[Heathkit] Re: Heathkit FAST/SLOW AGC

[Dick KF4NS]

>   1. RE: Audio gain pot and FAST/SLOW AGC (Kenneth G. Gordon)
>   2. Re: Audio gain pot and FAST/SLOW AGC (Tom N?JMY - AAR7FV)
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 08 Mar 2007 09:26:52 -0800
> From: "Kenneth G. Gordon" <kgordon2006 at verizon.net>
> Subject: RE: [Heathkit] Audio gain pot and FAST/SLOW AGC
> To: "Chris Kepus" <ckepus at comcast.net>
> Cc: Heathkit at mailman.qth.net
> Message-ID: <45EFD6DC.21209.3C0CCF16 at localhost>
> Content-Type: text/plain; charset=US-ASCII
>
> On 7 Mar 2007 at 23:54, Chris Kepus 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 existing
>> "pot hole" (our Transportation District folk would enjoy that!) 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
> ------------------------------
>
> Message: 2
> Date: Thu, 08 Mar 2007 11:47:07 -0600
> From: Tom N?JMY - AAR7FV <tfarl at mchsi.com>
> Subject: Re: [Heathkit] Audio gain pot and FAST/SLOW AGC
> To: kgordon2006 at verizononline.net
> Cc: Heathkit at mailman.qth.net
> Message-ID: <45F04C1B.1090304 at mchsi.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> 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