[Exotics] Manual for Plantronics HF FSK 1280A modem wanted

[refmon]

Hi Dave,

I can help, I think.  I have a manual-I'm in the middle of a major shack
reorg, if I may have a day or two.  In the meanwhile, if you get a response
offering more immediate help, let me know.  By the way, I have 1 working
unit and a number of spare front panels...if you want to try a panel or two
let me know.

Regards

John Collins
Tualatin, Oregon
503 638 9002
_______________________
----- Original Message -----
From: "Dave Emery" <die@die.com>
To: <milsurplus@mailman.qth.net>
Cc: <exotics@mailman.qth.net>
Sent: Thursday, November 14, 2002 01:52 PM
Subject: [Exotics] Manual for Plantronics HF FSK 1280A modem wanted


>
> I acquired a couple of Plantronics/Frederick Electronics 1280A
> FSK converters (hf fsk modems) a few years ago and recently got
> interested in trying to make one work when a friend asked me about them.
>
> I have never been able to obtain a manual and schematics - does
> anyone know where I could find a manual or have one they would be
> willing to copy for me for expenses and a profit ?
>
> The 1280A is a somewhat modular tunable hf fsk modem circa the
> mid 80s implemented in through hole analog and digital IC technology
> using switched capacitor filters.  It allows independent tuning of both
> mark and space frequency in 0.5 hz steps from 300 hz to 6 khz and
> supports baud rates from 30 baud to 1200 baud with 6 different filter
> bandwidths.   It supports both AM type limiterless detection with
> threshold correction and detection on only mark or only space tones.  It
> also provides a mark hold squelch function and carrier detection.
>
> It will support both isochronous operation (synchronous) with a
> built in PLL that will lock on a synchronous bit stream and sample and
> regenerate the data, and also async start stop operation with sampling
> and regeneration of the start stop characters and apparently speed-up
> conversion and output of the data over a RS-232 port.   I believe one
> can also access the raw detected data unsampled and not re timed.
>
> It can be remote controlled over a 19.2 kb RS-232 port or from
> membrane switches on the front panel and has plasma displays of the mark
> and space frequency and baud rate and audio level in both mark and space
> channels.
>
> It also supports 2 channel diversity operation, either
> apparently by having two demod boards in one chassis or by tying two
> units together via back panel connectors.
>
> In the configuration I have, the units also include a transmit
> board that generates a high quality AFSK signal suitable for input to a
> SSB transmitter, so they can be used both to send and receive various HF
> FSK formats.
>
> Audio input and output is the standard balanced 600 ohms of most
> professional gear at the usual 0 dbm level.   Tone output level is
> adjustable.   Most of the other outputs appear to be RS-232, including
> carrier detect and request and clear to send...
>
> The units I have were probably NSA surplus, and I suspect
> generally optimized for high performance HF FSK monitoring.   Certainly
> Frederick Electronics was famous for FSK converters for that purpose
>
> --
> Dave Emery N1PRE,  die@die.com  DIE Consulting, Weston, Mass.
> PGP fingerprint = 2047/4D7B08D1 DE 6E E1 CC 1F 1D 96 E2  5D 27 BD B0 24 88
C3 18
>
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