Radio Broadcasting Transmitters and Related Transmission Phenomena

HE radio t r a n s m i t t e r is essentially a focal point in t h e presentd a y broadcasting system, since upon it t h e program circuits converge and from it t h e radio distribution network e m a n a t e s . For this reason, the requirements which have been imposed on transmitting a p p a r a t u s are extremely rigorous, and all phases of transmitter performance have been subjected to the most careful scrutiny. Under these stimulating influences, the last few years have brought a b o u t some very n o t e w o r t h y advances in this portion of the broadcasting field. As long as music and e n t e r t a i n m e n t continue to hold a prominent place on broadcasting programs, fidelity of transmission will probably remain t h e most sought-for characteristic, not only for t h e radio t r a n s m i t t e r itself, b u t for all of t h e a p p a r a t u s units in the system. A very high s t a n d a r d of performance has now been a t t a i n e d in this respect. Fig. 1, below, shows the overall frequency-response characteristic of a new t y p e 50-kw. e q u i p m e n t , the first of which has gone into service at one of the leading American broadcasting stations within t h e past few months. It will be noted t h a t this characteristic is substantially flat between 30 and 10,000 cycles. T h e greatest d e p a r t u r e from t h e horizontal line which is t h e ideal characteristic is less t h a n 1 d b . T h e frequency discrimination which this represents is of such a low order t h a t it probably could not be detected in ordin a r y listening tests, even by a skilled musician.