[Premium-Rx] Watkins Johnson WJ8690A/MCR

[Berndt Josef Wulf]

G'day David,

many thanks for a very comprehensive description of this receiver. It surely 
sports some very impressive features. From your notes I take it that this 
receiver was only a very small part of a much larger system.

AFAIK, my receiver only covers the 25-1100MHz spectrum. The intentions are to 
use it for amateur radio astronomy and to monitor VHF/UHF HAM-radio repeaters. 
As such, I only need frequency, mode, bandwidth, PREAMP/ATT and AGC control - 
anything else would be a bonus. Has anyone managed to control this receiver to 
some extend using a PC? If so, I would love to hear from you. 

73, Berndt
VK5ABN


>On 04/07/10 David I. Emery wrote:
>On Sun, Jul 04, 2010 at 12:46:49PM +0930, Berndt Josef Wulf wrote:
>> G'day,
>> 
>> I would be grateful for any information on above receiver. 
>
>	It is a early 90s FM, AM, USB, LSB, FSK, CW, DQPSK computer
>controlled (no front panel)  VHF/UHF six channel receiver that tunes
>from 25-1100 MHz and 1500-2300 MHz in 100 Hz steps. 
>
>	Consists of a 70 MHz IF and controller  box (8690A/MCT) and a
>separate dual channel tuner box (8690A/DCT) - with two separate
>tuners/70 MHz downconverters in it that allow any two 25 MHz segments of
>spectrum (in 1 MHz steps) from 25-1100 MHz to be input to any of the 6
>70 MHz channel tuners.
>
>	The individual tuners each have a 25 KHz roofing filter and DSP
>based demods (two DSPs per channel) that implement further selectivity
>and the actual demodulation of the signal.   Bandwidth ranges from
>hundreds of Hz up to 20+ Khz...
>
>	Control of this is via a PC/laptop  using either ethernet or a
>serial port...
>
>	Depending on the cards installed audio output is analog or
>digital in a couple of formats (T1/E1 and a proprietary WJ parallel bus
>are supported, plus SCSI).
>
>	These receivers were originally designed mostly for intercept of
>old fashioned (and almost entirely no longer in use) ANALOG FM 
>cellphone and INMARSAT traffic, but they are completely general purpose
>receivers and can be used for receiving normal NBFM, SSB  and AM signals
>in the VHF/UHF spectrum and with some DSP upgrade, also P25 and other
>narrow band digital public safety and ham band signals - each receiver
>being capable of simultaneously capturing 6 signals all at once.
>
>	Some have shown up on Ebay over the years, but unless you have
>BOTH the dual channel tuner box AND the 70 MHz receiver box proper it
>isn't a complete system and much less useful.   And there are also
>1500-2300 downconverter boxes and preamps and other accessories around
>as well.
>	
>	And a sister repackaged version exists, the 8691A,  which uses
>the same modules but all packed into an all in one  mobile version (not
>the rack mounted 8690A with two components) with the tuners mounted
>inside the main box.
>
>	Very little documentation (and no WJ software) exists in private
>hands for these things... but it is possible to make them work as general
>purpose VHF/UHF receivers if one is willing to do some reverse engineering.
>And analog cell (and INMARSAT) is dead, so there isn't much one can do
>with them for that any more.
>
>	The dual channel tuner is actually a respectable low phase noise
>high dynamic range external 10 MHz reference 25-1100 MHz to 70 MHz
>downconverter BTW... and can be used with other DSP hardware capable of
>handling a 70 MHz IF input... 
>
>	There are a few WJ collector types around who have some of these
>systems from Ebay - either complete or not... and they are a fairly neat
>and somewhat more modern than some WJ radio...
>
>	Subsequent 869x generations converted to VME or VXI cards and fancy
>FPGA I and Q demod chips... those, I suspect, are less useful.
>
>
>-- 
>  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."
>