[ARC5] BC-221 question

[Robert Downs]

There were 26 production models of the BC-221 from -A through -AN.  I am not sure what happened to the -AM.  There were several letters skipped for one reason or another.  The -AN was covered by Change 1.

Robert Downs


-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Richard Knoppow
Sent: Saturday, May 23, 2020 02:36
To: Ken Gordon; arc5 at mailman.qth.net
Cc: Milsurplus at mailman.qth.net
Subject: Re: [ARC5] BC-221 question

    I had to look, turns out mine is an AN not an AK. The trimmer 
on mine is inside facing the back. Actually, there is a tube in 
the way. Its a PITA to adjust because when the chassis is removed 
from the case the power supply is disconnected so its necessary 
to do a little patching. Then, of course, the chassis is in the 
open air where in normal use its in a wooden case so the effect 
of heat is there. I got the crystal about right by a series of 
small adjustments and then letting it run in the case for a day. 
Once as close as I could get it I just left it alone. The 
adjustment is well within the specs. I was reminded that the 
modulator seems to work only on the crystal. I remember studying 
the schematic to see how it worked but don't remember exactly now 
other than I decided to leave it alone. Mine was made by Allen D. 
Cardwell. I think the design may have originated with them but 
don't remember what I found. There were perhaps fifteen different 
versions of the BC-221, there is a comprehensive handbook on the 
web. Mine is very ruggedly  built and weighs a ton.

On 5/22/2020 6:29 PM, Kenneth G. Gordon wrote:
> > The cabinet is supposed to be sealed but
> > getting the crystal on frequency is a PITA unless you drill a
> > hole to access the trimmer from outside.
>
> No! Under that small plate in the center of the front panel 
> immediately below the tuning knob there is a trimmer capacitor 
> for that crystal.
>
> You have to remove the plate to reach it.
>
> BOTH of my AKs have that.
>
> Ken W7EKB

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL

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