NOISES IN RECEIVERS

Evening Post, Volume 137, Issue CXI, 10 June 1926, Page 14

NOISES IN RECEIVERS

A large percentage of the trouble experienced with radio receiving sets by the average broadcast listener may be traced directly to little things that go wrong with the movable parts of a set, writes "Thermion," in the "New Zealand Herald." The variable condenser valve socket and rheostat are concrete examples of this statement. From the first of radio, trouble has been experienced with poor contacts in these instruments. Poor volume, noisy reception, and fading signals are frequently caused by defects in these pieces of apparatus, and not by external interference. English valve sockets give rise to no trouble if the split valve legs are spread well apart, but in the American sockets the effect is most apparent. ' Most .sockets employ springs of phosphor bronze, designed to bend upward and make contact with the soldered end , of the valve legs. ' There are two things which may cause noise with this arrangement. First, the solder on the tip of the valve legs may coat the contact spring with load oxide (a poor conductor of electricity), making, -a high resistance electrical connection. Second, the spring loses its resiliency and fails to supply sufficient pressure against the valve legs to give a good electrical, contact. The first of these difficulties can be corrected by filing clean the spring contacts of th.3 valve socket. To overcome the second, bending the contact springs back to their original position may be tried, although it is tho writer's experience that the best cure is a new valve socket. Condensers should always have a "pigtail" connoction between the rotor plates and their terminal. Rheostats cause trouble when the wire or contact spring becomes dirty or corroded, and when the contact spring loses its tension. Both of these difficulties may bo located by an examination of tho instruments, and are easy to correct.