[Hammarlund] Hammarlund Audio

[Kim Herron]

Hi again Gang,

>I also had a HQ-170 with muddy audio. After a careful alignment (especially
>the 60kc IF) the audio response was greatly improved.
> >my HQ180,
> >while a better radio, has pretty muddy sounding audio. There's just no
> >high-end response at all. I'm wondering what differences there are in audio
> >reponse between the various Hammarlunds you have. Do they all sound about
> >the same, or do some of them sound better than others? I've never heard of
> >any mod to improve the audio of the HQ180.

     Something else that I failed to mention is the First IF crystal filter 
in these two radios.
That filter works at 3035 kc and IF you notice an audio (or sensitivity) 
problem on the bands where
the receiver goes to triple conversion (upper two bands on the 180), you're 
very likely dealing with a crystal filter
or 2580 oscillator crystal that is off-frequency.
If it's not centered with the 455 kc oscillator, you'll seriously degrade 
one sideband of the audio, and you'll
usually find it's apparent by changing sideband selection.  The receiver 
will work fine on 80 meters
on either sideband, but it stinks on 20 and up.  You may have to change the 
crystal to get it to work,
or just realign the first IF.  Again, this calls for a VERY accurate signal 
generator and being VERY
fussy when you align.  Remember this:  These receivers have IF shift, 
rejection tuning, and RC filtering
all in the IF stages.  IF all the oscillators aren't aligned and in sync 
with each other, you attenuate one
of the sidebands in the conversion process and when you do that, you 
degrade sensitivity and audio quality.
Remember too, that you should have your slot control turned all the way 
counterclockwise, and the vernier tuning
control (If you have one) at center or zero.  That puts the IF notch (or 
rejection tuning) control at the point where it's
at the lower edge of the third IF passband, and the vernier tuning (IF 
shift) control where the third IF is lined up
with the second IF passband center.  I've seen receivers that people were 
using with these controls in the wrong places
and they sound lousy because of it, but they are doing just what they're 
set up to do.  Put the controls where
they belong and they work just fine.




Thanks!!

Kim Herron
1-616-677-3706