[Hammarlund] New to Hammarlunds

[Glen Zook]

Welcome to Hammarlund receivers.  Although some people will disagree, the Hammarlunds are notorious for drifting, especially on the 20-meter band and higher frequencies.  The series that started with the HQ-120X, then HQ-129X, then HQ-140X, and finally the HQ-150 are generally very stable after about a 30 minute warm up.  Unfortunately, the HQ-100, HQ-110 series, HQ-160, HQ-170 series, and HQ-80 series are all known to drift.

Now, there are individual receivers within any of the models that drift considerably less than average.  Unfortunately, those receivers are not that common.

The main BAMA site has not been active for quite some time.  However, the mirror site is working quite well.  It is at

http://bama.edebris.com/manuals/

Glen, K9STH

Website:  http://k9sth.com


--- On Fri, 4/8/11, Mitch <mskobier at charter.net> wrote:

I have been a ham for a little over 25 years. I first became interested in radio when I was given an old Halicrafters S-38 when I was about 10-12 years old. I fondly remember staying up late listening to broadcasts from all over the world on that old thing. 
 
I have recently decided I wanted to put together a vintage transmitterr/receiver setup. I already have a Heathkit DX-60 and matching GH-10B VFO I aquired some 15+ years ago. I took a chance and purchased an Hammarlund HQ-170A off of Ebay to go along with it. Once it arrived, the first thing I did was replace the hard broken off electrical cord. I replaced it with a three prong grounded plug. Tying the ground wire to the chasis. I then removed all the tubes, cleaned the chasis of years of accumulated grime, then brought the power up via a variac slowly over the period of several hours. No smoke! I reinstalled the tubes and applied power. the receiver came to life with a hiss, then I spent the next several hours tuning in various SSB signals across the spectrum. This thing is really sensitive and it easily can tune in on one signal on a crowed band. Needless to say, I am quite impressed with this receiver.
 
There is one issue with the receiver. Even after giving it an extended warm up (days), it drifts quite noticeably. Making some crude comparision test with my IC-756PRO, the 170 drifts about 25hz in 3-4 minutes. Primarily it is drifting upwards in frequency. This is on the 80m band. 20m doesn't appear to drift quite as bad. It does drift, though. In my research on the internet, there appears to be a fix for this drift. However, the BAMA archive, where this information is rumored to be located has been down for several months, and I can not seem to find the necessary information anywhere on the net. Does anyone on this group have the particular information on how to fix or at least reduce the drift issue with this receiver? It also appears from my research that the issue is caused by a couple of temp compensating capacitors. The question is which ones, and what temp coefficient capacitor do I replace them with? I have the manual for the radio with
 schematic. In studing the parts list and schematic, it appears there are only about 5 or 6 capacitors that could possibly be the cause. Of course which one(s) is the question.