[Hammarlund] Tim-HQ170 audio

[Peter A Markavage]

Les:

Several guys on the AM reflector have done the mod and noted some
improvement in the audio. However, due to the nature of the design, with
dual or triple conversion being used, depending on the band selected, the
audio will never be as good as a single conversion receiver with its
inherently broader bandwidth. As Greg mentioned in his post, the chances
of some phase distortion being introduced into signal stream, due to the
various conversions, is also a possibility. 

The 170 and 180 were designed with sideband in mind as the primary mode.
If you follow the alignment procedures to the letter, you'll wind up with
a receiver with great sensitivity and selectivity but "average" AM audio
out. On SSB, the receiver should sound great for sideband (but even this
subject to the listener's ears). Some consideration should also be given
to the audio output circuitry along with their "auto-response" circuits.
Some changes probably could be made here to further improve internal
audio output. 

As the article further mentions, some people have "redone" the alignment
of the IF stages to have a much flatter response. Basely a bit of stagger
tuning of the IF stages. This degrades the selectivity but allows the
receiver to sound "better" in the AM mode. Further, if you pull the
output signal off the detector and run it to 10 to 20 watt Bogen-type
amplifier (pp 6V6's/ 6K6's, etc.), you could really vibrate your woofer
with CHU time tones.  The stock 170/180's are great communications
quality receivers. For Hi-Hi FB AM quality, they could never replace some
of Hammarlund's earlier receivers.

Pete

On Mon, 31 May 2004 17:55:34 -0700 "wb6orz" <wb6orz at pacbell.net> writes:
>     Nice post. I went to the link and enjoyed and printed the mod.
>     Pete, i tend to stick with the radios as designed, but this is a 
> pretty
> tempting mod. Do you know if in fact it results in better audio? And 
> what
> about better sideband audio? I am also not allergic to mods.
>     I am tempted, but would like some opinions.
>     After yours, maybe I'll query the reflector. I have the 170 and 
> 180, and
> have always found the audio lacking. My 110 and 145 do sound better, 
> but
> before I hack any nice old BA's I wanna' be sure...
>     Thanks, Pete.
>     (((((73)))))
>     Les
>     ---===WB6ORZ===---
> ----- Original Message ----- 
> From: "Peter A Markavage" <pmarkavage at juno.com>
> To: <hammarlund at mailman.qth.net>
> Sent: Sunday, May 30, 2004 10:05 PM
> Subject: Re: [Hammarlund] Tim-HQ170 audio
> 
> 
> > Here's some info off the AM Window Mods page. It addresses the
> > shortcomings in the Hammarlund 170/180 audio.
> > http://www.amwindow.org/tech/htm/hqaudiomods.htm
> >
> > Pete, WA2CWA
> >
> > On Sun, 30 May 2004 23:54:17 -0400 "Mike Taylor" 
> <reel2reel at hotmail.com>
> > writes:
> > > Tim...My HQ-180 suffers from the same problem. Muffled audio 
> with no
> > > high
> > > end on A.M. My HQ-110C on the other hand, has excellent audio 
> which
> > > borders
> > > on high fidelity. (I run both radios through my Hi-Fi system.) 
> I've
> > > asked
> > > about this on this list as have others over the last couple of 
> years
> > > and no
> > > one seems to have a fix for this. The HQ-180 and HQ-170 are 
> both
> > > very
> > > selective and therefore have narrow audio bandwidths. Maybe 
> someday
> > > some
> > > genious will come along with a way to clean up the poor audio 
> of
> > > these
> > > otherwise very fine receivers. 73's...Mike