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Digital Radio in 1994, John Battison in 1931
Do you remember?
In 1994, the Electronic Industries Association's DAR Subcommittee and the National Radio Systems Committee's Digital Audio Broadcast Subcommittee began testing seven DAR systems at the National Aeronautics and Space Administration's Lewis Research Center in Cleveland. Following the labs tests, the committee made its recommendations to the FCC. This was the first time that several DAR systems had been subjected to laboratory testing.
Testing addressed the issues of sound quality, immunity to interference, transmission problems and IBOC compatibility with existing services.
The seven systems tested were: AT&T (in-band, adjacent-channel), AT&T/Amati Communications (IBOC), Thomson Consumer Electronics for Eureka-147/DAB (new band), USA Digital Radio FM Implementation No. 1 (IBOC), USA Digital Radio FM Implementation No. 2 (IBOC), USA Digital Radio AM (IBOC), and Voice of America/Jet Propulsion Lab (new band, direct broadcast satellite). Amati, Thomson/Eureka and VOA/JPS actually submitted two variants of their formats, so testing was administered on 10 systems.
In the end, the test results were inconclusive. USA Digital Radio, AT&T and the VOA filed protests with the EIA over the IBOC testing procedures because of the EIA's findings that IBOC showed poor performance. Due to these circumstances, follow-up field testing was conducted in San Francisco.
This photo was taken in 1931 in a wooden shack outside the house of Technical Editor John Battison. The transmitter had an oscillator, audio stage, RF stage and P.A. plate modulation. The tube filaments operated at 4Vdc with a B-plus supply of about 200V. The main supply was 230Vdc so no filament or power transformers could be used. The entire transmitter was 230V hot to ground. Battison, W8KUC and formerly G2AMC, built the transmitter himself, and operated it in the 180m band (160kHz).
In those days, engineers metered every conceivable tube electrode. The antenna was horizontal and about 50-feet long, using ceramic crossover spacers in the transmission line and was attached to a telephone pole and Battison's house. Ten watts was the maximum power allowed in those days without special dispensation. It was not stable and frequently broke into self-oscillation on the slightest provocation.
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