Radio today (Sept 1935-Dec 1936)

HIGH FIDELITY ON 1550 KC Successful experience of W2XR on 20-kc. channel. Commercial programs in the New York area. • COMPLAINT has often been made that the 10-kilocycle broadcast channels set up by the original Federal Radio Commission seriously bobble high-fidelity musical reproduction by limiting the side-bands to 5,000 cycles, or about the range of the piano keyboard. To provide experimental outlets for high-fidelity broadcasting, reproducing up to 10,000 cycles, the FCC a year or so ago established 20-kilocycle channels between 1,520 and 1,580 kc. One of the high-fidelity stations to be licensed on 1,550 kc. was W2XR, New York, which has now been operated a year under the direction of John V. L. Hogan, well known radio engineer. Increased volume range Experience with this station has revealed some interesting results. For example, tests of W2XR's transmissions have shown that they give definitely superior quality as compared with ordinary broadcasts, regardless of the type of receiver employed. An improvement over narrow range broadcasting can be noticed on all Pimeei'ingiii Wireless Pioneering in Urnaihastmg ■**-» Osietllst tales! TRUE FIDELITY STATIONW2XR Monday to Ep4ay . Hech week from ■/ to S p..m. . ... JBeginrthig Monday Nigftt,:Sept. i€ John Wanamaker New York i j Popular interest in hi-fidelity prompts sponsor to make W2XR a regular feature. model radios, according to a listener survey conducted recently in the New York area. Obviously, to hear the program as it is in the studio, it is necessary to use a high-fidelity receiver. True fidelity broadcasting, which means extending the range way down as well as up, allows for other improvements in art other than the flat frequency response. The dynamic range of sounds is greatly increased. It is possible to have a volume range of some 50 decibels. The average usable range in many instances is about 35 decibels, as compard to the maximum of 20 employed by most broadcasting stations. The range of volume actually usable in the home depends largely upon the noise-tosignal level and the output capabilities of the receiver. Low distortion A requirement of high fidelity that is often overlooked is that of low harmonic content or distortion. This applies to both the receivers and the transmitter. At W2XR the transmitter has been designed so that less than 1 per cent harmonic distortion is present at modulation levels up to 100 per cent, and the audio-frequency range is from 20 to 16,000 cycles. True fidelity broadcasting has been licensed by the Commission on frequencies of 1,530, 1,550 and 1,570. While the ground wave at these frequencies is attenuated rather rapidly, it is possible to have a higher radiation efficiency than at lower frequencies for same antenna heights, and the two effects practically cancel each other. The higher frequency more readily permits the use of a vertical quarter-wave radiator with its desirable features. Service revenue Fortunately, most of the receivers in use are able to receive these experimental broadcasts just above the broadcast band. A mail survey in the New York area disclosed that 80 per cent of the receivers could tune to 1,550. In Kansas City W9XBY declares that 98 per cent of the receivers can receive its program. W1XBS Checking high-frequency response with a variable-pitch whistle. in Waterbury, Conn., offered to adjust the receivers for a nominal fee so that they would tune to 1,600 kc, and now about 98 per cent of receivers within range can receive W1XBS. The migration of broadcasting to the 1, 500-1, 600's thus offers a new possibility for the serviceman. Adjustment of some of the older type sets to receive up to 1550 kc. is not too difficult and should produce a profitable income.* The phenomena of skip-distance at the higher frequencies is known to all radio men. For this reason duplication of stations on any one channel is to be avoided unless a great separation exists. If high-quality programs are to be enjoyed, the background must be free of the "hash" and whistles now found at night on some of the channels above 1,000 kc. Engineering difficult From the broadcasting point of view the transmissions are more difficult to engineer. The speech equipment must be very carefully designed. The studios represent a new problem. Echoes not ordinarily apparent are likely to show up with high-fidelity broadcasting. Non-directional microphones are used, and this involves a •John Rider discussed methods of increasing the frequency range of receivers in the Octoher issue of RADIO TODAY. See page 24. 18 Radio Today