[Hammarlund] HQ-180 AVC

[Byron Tatum]

Hello-
    The gentleman that gave me my novice test in the late 1960's had the HQ-180 
/ HX-50 combo. I had only read about this gear in the brochures I received from 
Hammarlund, but a receiver such as the HQ-180 was way out of my yard mowing 
budget. I was amazed at the operation of that receiver back then. Finally, I 
aquired a very nice HQ-180 and plan to set up a vintage station similiar to that 
one.
    I have been checking out the HQ-180 recently (around 1350 SN). One thing I 
have been studying is the published AVC improvements by Dallas Lankford. I went 
ahead and bridged R-23 (1 meg) in my set and it made a worthwhile improvement, 
eliminating the "pop" at the start of AVC action on a stronger signal. Next I 
did the other portion of the AVC improvement and placed a 0.47 uFD mylar cap in 
parallel with C-131, increasing the decay time in SLOW AVC position the about 2 
seconds. This gave a worthwhile improvement when listening to SSB.
    It seems to me I detect a slight pulling of the receive frequency when 
listening to strong signals. I read about someone removing the AVC from the 455 
KC to 60 KC converter tube, as this was the source of the pulling. Can anyone 
shed any light on this? Does anyone have a description of how this 
modification should be done?
    Also, are there any other desirable improvements to this fine old receiver?
                                    Thanks, 
                                        Byron WA5THJ