For that matter, has anybody on this board ever heard of the Beers FM receiver?
G. L. Beers was an engineer at RCA’s Camden facility when he developed a unique receiver. He described it in an article titled “A Frequency-Dividing Locked-In Oscillator Frequency Modulation Receiver” (Proceedings of the I.R.E., Dec. 1944, pp.730-737).
The basic Beers circuit used conventional front-end and IF stages, but the limiters were replaced by the "locked-in" oscillator, which produced a replica of received FM signal at 1/5 of the original intermediate frequency, and with one-fifth of the original frequency swing.
A pentagrid converter was used as the frequency-dividing oscillator, and its frequency was altered by the signal from the last IF stage, which operated much like the reactance tube in tube transmitter. The output level of the oscillator was constant, regardless of the level of the IF signal modulating it, making limiter stages unnecessary. The output was fed to a special discriminator designed for the lower frequency and smaller deviation.
The oscillator can only “lock in” to the incoming signal within a limited range -- the range of the channel. Its frequency cannot be shifted further. This was said to give the receiver extraordinary selectivity. The Beers circuit was also claimed to have extremely good rejection of impulse noise like the kind that a car ignition system without resistance wiring creates.
A more elaborate Beers circuit used a reactance tube driven by a compensated audio signal from the discriminator to alter the resonant frequency of a locked-in oscillator with an extremely narrow range -- too narrow to follow a conventional FM input signal on its own.
“The tube generally used in this circuit,” Beers wrote, “has been an A-5581, an experimental converter tube, which is similar to the 6SA7 but has a higher mutual conductance.” That’s noteworthy, because the transconductance of the tube was said to be one of the factors determining the maximum frequency swing that the oscillaor could follow.
Aside from Beers’ own article, the only other source of information on the Beers circuit I’ve ever found is in the book F-M Simplified by Milton S. Kiver. It’s in my second edition (1951), but was dropped from the third edition (1958). Kiver describes only the basic Beers circuit, using a 6SA7, and it’s in the chapter on detector circuits, not the one on commercial receivers.
So can anybody tell me whether Beers the circuit was ever used in a commercial receiver?
G. L. Beers was an engineer at RCA’s Camden facility when he developed a unique receiver. He described it in an article titled “A Frequency-Dividing Locked-In Oscillator Frequency Modulation Receiver” (Proceedings of the I.R.E., Dec. 1944, pp.730-737).
The basic Beers circuit used conventional front-end and IF stages, but the limiters were replaced by the "locked-in" oscillator, which produced a replica of received FM signal at 1/5 of the original intermediate frequency, and with one-fifth of the original frequency swing.
A pentagrid converter was used as the frequency-dividing oscillator, and its frequency was altered by the signal from the last IF stage, which operated much like the reactance tube in tube transmitter. The output level of the oscillator was constant, regardless of the level of the IF signal modulating it, making limiter stages unnecessary. The output was fed to a special discriminator designed for the lower frequency and smaller deviation.
The oscillator can only “lock in” to the incoming signal within a limited range -- the range of the channel. Its frequency cannot be shifted further. This was said to give the receiver extraordinary selectivity. The Beers circuit was also claimed to have extremely good rejection of impulse noise like the kind that a car ignition system without resistance wiring creates.
A more elaborate Beers circuit used a reactance tube driven by a compensated audio signal from the discriminator to alter the resonant frequency of a locked-in oscillator with an extremely narrow range -- too narrow to follow a conventional FM input signal on its own.
“The tube generally used in this circuit,” Beers wrote, “has been an A-5581, an experimental converter tube, which is similar to the 6SA7 but has a higher mutual conductance.” That’s noteworthy, because the transconductance of the tube was said to be one of the factors determining the maximum frequency swing that the oscillaor could follow.
Aside from Beers’ own article, the only other source of information on the Beers circuit I’ve ever found is in the book F-M Simplified by Milton S. Kiver. It’s in my second edition (1951), but was dropped from the third edition (1958). Kiver describes only the basic Beers circuit, using a 6SA7, and it’s in the chapter on detector circuits, not the one on commercial receivers.
So can anybody tell me whether Beers the circuit was ever used in a commercial receiver?