Hi All,
Thanks to Synchrodyne for the info on Redifon eqpt. in coast stations. I am impressed that you found this item. The Redifon eqpt. listed is new to me and will duly get added to my Redifon Equipment List.
Picking up on Radio Wrangler's comment about the use of SSB receivers for ISB reception, I would add further that most of the ISB circuits I have come across used fixed tuned receivers, generally with multi-channel capability, rather than their much more expensive fully tuneable cousins, Communications circuits of this type would generally be assigned 8 frequencies if duplex opoeration is required, 4 in each direction, 2 for Day use and 2 for Night use. These frequencies rarely changed once issued so the need for a fully tuneable receiver is not obvious.
As an example, the Redifon R499 receiver shared the same RF, IF and AGC circuitry as the R550 family of tuneable receivers, but was single conversion using dedicated RF coilpacks for each tuned frequency and the same IF block crystal filters as the big boys, With crystal controlled Local Oscillators and simple switched channel selection the receiver was very simple to remote control using Ledex motors to rotate the switch shafts. While not exactly "cheap as chips" these receivers would often be fitted up to 10 in a rack cabinet destined to spend their life in an un-manned receiving station, being remotely switched twice a day from Day frequency to Night frequency and vice versa.
The R499 supported the same ARU10 ISB Adapter as used by the R550 family so could be set up for ISB operation, or two receivers could be used to achieve the same end, Aviation ground -to-ground and HF ground-to-air circuits tended to separate receivers as they commonly used separate receivers for the Day and Night frequencies so that all frequencies were monitored all the time.
I would mention an earlier Redifon product introduced in thr early 60's. This was Rediplex, a packaged 6 RF channel, 4 speech channel ISB terminal with 100W RF output. All solid state except for the PA's, germanium transistors and based on the Weaver (3rd method) of SSB generation and demodulation. I know little of the Rediplex equipment but assume it was based on the Redifon GR410 transceiver which appeared at the same time and also used the Weaver method.
An advert for Rediplex appears on page 37 in:
http://www.americanradiohistory.com/...ld-1963-03.pdf
cheers
Peter G8BBZ