[Hammarlund] Hammarlund HQ-170

[WQ9E at btsnetworks.net]

Mitch,

I believe in your first post you noted this was the A model of the HQ-170.  The HQ-170A has a separate filament transformer to keep the HFO (and I believe 1'st mixer) tubes always on as long as the receiver is plugged in.  If it continuously drifts 250 hz every three to four minutes AFTER 30 minutes or more of warmup I would first try a different 6C4 oscillator tube.  If this does not help then turn the dial to the low frequency end of the tuning range so that the capacitor is fully meshed.  Looking carefully straight down from above (to avoid parallax error) make sure that the rotor plates of the tuning cap are perfectly centered between the stator plates.  If this isn't centered it will affect drift performance.

You can find any of the bama materials on the edebris site:  http://bama.edebris.com/manuals/hammarlu/

If the worrisome drift is mostly on one band you could improve the performance by changes in the oscillator capacitors for that band.  But today it is going to be difficult to find the selection of various temperature compensated caps you are going to need in order to attack this issue.  You would be able to gain some additional control by using a variable trimmer cap in series with added compensation caps but then you run a high probability of decreasing mechanical stability.

Rodger WQ9E

----------------------------------------
From: "Mitch" <mskobier at charter.net>
Sent: Friday, April 08, 2011 11:43 PM
To: Hammarlund at mailman.qth.net
Subject: [Hammarlund] Hammarlund HQ-170 

I made an error in my first post. I posted that it drifted 25hz in 3-4 minutes. I should have wrote 250hz in 3-4 minutes.

Thanks
Mitch KJ7JA
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