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Author Topic: Looking for information on Hammarlund mods  (Read 1768 times)
K7WXK
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Posts: 68




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« on: August 28, 2012, 07:31:36 AM »

I am considering trying to mod my HQ-160 (or one of my older HQ's) so that the AVC and S-meter work on CW/SSB.  Is there a source out there where I might find more information on this topic?  If so, does anyone know how involved this mod will be?

Thanks in advance,
Marc-K7WXK
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W9GB
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Posts: 2613




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« Reply #1 on: August 28, 2012, 09:18:20 AM »

Hammerlund HQ-160 Owner's Manual
http://www.hammarlund.org/files/HQ-160.pdf

Correct, no AVC in SSB/CW, per stated specifications (this is export model)
http://personales.ya.com/old-timers/hq-160/hq-160tech.htm

This page discusses the AGC for SSB/CW
http://personales.ya.com/old-timers/hq-160/hq-160.htm#agc-stages

Curtis Eicherman, at Antique Radio Restorers Forum, offers this modification (Jan. 2012) for
AGC operation with SSB/CW.  Capacitor selection will determine AGC time constant.
Resist temptation to punch holes in metal chassis (front/rear panel).
http://www.antiqueradios.com/forums/viewtopic.php?f=5&t=195258

The 6BJ7 is the Triple Diode for AM detection, ANL, and AVC.
This radio is a dual conversion receiver, here is spec sheet.
http://www.hammarlund.org/HQ-160.html

Hammerlund HQ-160
http://antiqueradio.org/hamm02.htm

Antique Radio Restorers Forum - The Collector's Resource
http://www.antiqueradios.com/forums/viewtopic.php?t=90749
« Last Edit: August 28, 2012, 09:40:15 AM by W9GB » Logged
K7WXK
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Posts: 68




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« Reply #2 on: August 28, 2012, 09:47:45 AM »

Looks like a wealth of knowledge.  I will review it and hopefully find my answers.

Thanks for your input.

Marc
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W8JI
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Posts: 9304


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« Reply #3 on: September 02, 2012, 04:58:10 AM »

I've installed CW and SSB AGC in many radios that originally were manual gain only.

This always involves making the AGC detector immune to the BFO signal. This means you either use audio derived AGC, or you use AGC taken from ahead of the BFO injection.

Unless someone has laid groundwork for you or you understand the system very well, this can be difficult. The basic problem is always that the BFO signal saturates the AGC detector, unless the sample point is immune from BFO signal.

73 Tom 
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