[Hammarlund] SP-600 Squelch Attachment

[Glen Zook]

The crystal controlled SP-600 receivers were often used for fixed RTTY operation.  Having the audio squelched when a signal was not being received would accomplish several things including less noise in the operating room and no random letters, etc., caused by noise.

Glen, K9STH 
Website: https://k9sth.net 

    On Saturday, January 18, 2020, 01:20:57 PM CST, k2cby at optonline.net <k2cby at optonline.net> wrote:  
 
 This is a new one on me, but I can't imagine anybody using (or needing) it
on the HF bands. Maybe 30 to 54 MHz AM?

I did note that the kit originally included a skirted dial. I wonder what
happened to that and whether it just duplicated the AF gain knob.