[Hammarlund] gregg 129x

[Al Parker]

Hi Greg, et al,
    I'll agree with Les (& Boomer mostly), but will add a little about the
double/triple conversion vs the single in the HQ-129.  Single conversion is
prone to images.  The lower the IF freq, the more susceptible to images, but
the less easy to make selective.  So, "they" picked a freq high enuf that
was hopefully below any freq recd (like 455 or 500 kc), and low enuf to be
reasonable selective (without mech. filters).  So, image freqs. are
separated from the recd freq by twice the amount of the IF, and the
direction dependant upon whether the osc. is above or below the recd freq.
On lower recd freq., the RF stage is selective enuf to eliminate images, but
not so at higher freqs.     (enuf of that stuff)
    So, take 10 meters, for example, with single conversion, 455kc IF
(HQ-129 or many others) if you're tuned to 28.0 to 28.5, you're likely to
also hear signals between 27.09 and 27.59. 26.965-27.405 happens to be the
area allocated for legal CB, and there's plenty of non-legal activity (hi
power) in there & between there & 28.0+.  So, at only a slightly reduced
signal level, you'll be hearing many signals that "aren't really there"  -
images.  It'll happen, to a lesser degree, on 15 & 20 meters, with foreign
BC or commercial signals.
    With double, or triple conversion, images are essentially eliminated.
The first IF is high enuf to let the RF stage's selectivity eliminate the
image, and the 2nd IF is low enuf to allow easily obtained high selectivity,
without filters.
    Most of us who have operated on 10m during good propagation conditions,
with a single conversion rcvr, know & hate the problem.
    As Les said, take a look at our Hammarlund Historian website:
<http://www.hammarlund.info>
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info


---- Original Message -----
From: "Mike Taylor" <reel2reel@hotmail.com>
> Gregg, I did forget something. the 180's AVC system works in both AM and
SSB
> modes. And you can select "off", "fast", "medium" or "slow". There's a
> number of neat websites devoted to Hammarlund with photo galleries and
other
> information. Glenn Zook is a regular here and I think his websit may have
> some Hammarlund links. I don't remember his web address but he puts it up
> here frequently. Mike
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