset the balance so necessary in modern receivers. The size of fixed condensers used in the usual grid-leak eondenser type I uetector circuit is not critieal. Usuali iy anything from .0001 to .0005 will [ be found suitabie though the winter | prefers .0001 for short wave and .00025 for broadcast reception, For j ii.-e in all wave sets, .00025 will prove n-iosi sauisfactory. It is a good plan to keep the aerial and lead-in wires pulled taut. Swayii'.g aeriais and leads in are frequent vaiises of ainionnal fading and mysterious noises. Unusual condiiions caused American stations to disappear, almost completely for several weelcs. Evidently uormal condiiions are approaching, as recent reports indicate that transI aeitic reception is rapidly improving. • Sniooth rcaction is essential in short wave receivers as it is almost ini].os:ible lo tune in long distance mlcphony wiih an unstabis detector. V.sta bility niay be traced to one or 1 ,v> of the i'ollowing eauses: — 1. Too high a value of grid leak. 2. Detector plate voltago too high. 3. The abscnee of or inefricient 011cration of a high frequency choke in , ie detector jdate circuit. 4. Too many turns 011 the tickler t oil. 5. In the case of a battery s^t, a i igh internal resistanee in oue or all ; f ihe battcries. (>. inci.rreet filament voltage. In most ca.-es Ihe cause will be iound in etihcr 2 ar.d S. A11 efiicient ( Iioke is es.-cntial, even if resistanee i oupling is used, as radio frequency 0 the audo crrcuits will make the joceiver unstahle and eause threshold 1'owl.