SHORT WAVE POINTS

Evening Star, Issue 22032, 18 May 1935, Page 4

SHORT WAVE POINTS

“ Microphonics ” or howling effects iii short wave receivers are not due to tho valves, but to direct vibration of condenser plates induced by strong sound waves from a loud speaker on top of the set or on the same table. With .sensitive receivers this truoble is likely to be quite annoying. t The simplest and most obvious remedy, of course, ii> to move the loud speaker. This does not always help, as the sound waves still strike the receiver. In obstinate cases it is helpful to damp the condenser rotor plates by fastening a piece of bus bar or other heavy wire across the outer edges. If the plates are brass, a couple of drops of solder will hold the wire; if of aluminium. sealing wax will do the_ trick. Experienced set builders rerognise the importance of non-microphonic condensers. and select instruments with short; rigid plates. USING A CONVERTER When a self-powered short wave converter is to be used with a broadcast receiver disconnect the aerial from the latter and connect it to the aerial post of the converter, connecting the ground post of tho broadcast receiver to the ground post of the converter. Next place the clip of the output wire from the converter to the open binding post of tho broadcast set. Then the tuning dial on the broadcast receiver should be set at the best frequency to use with the converter and loft there. This frqnency is always specified by the manufacturer of the converter.