[Hammarlund] Distortion in HQ-180 audio output

[Robert Sauvan]

Thanks Gordon,
I have that article somewhere and do remember reading it. I will have to 
look on my other computer though because it isnt on this one. I have 
ordered that issue just so I have it anyway. Thanks for the tips.

Bob-W0YBS




On 12/18/2014 11:09 AM, Kenneth G. Gordon wrote:
> Robert:
>
> OK. I found the article in ER Mag I remembered: it is in issue number 304,
> the September 2014 issue, beginning on page 12. Single issues are very
> inexpensive and I would advise you to get that issue before you start on your
> audio distortion problem.
>
> Distortion on strong CW or SSB signals was a very common problem in
> many receivers of the period of the HQ-180.
>
> The problem in the HQ-180 is caused by an incorrect or incomplete
> application of AGC.
>
> In the case of the HQ-180, there are two AGC loops: 1) a delayed AGC for
> the 1st RF amp only, and 2) a "main" loop for the other controlled stages.
>
> In the HQ-180, the 2nd loop controls the 455 KHz IF stage, and only ONE of
> the two 60 KHz IF stages, V-6.
>
> The author of the article, Jeff Covelli WA8SAJ, connected the 2nd 60 KHz IF
> stage, V-7, to the AGC buss. This reduced the distorted audio very
> dramatically.
>
> In the Heathkit Mohawk, there is NO AGC connected to either of the two 50
> KHz IF stages. He added those stages to the AGC buss, and the effect on
> that receiver was the same as for the HQ-180: dramatically reduced
> distortion of the audio on CW and SSB.
>
> I strongly suggest that you contact Ray at www.ermag.com and buy that
> issue of ER magazine asap.
>
> Those improvements that Byron mentioned should also be investigated,
> especially, IMHO, that one which improves the AGC attack-time.
>
> Kenneth G. Gordon W7EKB
>
> "Courage is being scared to death but saddling up anyway."--- John   Wayne
>
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