[Hammarlund] HQ-170 vs. HQ-170A - Differences?

[peter markavage]

And the 170A and 170A-VHF had a number of component and circuit changes
in the AGC section to improve the SSB reception over the 170. There were
at least two field bulletins to improve the AGC in the 170. From a cold
start, my 170A-VHF requires at least a 45 minute warm up time to bring
the calibration back into spec. If AM only and better fidelity is your
bag, stagger tuning the IF sections, will help. Unfortunately,
selectivity is suffer during crowded band conditions. I also replaced the
front end RF amplifier with a 6DE6. No change in component values but had
to re-tweak the front end. Provides higher gain and good for the higher
bands.

Pete, wa2cwa

On Tue, 1 Mar 2005 16:22:01 -0500 "Al Parker" <anchor at ec.rr.com> writes:
> Hi Roy,
>     Quick shot at it -- The A has fil. voltage on the 1st mixer &
> oscillator tubes when power is off, and also has diode rectifiers in 
> the
> p.s.  (no difference in transformers).   The A may have a flip top 
> case,
> not sure if that applied to the 170A or just the 180A.  They're both 
> nice
> rcvrs, the A a little better just for those reasons, I don't 
> remember any
> other ckt differences, and I've had some of each.  I put a small 
> fil. xfmr
> that was only stout enuf for one tube, the osc.,  into 2 "plains", 
> and it
> helped noticeably, plus SS'ing the p.s. to reduce a little heat.  
> Watch
> out for stuck slugs in the RF & IF cans.
> Al, W8UT
> New Bern, NC
> BoatAnchors appreciated here
> http://www.thecompendium.net/radio/
> http://www.hammarlund.info
> 
> ----- Original Message ----- 
> From: "Roy Morgan" <roy.morgan at nist.gov>
> To: <hammarlund at mailman.qth.net>
> Sent: Tuesday, March 01, 2005 3:54 PM
> Subject: [Hammarlund] HQ-170 vs. HQ-170A - Differences?
> 
> 
> > Hammarlun-ites,
> >
> > I just got an HQ-170A, (working but not well.)
> >
> > What's the difference compared to the HQ-170?
> >
> > Experience, advice, lore and stories on the 170A welcome.
> >
> > Roy
> > - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> > 7130 Panorama Drive, Derwood MD 20855
> > Home: 301-330-8828 Cell 301-928-7794
> > Work: Voice: 301-975-3254,  Fax: 301-948-6213
> > roy.morgan at nist.gov --