[Hammarlund] HQ-129-X Serial Numbers

[Kenneth G. Gordon]

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