[Hammarlund] HQ-170A info/help

[RAY FRIESS]

you have to remember that these receivers were used back in the days when the primary mode was AM.  The amount of drift you're seeing would not have
been objectionable back then, and in many cases probably not even noticable.   Yes, they include SSB reception capability, but that was not the primary use back then.
 
I have a 170A in my shack and I really like using it.   I also have a 145 in the shack.   The main way I reduce drift is just leave the thing on for long periods of time.  It
becomes more stable over time, but still drifts some.   And I had mine restored to factory specs by someone who knows his stuff.
 

 
> From: mskobier at charter.net
> To: Hammarlund at mailman.qth.net
> Date: Thu, 14 Apr 2011 21:15:50 -0700
> Subject: [Hammarlund] HQ-170A info/help
> 
> All,
> I am still trying to sort out my HQ-170A. I have read all the archives back to 2003, and plan on reading the rest as time permits. However, I have not been able to locate the specific information I need. I have been conduction various test on the receiver and have come to some interesting conclusions. I will try and list them briefly. 
> 
> The receiver still drifts. Not as much as it did before I replaced the 6C4. I will be replacing the first mixer as soon as the tubes arrive.
> 
> I have been making an attempt to measure the amount of drift on each of the bands. I have a very stable (PLL) Bontoon 103D Signal generator. I can set the frequency with a fair amount of accuracy, and it will stay where it is set. So I have been setting the frequency to mid band and tuning the receiver for a zero beat on the signal. I then let it stabilize for approx 15 minutes then adjust the output of the signal generator for zero beat with the receiver. I note the new frequency and come up with a drift number. Here are the preliminary results.
> 
> 1.9 mhz- No discernable drift
> 3.8mhz-approx 500hz increase in frequency
> 7.150 mhz- approx 300hz decrease in frequency
> 21.1mhz and up, the frequency drifts up and down in frequency by about 400hz. Not possible to get a stable reading.
> 
> I've also discovered that the receiver will drift in frequency if the line voltage changes. I do not have the cleanest power where I live. It is mostly stable, but it does vary as much as 10 volts throughout the day.
> 
> I know these receivers are known for drifting, but I am sure that someone has found a "fix" to eliminate or at least reduce the drift of these receivers. I have been studying the schematic trying to sort this issue out. Any help that you guys can give will be greatly appreciated. 
> 
> I almost forgot, I have not unplugged the receiver in over two weeks. So the VFO has had plenty of time to heat up. I still gave it one hour turned on before conducting these tests.
> 
> thanks
> Mitch KJ7JA
> 
> P.S. I love this Radio. It's way cool!
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