[ARC5] [Milsurplus] BC-221AK Question

[Frank Barnes]

I keep a gifted LM-8 (a Navy version of the BC-221)
<https://maritime.org/tech/radiocat/lm.php> on my workbench as a frequency
generator.  Extremely accurate.  Nearly 80 years old, I think but I can't
find the production date.  I also have a nice BC-221 and a third unit (Army
version) awaiting restoration.  I really like these old units.
W4NPN

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On Wed, Aug 27, 2025 at 10:50 PM kgordon2006 <kgordon2006 at frontier.com>
wrote:

> I really like my -AKs too. I find them to be unusually accurate and stable
> for bring 70 years old.
>
> Ken W7EKB
>
>
>
> Sent via the Samsung Galaxy S21 5G, an AT&T 5G smartphone
>
>
> -------- Original message --------
> From: JAMES FALLS <radio-tuber at att.net>
> Date: 8/27/25 18:40 (GMT-08:00)
> To: Mark K3MSB <mark.k3msb at gmail.com>
> Cc: Ken Gordon <kgordon2006 at frontier.com>, ARC5 <ARC5 at mailman.qth.net>,
> List Milsurplus <milsurplus at mailman.qth.net>
> Subject: Re: [ARC5] [Milsurplus] BC-221AK Question
>
> Yes! The -AK is my favorite of the -221 series. Love it!
>
> Funny anecdote: Mine came to me via a friend who’d stopped at a wide spot
> on a rural road here in NorCal to relieve himself. He spied it 20’ down the
> hill (out of range 😛😁). It was the innards, no case. A bit dusty from its
> trip down the hillside.
>
> I checked it out and it worked perfectly! Just a scant few PPM off of WWV
> when enclosed and warmed up. I found a non-battery cabinet and ran it with
> a separate PSU. I aligned and debugged all my milsurplus radios with it.
> 😎👍
>
> Jim Falls K6FWT
>
> On Aug 27, 2025, at 17:34, Mark K3MSB <mark.k3msb at gmail.com> wrote:
>
> 
> Hi Ken
>
> >> The cap is part 9-2, not 0-2 and it is supposed to be 0.001 uF.
>
> Yes, my typos.   Too lazy to roll over to the bench and get my
> glasses........     :-)
>
> <image.png>
>
>
> .... and thus the motivation for my question....
>
> <image.png>
>
>
> <image.png>
>
>
> The internal HB Power Supply was a "Widow-Maker" Special......with leaky
> caps!!!
>
> I will rebuild the PS tomorrow and power it up (after dressing the
> connections associated with the replacement components.....and using the
> correct parallel capacitor.
>
> 73 Mark K3MSB
>
>
>
>
> On Wed, Aug 27, 2025 at 7:46 PM Kenneth G. Gordon <
> kgordon2006 at frontier.com> wrote:
>
>> On 27 Aug 2025 at 18:56, Mark K3MSB wrote:
>>
>> > I have a BC-221 whose ID plate says  BC-221E.   It is not an E
>> > variant.
>> > From the tubes, front panel controls, and TM11-300,  I think it's the
>> > AK variant.
>>
>> I have two -AKs here: unfortunately. in storage, not in the shack. :-(
>>
>> > Looking at the front panel,  what is supposed to be behind the two
>> > antenna connectors?
>>
>> Well, only ONE is an antenna connector: the "other" one is a ground
>> connector...or should be.
>>
>> > I tried discerning it from TM11-300.   I think it's supposed to be a
>> > 150 H Choke (Part 24) in parallel
>> > with a 0.01 uF cap (Part 0-2).
>>
>> The cap is part 9-2, not 0-2 and it is supposed to be 0.001 uF.
>>
>> >    Can anyone confirm?
>>
>> Well, a 150 H choke would be physically fairly large for a "small" choke.
>> I would have to go to my storage building and open one of my -AKs up to
>> check, and cannot do that just now.
>>
>> I hope Wayne can help. If all else fails, I'll make a run to my storage
>> and take look as soon as I can.
>>
>> BTW, the -AK version is one of only two other versons which include AF
>> modulation capability. None of the others have that. This makes the -AK a
>> fully functioning signal generstor.
>>
>> Ken W7EKB
>>
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-- 
Frank Barnes
www.W4NPN.org <http://www.W4NPN.net>
Chapel Hill, NC
Grid Square FM05
Cell 919.260.7955
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