[Hammarlund] SP-600 IF Gain control

[Les Locklear]

Miles and Group,

The R-320A/FRR receiver (aka: SP-600J-4) included the if gain control and AVC and Diode output circuits. Engineering notes dated Nov. 8, 1951. The original Signal Corps. order no. was 19474 - Phila - 50-06. No other notes that would indicate a particular use, etc. were made.

Engineering notes state that if re-ordered, replacements would be based on the J-22 variant changes noted 2-13-1953.

Other than that, I have no additional information. Hammarlund as other manufacturers of that era made many running changes that were not annotated in ECN (Engineering Change Notes).

Les Locklear

----- 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





______________________________________________________________
Hammarlund mailing list
Home: http://mailman.qth.net/mailman/listinfo/hammarlund
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Hammarlund at mailman.qth.net

List Administrator: Duane Fischer, W8DBF
** For Assistance: dfischer at usol.com **


This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html