Listen in Theres Lots to Hear.

NZ Truth, Issue 1103, 20 January 1927, Page 2

Listen m Theres Lots to Hear.

IS YOUR RECEIVER RADIATING ?

Noises and Some Methods of Elimination

(By "Crystal.")

Much has been written m the past about regenerative receivers but judging by the number of nightly howlers on the air m all parts of the country> there is, still a very large number of people who are "Entirely ignorant of its cause and how to prevent their own receivers from radiating. :-

REGENERATION, reaction,' howling, etc., are all one and the same and are caused by feeding- back a certain current from-.the detector valve to either the secondary circuit or the tuned anode circuit. This feedback when used judiciously adds greatly,, to the range and power of the receive, but, on the other hand/ if top much; regeneration Ms used it causes: howls and squeals which not only spoil' the. user's? reception-put also causes howling noises m every receiver over a very large area round about. . ■'-.'• .7 The first thing to be, done when a howling , noise is heard m your receiver is to make quite certain that it is 'not you that is causing ' the interference, this is done by out the following test. When a howl or moaning noise is alter your aerial tuning condenser, this being usually the left hand engraved dial looking at the set from the front M , '.'" ■ : ' y If the howl alters its note as the condenser is turned, you are the .offender, and steps should immediately be, taken tp "stop theT I'eceiver from howling, either by .loosening -the reaction or tickler coil by reducing the current from the high tension or "B" battery. ' The. above is one cause of interferenceTbut there is another type of interference which occurs just before the receiver reaches the "howling", stage, and,, j quite a number of people do not understand that a receiver has not necessarily' to be howling to cause interference. Howling is a noise at audio-fre« quericy due to violent regenei-ation, but this .other kind of interference is equally annoying, arid therefore,- if your reception is marred by a .noisy rushing sound, or the music is all distorted and "woolly." just moisten t the first finger and lightly touch the aerial terminal. y If your receiver is --radiating at all, a "click" or "plop" will be audible m the headphones, or loud speaker, and can 'be. remedied m the same manner as explained above for when the set is howling. ._■■ -A t-eceiver which is m a. radiating , condition is actually for the time being a miniature transmittei', and~will probably: interfere with hundreds of other listeners' within a radius of Aye miles from your home. . * It. is up to each "one of lis, there- \ fore, -to see that our receivers are not . radiating, as howls and squeals do not Usually- harmonize with the music. Single valve, and two valve receivers are 'the greatest cause of interference, andfcowners of this type of receiver ""; would pay very careful attentien^Rp the above article.

They also should only be content .to listen to some* near-by station and riot attempt to try and pick up the Australian stations, as this calls for a large amount of • regeneration and is almost certain to cause interference to neighbors who have probably a receiver i which has cost, far more than ' your own. „''A receiver which employs too much legeneratiqn will never give pure reception, the music or speech will b. •'woolly*' or "distorted." See that your "reaction" or "tickler' coil is of the correct size, and not r too large for the wave band upon wnich your receiver is operating. If you are using a No. 35 coil m the aerial secondary circuit, a coll of the same size or less should be used for reaction. Try using a little less "high tension" or "B" battery, current, this will result m many cases m an increase m signal strength, besides lessening 'the risk of causing interference. It should be noted that orystal receivers cannot radiate. Don't blame the other fellow before you have made sure that it is not your set tjiat is howling. ! Finally,., if all owners of valve receivers will only carry out the above suggestions they will be doing themselves and the whole of the listening-in community a great f avor which 'will help us all td.enjoy the broadcasting.