[Heathkit] Audio gain pot and FAST/SLOW AGC

[Tom NØJMY - AAR7FV]

Hi, Ken et al.

I like to use these switch/pots on HW-16's in place of the "REL PWR" and 
the "RF GAIN".  My favorite is to turn a little narrow AF filter on and 
off with one of the switches.  The other one can be used to switch to 
Ade Weiss's simple qrp conversion, although you really are limited only 
by your imagination when it comes to what you can use it for.  
QSK/non-QSK is another one.

Vy 73,
Tom

Kenneth G. Gordon wrote:
> On 7 Mar 2007 at 23:54, Chris Kepuardss wrote:
>
>   
>> Hi Ken,
>> If anyone has a source for these and replies off list, would you be
>> kind enough to share that info with me?  
>>     
>
> You bet! See below.
>
>   
>> Your idea to use an existingen 
>> "pot hole" (our Transportation District folk would enjoy that!)
>>     
>
> Hee hee! So do I! :-)
>
>   
>> to be
>> able to add a switching function while retaining the original control
>> is very clever. 73, Chris W7JPG
>>     
>
> Gee! Thanks for the compliment Chris, but it wasn't originally my idea. I 
> cannot now remember where I first heard it, but the time frame was 
> back in the late 1960s. It may even have been in a Hints and Kinks.
>
> Here is what Tom N0JMY sent to me:
>
> http://www.vibroworld.com/parts/tech14.html
>
> as a possible source, which I will check out this morning.
>
> The way you implement the FAST/SLOW AGC is fairly easy. 
>
> First, install the 1 meg pot with a push-pull SPST switch on it in place of 
> the original AF gain control.
>
> Then, find the AGC timing capacitor. I can't remember the proper 
> number right now, but it is easy to find, and is a fairly large value. 
> Looking in the Circuit Description section of your manual for the AGC 
> system will show it pretty quickly.
>
> Then, lift the ground end of that capacitor, and connect it to one side of 
> the switch. Connect the other side of the switch to the nearest handy 
> ground point.
>
> Then, pulling the switch gives you FAST AGC, and pushing it in gives 
> you SLOW or NORMAL AGC, or vice-versa depending on how the 
> switch is set up.
>
> In any case, since you are using the audio gain control for this function, 
> it is very innocuous.
>
> The FAST position makes a big difference on CW and certain digital 
> modes like Pactor or AMTOR.
>
> My next project is to make the necessary modifications to the MODE 
> switching so that both the offset and the CW sidetone are about 750 Hz 
> instead of that terribly annoying 1Khz canary tweet.
>
> Ken Gordon W7EKB
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