[Hammarlund] SP-600 IF Gain control

[Les Locklear]

One particular item I didn't mention, was that being the R-320A/FRR was a J series and not a JX, it didn't have the crystal frequency control module, thus the IF gain knob was where the controls would usually be in place. It made for a very symmetrical front panel appearance.

Les

----- Original Message -----
From: <k2cby at optonline.net>
To: <hammarlund at mailman.qth.net>
Sent: 10/27/2017 2:57:05 PM
Subject: [Hammarlund] SP-600 IF Gain control
________________________________________________________________________________

One of the SP-600 military variants (R-320A/FRC) inserted a 5k pot (bypassed
with .01 caps) between the cathodes of the 1st and 2nd IF stages and ground
to serve as an IF Gain control.



Air Force T.O. 31R2-4-18-502 (May, 1956) makes a similar modification (but
affecting only the 1st IF stage) and requires that all SP-600-JX-17s held in
stock be modified. (Strangely, I don't recall ever seeing a JX-17 - probably
the most common SP-600 variant - that actually had the modification.)



What function was the R320A intended to perform - direction finding?
diversity RTTY? CW communications? AM communications?



Why was this feature included in the R-320A? Were JX-17s actually modified
this way, and did the modification actually improve performance? In what
application?



Miles, K2CBY





Miles B. Anderson, K2CBY
16 Round Pond Lane
Sag Harbor, New York 11963-3821
Phone: (631) 725-4400
FAX: (631) 725-2223

e-mail: k2cby at optimum.net





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