[Premium-Rx] WJ Multi-Channel Receiver

[David I. Emery]

On Sun, May 25, 2008 at 06:03:38PM +0200, Francesco Clonfero wrote: 

>Hello to the group,
> I have a nice pristine conditions WJ-8890A/MCR  (MULTI-CHANNEL RECEIVER ) and
> I need any kind of information related to the specification and the possible
> use of this equipment.

	Would that instead be an 8690A ?

	There was a family of WJ 8690A and 8691A that was purchased by US 
intelligence and FBI folks in the mid 90s for old fashioned AMPS/NAMPS
analog cell phone intercept when used with special Windows laptop
software that as far as I know (the software that is) has never seen 
private hands.

	The radios themselves are powerful computer controlled (no front
panel) synthesized general purpose DSP based VHF/UHF receivers comparable in
performance and some features to a WJ miniceptor which can demod AM,
NBFM of various deviations, FSK, USB, LSB, and some PSK modulations on
up to 6 channels at once which can be located in two 30 Mhz chunks
anywhere from 20-1000 MHz and with a frequency extender from 1500-2300
MHz.

	They are capable of outputting the audio in analog form from two
channels, but also of dumping all 6 as telephone style digital PCM on a
special T1 interface and to a SCSI disk for recording.

	Few if almost any exist in private hands in complete and working
condition - quite a few were released "demilled" about 7-8 years ago
missing vital boards and parts and from time to time one of those or
others shows up on Ebay or at Dayton or other fleas.

	There are rumors a couple of collectors have one or more
complete and working, but like all rumors it is not clear if this is
apocryphal or not.  Certainly parts of them are in circulation and
show up at fests.

	I believe, but cannot prove it, that the FBI TRIGGERFISH system
mentioned in the late 90s NY Times bestseller "Takedown" about the
capture of Kevin Mitnick (by John Markoff) was one of these systems;
certainly the description of the device the FBI used to hunt down his
cell signal sounds remarkably similar if indeed it wasn't an 8691A and
laptop.

	There are two models, a rack mounted version consisting of a
separate tuner box and a IF/signal processing box (the 8690A) and a
portable suitcase or briefcase version with the same boards and tuner
packaged more tightly for mobile use in one chassis (the 8691A).

	Internally they contain two synthesized tuners that tune in 1
MHz steps and downconvert 20-1000 MHz to 70 Mhz (with the usual 10 MHz
reference and low phase noise).  NF on these is around 10 db or so,
typical of other WJ gear of that era.  BW on these is around 30 MHz... 
In addition there was an external downconverter (intended for INMARSAT I
believe) that downconverts 1500-2300 to feed the main downconverter
using the same 10 MHz reference allowing the unit to tune 1500-2300 as
well with similar phase noise and other specs.

	The IF box (or cards) contain tuners that tune +-15 MHz around
70 MHz (in 100 Hz steps if I remember correctly) and convert whatever
they see to I and Q for a DSP chip which does the actual demodulation.  
Apparently the usual configuration contained 6 of these DSP and
downconverter boards - switchable to the output of either downconverter
tuner under software control.

	The firmware for the DSP implements multiple BW's and detection
modes... the radio will go from quite narrow to wider than 30 KHz...

	Other boards in the box are housekeeping of various sorts and
bus interfaces for outputting the audio/data....
	
	Kind of an amusing relic, no longer of any use at all for cell
intercept (even if the software for the laptop was available, which it is
not) with analog cell having been  turned off (and analog INMARSAT long
gone too) but a very neat example of 90s SOTA spook gear and certainly
very usable as a computer controlled general purpose AM/FM/SSB/CW
VHF/UHF receiver capable of receiving multiple channels such as all the
channels of a trunking system at once.... or all the 2M  repeaters in an
area or other similar things.

	And I might add, as far as I know the units were not replaced
with more capable ones in at least FBI hands, but with the wiretaps
built into the switches (CALEA).   Rumor has it that little off the air
intercept is being done by law enforcement any more (the NSA is another
matter of course).

	Back to lurk mode...

-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."