UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Quasi-Synchronous Demodulation

Synchrodyne · 15th Apr 2012, 3:04 am

Thanks very much, Ed. The SL624C was certainly a versatile IC.

I also had a vague recollection of the LM373 from the same era. For this, some data is available on the web. It was somewhat different, though, being a communications IF amplifier, which could be operated with agc (for AM and SSB) or in limiting mode (for FM) with AM, FM and SSB demodulators. There was a separate AM demodulator (of the rectifying type), and a multiplier that could be used as either an SSB demodulator (fed by an external BFO) or as an FM quadrature demodulator. But it is noted that it could be used as a synchronous demodulator. In this case I imagine that an external limiting amplifier would be required to provide a reference feed to the multiplier.

I have since found some additional useful references on the web, namely:

Prof. Tucker’s 1954 article at:

http://www.thevalvepage.com/radtech/synchro/synchro.htm

Pat Hawker’s 1972 Wireless World articles at:

http://www.epanorama.net/sff/Radio/C...0Part%201.pdf; and:

http://www.epanorama.net/sff/Radio/C...20Part%202.pdf

And the 1957 Costas paper:

http://www.costasarrays.org/costasre...ynchronous.pdf

Cheers,

15th Apr 2012, 3:04 am	#14
Synchrodyne Nonode Join Date: Jan 2009 Location: Papamoa Beach, Bay of Plenty, New Zealand Posts: 2,944	Re: Quasi-Synchronous Demodulation Thanks very much, Ed. The SL624C was certainly a versatile IC. I also had a vague recollection of the LM373 from the same era. For this, some data is available on the web. It was somewhat different, though, being a communications IF amplifier, which could be operated with agc (for AM and SSB) or in limiting mode (for FM) with AM, FM and SSB demodulators. There was a separate AM demodulator (of the rectifying type), and a multiplier that could be used as either an SSB demodulator (fed by an external BFO) or as an FM quadrature demodulator. But it is noted that it could be used as a synchronous demodulator. In this case I imagine that an external limiting amplifier would be required to provide a reference feed to the multiplier. I have since found some additional useful references on the web, namely: Prof. Tucker’s 1954 article at: http://www.thevalvepage.com/radtech/synchro/synchro.htm Pat Hawker’s 1972 Wireless World articles at: http://www.epanorama.net/sff/Radio/C...0Part%201.pdf; and: http://www.epanorama.net/sff/Radio/C...20Part%202.pdf And the 1957 Costas paper: http://www.costasarrays.org/costasre...ynchronous.pdf Cheers,