[Hammarlund] SP-600 IF Gain control

[k2cby at optonline.net]

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