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Re: [Discuss-gnuradio] OT: Looking for specifications for Watkins Johnso

From: Dave Emery
Subject: Re: [Discuss-gnuradio] OT: Looking for specifications for Watkins Johnson Radio Control Bus (RCB)
Date: Sun, 27 Apr 2003 00:58:43 -0400
User-agent: Mutt/1.4.1i

On Thu, Apr 24, 2003 at 12:04:54PM -0500, tongaloa wrote:
> I have a WJ receiver for 20-1200Mc which has a nice 21.4MHz IF out.
> Unfortunately, it's a 'panel less' receiver designed to work with
> an old DEC LSI 11 based controller via this thing WJ calls a
> Radio Control Bus. It would save me considerable work, if someone
> could point me toward the bus specification.

        Which WJ model number ?  I have some mid 90s WJ 8691A tuners for
that range that were once part of a Triggerfish FBI cellphone
surveillance system - they showed up on eBay a couple of years ago
demilled and missing some boards but the actual tuner modules are all
there.    The complete system used Analog Devices DSP chips to digitally
demod the IF for individual channels - 6 per portable box... with a two
channel front end tuner that converts a chunk of spectrum from 20-2000
mhz to a 70 mhz IF with a LO tunable in 100 hz steps derived from a
precision standard. Each of the six channels had a downconverter board
that produced I and Q for the Analog Devices DSP for that channel... and
a SCSI tape and disk drive to record the intercepts.  All controlled by
a laptop and fits in a medium size suitcase type carrying case complete
with pigtail type cell antennas.  But I just have the remains after
demilling - missing several parts, but useful as 20-2000 mhz to 70 mhz
wideband phase stable synthesized tuners.

        And I have read about (and vaguely remember seeing at Dayton)
some late 70s WJ tuners made for the Iranian Air Force (just before the
Shah fell) that definitely used a LSI 11 to control them.   There is a
guy on eBay who has been trying to sell one of these systems  and has or
had a page up showing pictures of all the gear that made up a system
(several racks of downconverters for various bands and a plasma display
driven by the LSI-11).

        But as you may realize if you have any serious experience with
"spook" and ECM electronics and surplus gear, 21.4 mhz is more or less
the standard narrowband IF for a whole host of 60s, 70s, and 80s
equipment. FWIW 160 mhz is more or less the standard for wideband (5-60
mhz or so) ECM and SIGINT tuners - pretty universal in the ECM world in
fact.  And very wideband military spread spectrum modems use 700 mhz IFs
as a standard.  70 and 140 mhz were pretty much the standard IF for
microwave links and satellite receivers and still many more or less
contemporary satellite modems put out and accept signals at 70 or 140
mhz to be upconverted/downconverted in the IDU/ODU combination to the
satellite frequency.   But the standard for IFs from antenna mounted
block downconverters for satellites is 950-1450, 950-1750, or 950-2100.

        And some spectrum analyzers put out 21.4 mhz IFs, with  a number
of recent ones (my two 90s era instruments for example) for some reason
switching to 10.7 mhz IFs.   Spectrum analyzers can be used as tuners
for sophisticated DSP demods, though of course this is more for onesy
experimentation than something that others can readily be expected to

        But given a WJ model number you might well be able to find
someone with a manual on the net somewhere.  There are lots of collectors
of this stuff and manuals do exist.  And worst case BAE Systems which
bought the remains of WJ apparently can supply some manuals at a price...
Of course the manual is likely to have bus pinouts and probably schematics
of the bus interface logic, but rather unlikely to include a detailed
engineering spec for the bus.

> Thanks,
> -bob
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://mail.gnu.org/mailman/listinfo/discuss-gnuradio

        Dave Emery N1PRE,  address@hidden  DIE Consulting, Weston, Mass 02493
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