[ICOM] SSB Compression

[Adam Farson]

To answer WB2CPN's question: COMP affects the transmitter only, not the
receiver.

Clete, from my experience in Intelsat satellite communications in the
1970's, all Intelsat telephone/data links were FDM/FM. An FDM
(frequency-division multiplex) baseband modulated an FM uplink exciter,
which drove a TWT or klystron  HPA. At the receiver, a phase-lock
demodulator recovered the baseband and fed it to an FDM carrier system for
handover to the terrestrial network. Companding was generally not used on
these circuits, but echo-suppression (and echo-cancellation) were always
required because of the 600mS round-trip delay.

Companding systems such as the British Lincompex were used on transatlantic
HF-ISB common-carrier circuits. There is a discussion of this in "HF Radio
Systems & Circuits"  , Sabin & Schoenike, editors. Noble, 1998, pp. 271-290,

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of C Whitaker
Sent: 05 July 2005 17:31
To: ICOM Reflector
Subject: Re: [ICOM] SSB Compression

de WB2CPN                   2005.07.05

When I turn the COMP on does it also expand
the incomming SSB?   Re 706MkIIG and 756ProII.

Not exactly ICOM info, but Compandered SSB was the primary mode of some of
the trans-Atlantic satellite circuits some 15 or 20 years ago.  Adam knows
more about that than I do.  Anyway, the advantages of compressed/expanded
SSB depends heavily upon the algorithm used, which is up to here in
legalities.

73  Clete





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