[ARC5] Potentiometer value needed

[Glen Zook via ARC5]

At least on the BC-348, it is possible to "split" the AF and RF controls without having to drill any additional holes.  There are 2-headphone jacks on the lower left-hand side of the receiver.  Remove the bottom jack and install the additional control in this hole.  I did this in my BC-348 several decades ago!  I also added an audio transformer to use a speaker with the receiver and added a jack on the removable plate in the upper right-hand corner.  There is a very good audio level using the speaker without any modifications in the audio circuits.
 
Glen, K9STH 

Website:  http://k9sth.net


On Sunday, August 10, 2014 7:29 AM, Geoff <geoffrey at jeremy.mv.com> wrote:
 


As a Q5'er there will be excessive gain so Id suggest starting with a 
125-150V B+ and then use a trimpot to finalize the RF stage gain as it will 
already be seeing more signal from the main receiver than it was designed 
for.

If you want to get creative extend the main receiver AGC to the BC-453 and 
remove the rather useless circuitry as built. Inject the BFO into the last 
IF or build a SS product detector around 1N5711's for AGC on CW.

Carl


----- Original Message ----- 
From: "D C _Mac_ Macdonald" <k2gkk at hotmail.com>
To: "VK2GCE Brian Clarke" <brianclarke01 at optusnet.com.au>; "W7EKB Ken 
Gordon" <kgordon2006 at frontier.com>; "Jim Falls" <radio-tuber at att.net>
Cc: "ARC-5 Mail List" <arc5 at mailman.qth.net>
Sent: Saturday, August 09, 2014 9:37 PM
Subject: Re: [ARC5] Potentiometer value needed


>I wonder if a concentric (dual) wirewound pot could be found to serve as 
>both RF/IF gain AND audio gain controls.  OR a pair of miniature pots for 
>that purpose?
>
> * * * * * * * * * * *
> * 73 - Mac, K2GKK/5 *
> * (Since 30 Nov 53) *
> * k2gkk hotmail com *
> * Oklahoma City, OK *
> * USAF & FAA (Ret.) *
> * * * * * * * * * * *
>
>
>> From: brianclarke01 at optusnet.com.au
>> To: kgordon2006 at frontier.com; radio-tuber at att.net
>> Date: Sun, 10 Aug 2014 11:28:30 +1000
>> CC: arc5 at mailman.qth.net
>> Subject: Re: [ARC5] Potentiometer value needed
>>
>> Hello Jim,
>>
>> Because there is DC on the pot, if you use a carbon-tracked pot, it will
>> soon become noisy. It is far better to use a wirewound pot, as in the
>> original design.
>>
>> If you plan to fit Ken's suggested AF gain control in the front of the
>> receiver, shield both audio leads.
>>
>> 73 de Brian, VK2GCE.
>>
>> On Sunday, August 10, 2014 7:47 AM, Ken suggested:
>>
>>
>> > On 9 Aug 2014 at 14:21, Jim Falls wrote:
>> >
>> >> I have a lightly hacked (12 filament mod) silver BC-453-B with an 
>> >> on/off
>> >> switch,
>> >> volume control and phone jacks in the front cubby hole. Current pot is
>> >> far to
>> >> touchy and probably linear taper. What's a good value audio taper to 
>> >> use
>> >> for
>> >> hi-Z phones/speakers? I'd like to try it with my TCS and others.
>> >
>> > Hi, Jim:
>> >
>> > That "gain control" is a combination RF/IF gain pot acting on the
>> > cathodes. I
>> > have found that a 50K log (audio) taper pot works well there.
>> >
>> > Since you are, apparently, going to use that BC-453 as a "Q-5er" for 
>> > your
>> > TCS receiver, I suggest that you add an AF gain control to it.
>> >
>> > Use a 2 megohm (or a 1 meg) log-taper pot to replace R-20, the 12A6 
>> > grid
>> > resistor, then connect the wire that attaches to the 12A6 grid 
>> > connection
>> > which comes from the flat .006 mfd capacitor to the pot wiper.
>> >
>> > Ken W7EKB
>
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