[Hammarlund] HQ140X

[Richard Knoppow]

----- Original Message ----- 
From: "Bill Kulze" <wak9 at cornell.edu>
To: "GRANT YOUNGMAN" <nq5t at tx.rr.com>; 
<Hammarlund at mailman.qth.net>
Sent: Monday, March 24, 2014 12:54 PM
Subject: Re: [Hammarlund] HQ140X


> -----Original Message-----
> From:] On Behalf Of GRANT YOUNGMAN
> Subject: Re: [Hammarlund] HQ140X
>
> I just did the alignment on an HQ-140X this past week. 
> Used a sweep generator and a scope with a log detector. 
> It was really instructive.
>
> You can simply peak all of the transformers on the crystal 
> frequency.  You will actually get a higher maximum IF 
> output doing that, but you also will get a narrower 
> "peaky"  passband with a funky shape rather than something 
> with a nice symmetrical shape and a flat (well, really 
> somewhat rounded) top.
>
> Bill's idea is correct - you really do want to try to get 
> a symmetrical passband if possible.  The radio will sound 
> better with greater fidelity.  It's tedious to do by hand, 
> but will give you a better result if you have the patience 
> for it.  Z3 is the most critical to the overall shape. 
> Also the top core on Z4.  The bottom core on Z4 did not 
> change the overall passband shape much, just the gain.
>
> Do it the way the manual recommends.  One stage at a time 
> starting with the last IF amp and moving towards the front 
> of the chain.
>
> Grant NQ5T
> ___________________________________
>
> When I first got the 129x I did the 'peak them all' 
> method, not even at xtal resonance, wasn't real impressed 
> with the sound. When I used the scope I found that peaking 
> at center doesn't give you a true peak at center. It 
> merely gets you the max level the center can be, the peak 
> is off center someplace, you won't notice without moving 
> the generator back and forth. I think that's what made it 
> sound bad, having the peak in some other place in the pass 
> band. I discovered this almost by accident after I 
> recapped it and decided to do the alignment at the 
> detector using a scope instead of a meter. It sure made a 
> difference in audio! At first I was concerned about losing 
> some gain by flattening the IF out a bit, but the darn 
> thing has plenty of gain to spare.
>
> Adjusting 'by the ear' might get you close, but the visual 
> reference makes it much easier.
>
> I would think the proper method with a sweep generator 
> synced with a scope is best, but I would recommend doing 
> this at the very least if you don't have the equipment to 
> do it proper.
>
> Bill
> W2NVD

     One problem with manual adjustment is that you don't 
know what the separation of the peaks of the overcoupled 
transformer should be.  It appears that there is one 
overcoupled transformer in any of these receivers. It should 
be possible to align it individually but I have not tried 
this.  I have done an alignment of an RCA AR-88 without a 
sweeper. This receiver has two double IF stages which have 
two degrees of coupling, both over-coupled, but the peak 
spread at the widest setting is in the CR-88 handbook. So, 
one can alternate the four adjustments for each stage until 
the bandwidth is correct for the "wide" setting.  Its not 
too difficult to do, I used a scope probe on both generator 
and meter. However, a sweeper would make life much easier. I 
think something like this can be done on the HQ receivers. 
The double peaks are probably separated by around 5 khz. In 
any case it should be possible to tell when you have two 
separated peaks of the same amplitude. The combination of 
critically coupled and overcoupled IFs results in both a 
fairly flat passband and also steeper skirts than you would 
get from just critical coupling. The audio quality is quite 
good. The Hammarlund crystal filter is a snap to adjust and 
does not require a sweeper.  The crystal frequency should be 
used as the center frequency of the IF so that the dip 
between peaks of the overcoupled transformer is at this 
frequency.  The whole HQ series are remarkably good 
receivers considering they were meant to be the economy 
model. About the only real shortcoming is the lack of image 
rejection but its no worse than other single RF receivers 
with 455kc IFs.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com