[Hammarlund] HQ-129x IF alignment

Fri Aug 24 11:31:48 EDT 2012

Hmmm, I bought a HQ-129X used in 1956 thru an ad on the wall at Harrison 
Radio in NYC, I lived on LI back then. It had the calibrator factory 
installed according to the 1953 BOS that was included making it one of the 
last runs before the 140.

The switch was in the same position but no added label.

Ive not seen another like it and it would be something if yours is the same 
one. I sold it in 1968 or so and shipped to Indiana from NH.

Carl
KM1H

----- Original Message ----- 
From: "William A Kulze" <wak9 at cornell.edu>
To: <Hammarlund at mailman.qth.net>
Sent: Friday, August 24, 2012 10:31 AM
Subject: [Hammarlund] HQ-129x IF alignment

>A while back I was talking about utilizing an sdr as a visual aid for 
>getting a balanced passband in the IF. My original idea was to use the 
>panadapter to see the shape of the filter. Well, that didn't work out 
>because where you measure the output, it's the neg dc at the detector. (it 
>works like WOW feeding it with the IF out of a 390a!)
>
> Anyway, lacking a sweep generator, I sent the signal from the URM-25F to 
> both the SDR tuned at 455kc (basically doubling as a freq counter) and the 
> injection points for each stage, as I went. I monitored pin 5 of the 6H6 
> with a scope. I peaked everything at 455kc and then went above and below 
> center freq until I reduced the neg DC level on the scope by half. When 
> all I did was peak at 455, I noticed the peak was not in the center of the 
> passband, or if it was, the +/- 3kc were not equal . And if all I did was 
> peak at 455 I wouldn't realize that without sweeping the generator through 
> the passband.
>
> So I played around with the cores until I had the peak at 455kc and the 
> +/- 3 kc points balanced.
>
> When I did the part where you figure out what the xtal freq is, it seemed 
> like it was resonant at 453kHz, if I did it right. (does that raise a flag 
> for anybody?)  So I tuned the whole IF strip at that peak and what a 
> difference it made.
>
> When I did the LO adjustments I didn't even inject a signal from the 
> generator. I used a sniffer coil connected to the sdr, figured out the 
> dial freq plus 453kc (or minus on the top two bands) and set the sdr to 
> that and adjusted the LO, using the panadapter on the winradio to see when 
> I was right on freq. I used the generator to then adjust the RF sections.
>
> I still have linearity issues on the dial, though. The ends are right on 
> but it's off in the middle.
>
> Another way the sdr came in handy, though, was I could highlight its 
> bandpass, say at 6kc, and quickly see when I was on freq at +/- 3kc and 
> then adjusting for a balanced shape to each stage of the IF on the 
> o-scope.
>
> I must say, it's quite the Rube Goldberg setup, but I was able to do this 
> with what I had on hand.
>
> The audio has a much better sound, that off-center peak was giving it a 
> brassy sound and it was hard to feel the station center when tuning. On 
> ssb it was more stable than I thought it would be, and the xtal filter 
> seems to work well. Nice and clear with low noise, but I think one big 
> reason some of the older rigs sound good on ssb is that you have the agc 
> off, so it doesn't bring up the background noise in the quiet spots like 
> with the agc on.
>
> I've recapped (paper and electrolytic) the radio (from hayseed hamfest, 
> btw) and replaced some out of tolerance resistors, but not all resistors 
> or the mica caps.
>
> Oh, BTW, the serial number on the back of the chassis is like 2435, or 
> there about, I'm not where the radio is at the moment. I am told I am the 
> 3rd owner. It is an early model with red 'make and model' lettering and 
> original chickenheads, except one that I broke!   8(     It has the 
> hammarlund 100kc xtal marker installed with a switch in the lower left 
> corner of the front panel, an adhesive metallic label attached above it. I 
> also have a jpeg I got online of a qsl card my father had sent out in May 
> of 1946 and it says he was using an HQ-129x. Must have been right when 
> they came out!
>
> There's a picture on my QRZ page from last winter. The shack pictures are 
> due for an update, though. Maybe this weekend. It's nice to have a 
> workbench after a long period without one. This was my first real re-cap 
> job and it's given me some confidence to tackle the other radios I have. I 
> might even clean up the gear train in my R-390a!
>
> Bill Kulze W2NVD
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