Information Wanted - Nems Clarke SDU 300-6 Spectral Display

[Chuck WB3LGG]

Hi All...
I have a Nems Clarke Spectral Display Unit Model SDU 300-6 that I would like to get information on.  I'm looking for a manual, schematics, and any thing else.  Copies are fine and I'd gladly pay reasonable costs for same.
I have powered it up and it appears to work .  I'm not sure what the IF frequency is but it seems to show a spetral display when connected to the IF output of my 75a-4.
Any help or leads are appreciated....
Chuck Kembring     WB3LGG
Cochranville, Pa.

[WA1GFZ]

Chuck pump a signal generator into it to see what it tunes. Run -20 DBM.
There are some small CRTs on WJ epay if tube weak.

[Steve - WB3HUZ]

Ah yes, Nems Clarke. Now there is a name I haven't heard in a long time. They made some pretty nice receivers in the 50's and 60's. Some of their designers later went to work for CEI which later became Watkins-Johnson (WJ). Ever notice how much the CEI 901 looked like the Nems Clarke units?

I'm not familiar with this unit. But if it was designed to be used with the Nems Clarke receivers like the 1906, 1907 and 2801, it probably wants to see 21.4 MHz for an input, as this was the main IF for these receivers.

[Chuck WB3LGG]

Thanks 'GFZ and 'HUZ....
I have powered up the unit and it has a nice bright display and the controls seem to function normally.  I have injected signal into it and get results in many places.
My preliminary search for info  told me that my unit (3 Mhz Bandwidth)was similar to a SDU-200-6 (2 Mhz Bandwidth) which was designed for a 1306B receiver which I cannot find anything on either.  I do see an IF listed as 21.4 as you stated Steve.
When I connected it to the 455 Khz IF out tap (last IF of the 75A-4) I get a spectral display that looks promising but quite a bit off of the 21.4 Mhz this unit may REALLY want to see.
Some documentation would really be nice.....
Thanks,
Chuck

[Steve - WB3HUZ]

I'd bet money it's not 455 kHz. Most of these units had IFs of 21.4 or 30 MHz. If you get a new one (not necessarily Nems Clarke), from the late 70s and 80s you'll start to see 70 MHz IFs.

[WA1GFZ]

yup most of that stuff was 21.4. It would be easy to up convert 455 to 21.4 with a crystal oscillator and double balanced mixer.