[Hammarlund] HQ-129-X Serial Numbers

Tue Aug 14 16:43:23 EDT 2012

Having a separate general coverage shortwave receiver 
is a wonderful maintenance tool for doing alignments of 
other receivers. Tune your general coverage receiver to 
a frequency that is above or below the desired frequency 
by the I.F. frequency and see where the local oscillator 
of the unit under test falls. 

Virtually all boat anchor receivers use local oscillator 
BELOW operating frequency for frequencies from about 
10 MHz and higher. The reason for this is that builders 
could get better frequency stability at lower frequencies. 

For operating frequencies below 10 MHz, the oscillator 
stability is not such a problem and running the L.O. 
above operating frequency also gives marginally better 
image rejection. 

"Normally" alignment is done with bandspread capacitor 
nearly open AFTER the cap is set to fully closed with the 
tuning dial at the low end; zero for bandspread dials that 
simply read 0 to 100 and a calibration mark at the low 
frequency end for bandspread dials that are "calibrated." 

It is also "generally" customary that the "main" tuning dial 
should be set at the lowest frequency with the main tuning 
capacitor at full mesh. 

* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* k2gkk at hotmail.com *  
* Oklahoma City, OK * 
* USAF, Ret (61-81) * 
* * * * * * * * * * * 

> From: kgordon2006 at frontier.com
> To: 1oldlens1 at ix.netcom.com
> Date: Tue, 14 Aug 2012 20:10:55 +0000
> CC: Hammarlund at mailman.qth.net
> Subject: Re: [Hammarlund] HQ-129-X Serial Numbers
> 
> On 14 Aug 2012 at 11:05, Richard Knoppow wrote:
> 
> > Its definitely supposed to be _below_ the signal on the 
> > highest band.
> 
> Yes. That's what I said.
> 
> > I tried it on the next highest band but there 
> > is not enough range in the adjustments to do it and 
> > calibration is reasonable so I think its supposed to be 
> > below there two.
> 
> Yes. Here is what I just read yesterday:
> 
> "The local oscillator operates 455 Kc lower than the incoming signal on the 18-31 mc and 10-
> 18 mc band, but 455 kc higher than the incoming signal on all the rest of the bands."
> 
> > On the others its supposed to be higher. 
> > If its supposed to be higher on the 10-18 mhz band then 
> > something is wrong.
> 
> No, It is supposed to be lower there. That is correct, and is proven by the fact that 20 meter 
> calibration is quite good.
> 
> > Curiously, the band spread calibration 
> > on 20 meters is quite good, its the two lower bands where 
> > its off. 
> 
> Yes. That means that the upper bands, 10-18 and 18-31 mHz bands, are correct, but your 
> lower bands are incorrect.
> 
> > From the symptoms it looks like the overall 
> > capacitance is too _low_ there causing the band spread cap 
> > to have to move more than it should.
> 
> That, alone, would indicate to me that the LO is BELOW the incoming signal frequency, and 
> it SHOULD be ABOVE the incoming frequency. Higher frequencies require LESS 
> capacitance-change to cover more frequency range. The very fact that you say it appears to 
> not have enough capacitance indicates to me that the LO is on the wrong side of the 
> incoming signal.
> 
> > Too low would suggest 
> > that if the LO were above the signal it should be moved 
> > below it but its already below it.
> 
> No. That is backwards. If there isn't enough capacitance, that would indicate the LO must be 
> ABOVE the signal frequency, but isn't, since higher frequencies require less capacitance. If 
> the LO is below the signal frequency, then that is backwards.
> 
> > The total capacitance is 
> > the combination of the main tuning cap and the trimmer cap. 
> 
> Yes.
> 
> > Obviously it must be greater to move the LO lower.
> 
> Yes, but that is only part of the point: the total capacitance required for resonance at HIGHER 
> frequencies is LESS than that required for resonance at LOWER frequencies. Therefore, if 
> you don't have enough capacitance to resonate the circuit when the LO is BELOW the signal 
> frequency, then the LO is on the wrong (LOW) side of the signal frequency, and must be 
> moved above.
> 
> > If I 
> > changed the LO to being above the signal it seems to me it 
> > would make this condition worse not better.
> 
> No. The opposite would be the case. Higher frequencies require LESS capacitance for the 
> same "Q" and for resonance.
> 
> Possibly I'm not making myself clear. I insist that the LO is on the wrong side of the signal 
> frequency for 80 and 40. It MUST be ABOVE the signal frequency, and yours is OBVIOUSLY 
> below it.
> 
> > In any case, 
> > when I try that the core on the inductor want's to be all 
> > the way out and still won't quite make it. When below the 
> > signal the inductor is in a reasonable place.
> 
> That simply indicates to me that the whole thing is out of whack. What I would do is 1) center 
> the core of the inductor, 2) adjust the CAPACITANCES (reduce them) at the high end of the 
> band(s) to make certain the LO is ABOVE the incoming signal frequency and aligned, and 3) 
> THEN tweak the core of the inductor at the low end of the band to get things in total 
> alignment there, and lastly 4) go back and forth to finalize the alignment at the ends.
> 
> A thought just occurred to me: does the manual suggest that you set the bandspread 
> capacitor at a different setting for the lower bands then for the higher (10 MHz and above) 
> bands when doing the alignment?
> 
> > I've inspected all the capacitor sections carefully and 
> > none appears to be decentered and there are no bent plates.
> 
> That fact that the receiver works fine above 10 MHz would indicate that there is absolutely 
> nothing wrong with the tuning capacitor.
> 
> > This may be something obvious that I am missing.
> 
> See above. ;-)
> 
> Ken W7EKB