[Premium-Rx] WTB: Watkins Johnson 8940 Tempest Rx System

Sat May 26 05:04:04 EDT 2018

 >It was a great spectrum processor but not the
>best receiver. 

The extraordinary low specified IP3 on HF of -10dBm (!) fits to your observations.
Other receiver models of WJ or other brands of that era used to have +30dBm at a similar noise figure,
Telefunken hat +40dBm.
-10dBm IP3 reminds me on my "retired" venerous HP141 spectrum analyzer system.

73
Clemens
DL4RAJ  


>-----Original Message-----
>From: premium-rx-bounces at mailman.qth.net 
>[mailto:premium-rx-bounces at mailman.qth.net] On Behalf Of 
>Watkins-johnson at terryo.org
>Sent: Saturday, May 26, 2018 8:23 AM
>To: Francesco Ledda
>Cc: 'Premium-Rx at mailman.qth.net'
>Subject: Re: [Premium-Rx] WTB: Watkins Johnson 8940 Tempest Rx System
>
>I rebuilt an 8999 with extender and some demod options.  It was
>interesting to play with.  (Replaced all thr tantalums after two
>successive failures damaged one power supply bus)  It is much more
>intuitive than the 8940.  It was a great spectrum processor but not the
>best receiver.  I sold the radio but still have a copy of the manual.
>
>Terry O'
>
>
>> The 8940 was replaced by the 8999.  The 8999, with the 
>optional extender,
>> goes up to 12.4GHz....
>>
>> Nice radio!
>>
>> -----Original Message-----
>> From: premium-rx-bounces at mailman.qth.net
>> [mailto:premium-rx-bounces at mailman.qth.net] On Behalf Of W2HX
>> Sent: Friday, May 25, 2018 7:29 AM
>> To: Watkins-johnson at terryo.org
>> Cc: Premium-Rx at mailman.qth.net
>> Subject: Re: [Premium-Rx] WTB: Watkins Johnson 8940 Tempest Rx System
>>
>> Fascinating. I would love to see a picture of this and know its basic
>> details like frequency range.  My other hobby is ruining 
>some PDP--11s so
>> i
>> wonder if this would be a cool system to acquire to combine 
>two interests
>> for me
>>
>> Eugene
>>
>> ________________________________________
>> From: Watkins-johnson at terryo.org <Watkins-johnson at terryo.org>
>> Sent: Friday, May 25, 2018 1:54 AM
>> To: W2HX
>> Cc: Jeff Kruth; ka2ivy at verizon.net; Premium-Rx at mailman.qth.net
>> Subject: Re: [Premium-Rx] WTB: Watkins Johnson  8940 Tempest 
>Rx System
>>
>> The 8940 is an interesting part of WJ history.  The first version was
>> produced under extreme duress.  Based on interviews I've done it was
>> pretty ineffectual, but satisfied the urgent contract under 
>which it was
>> developed.
>>
>> The A version, which was a major redesign, worked better.  
>It was designed
>> to work with a PDP-11 but they weren't a smooth coupling.  A 
>test engineer
>> for GTE who used one extensively on crypto machines told me he had to
>> reboot the PDP often because they would stop working 
>together.  I had one
>> of these with all the manuals and basically gave it away.  A 
>lot of space
>> and too much work for too little return.
>>
>> The B version worked out many of the kinks and expanded the 
>capabilities.
>> It worked well and was apparently well liked.  It still 
>leaves a lot to be
>> desired as a standalone receiver because it was also designed to be
>> computer controlled.
>>
>> The TSU and some modules of the B version were redeveloped 
>into another
>> receiver system as part of a larger contract with Iran but was never
>> delivered.  A multipoint monitoring system was also 
>developed for Germany
>> that was delivered.
>>
>> The 8940 was third wide spectrum analysis system that WJ 
>developed.  The
>> first two systems were even more cumbersome in size and operation.
>>
>> I have a lot of information on all of these systems and 
>iterations. My
>> websites are way behind my research because the digging is 
>going so well
>> that posting is way down the priority list.
>>
>> Terry O'
>> http://Watkins-Johnson.terryo.org
>> http://BlackRadios.terryo.org
>>
>>
>>> Sounds fascinating. Where can one findany photos of such a system?
>>> Google
>>> didn't help.
>>>
>>> Sent from Nine<http://www.9folders.com/>
>>> ________________________________
>>> From: Jeff Kruth via Premium-Rx <premium-rx at mailman.qth.net>
>>> Sent: Wednesday, May 23, 2018 4:35 AM
>>> To: ka2ivy at verizon.net; Premium-Rx at mailman.qth.net
>>> Subject: Re: [Premium-Rx] WTB: Watkins Johnson 8940 Tempest 
>Rx System
>>>
>>> Hi Bruce!
>>>
>>>
>>> I have two of them and would part with one.  They cost me a 
>bit back in
>>> the day. Complete system, desk and all, cables etc.  I may even have
>>> some
>>> documents for loan to copy. We can discuss the price. 
>Shipping would be
>>> by
>>> freight or you could pick it up.  These were functional units when I
>>> bought them, and have been in storage (in my lab) ever 
>since. Never got
>>> around to using them, so they have sat in the corner. Not many were
>>> made,
>>> and at one point WJ had a sale for one of mine to Denmark, 
>as WJ did not
>>> want to build a one-off. It was from this that I learned they were
>>> $300K.
>>> Did not come through. This was back just at the time the 
>Clinton Admin
>>> killed the Tempest requirement.
>>> They are really quite the thing!
>>>
>>> 73
>>> Jeff Kruth
>>> WA3ZKR
>>>
>>> In a message dated 5/22/2018 8:29:15 PM Eastern Standard Time,
>>> ka2ivy at verizon.net writes:
>>>
>>>
>>> I happened upon a brochure for the Watkins-Johnson WJ-8940 
>receiver in
>>>
>>> the desk console. Has anyone seen one of these, and even 
>more important,
>>> does anyone have a project one they are willing to part 
>with? It looks
>>> like a neat rig, restoring one would be quite a project but 
>that's the
>>> kind of puzzle and challenge I would like.
>>>
>>>  Bruce Gentry, KA2IVY
>>>
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>>
>>
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>>
>
>
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