Look up the Collins CV-157. This 1950s unit converted the IF output of an R-390 receiver into upper and lower sidebands, which could be further demodulated by existing land line multiplexing techniques, such as 4 RTTY on each sideband. It heterodyned the R-390 IF to 100 KC and filtered that with a 10 CPS bandwidth filter. A mechanical servo tuned the heterodyne oscillator to hold 100 KC. It was a marvel of technology at the time. Didn't use the Knights filter, though. Possibly the heaviest converter Collins built. Had 44 tubes.
Had one once, but time passes. Bill Hawkins -----Original Message----- From: Joseph Gray Sent: Sunday, March 06, 2016 1:32 PM Assuming I made the pictures small enough, attached are two images of an very old crystal filter that a friend found. The strange thing about it is the bandwidth - 100 Hz. What could this have been used for, with such a narrow bandwidth? Joe Gray W5JG _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
