[ARC5] Radios and the Canal - Hammarlunds

[Kenneth G. Gordon]

> I had a HQ145X and when I got it it drifted so much it was really
> useless for CW or SSB and almost useless for AM! I found that the HFO
> was the drifting part but the tube tested good. I subbed in several
> others I had and the VFO settled right down!

Yes. Hammarlund used the 6C4 HFO in almost all of their models after the 
HQ-129X.

My HQ-110C drifted like mad until I subbed a few 6C4WAs and finally some 
of the military ruggedized versions that had a number like "6139" or 
something. Then it settled right down. I also subbed the 6BE6 first mixer tube 
for a mil version, and THAT helped too.

Concerning the earlier versions: I had a brand new BC-779 back in the day. 
It drifted quite a bit until it was well warmed up.

Like Todd mentioned, the manual flatly states that it needs to be well 
warmed up. I never turned mine off in fact, and had it mounted in a rack.

As I have mentioned before, I added a triode product detector to it and used 
it extensively for several years for RTTY on 20 meters and below.

On 20 meters, when listening to a weak steady carrier, it drifted 
back-and-forth a few cycles all the time. It was actually very pleasant to hear 
and never interefered with reception.

Hammarlund brought out a service bulletin after WWII sometime, I don't 
know the date: that was a factory recommendation that one add a 3 pfd 
N-750 temperature compensating capacitor to the HFO capacitor which 
would drop the warm-up drift to very low. I never did that though.

Maybe when I restore one of the three BC-779s I have here, I'll try it.

Adding a BC-453 "Q-5er" makes those receivers really handy for CW and 
RTTY, BTW.

Ken W7EKB