[ARC5] BC-221 and LM on eBay

Thu Mar 31 18:27:39 EDT 2022

    This thread on the BC-221 caused me to take mine off the 
shelf and fire it up. Mine is a BC-221 AN. I've had it for 
decades and don't any more remember buying it. It has an AC power 
supply (would have to look at the type number. In the past I've 
cleaned it but don't remember having had to do any repairs to it. 
It seems to work fine but the modulator didn't work. I looked at 
the schematic and decided it might have a bad capacitor. I took 
out the chassis and poked at the wiring. Decided the capacitor  I 
was suspicious of was too hard to access, at least until I was 
sure I had a replacement. However, I did poke and move it a 
little. Put the think back in its case and found the modulator 
now works fine.
    My main problem in the past was getting the plug for the 
power supply to line up with the chassis. Did it but its a 
tedious job. Its still lined up so I guess I got it right.
     The trimmer for the crystal reference is mounted on a shelf 
or step on the chassis that faces the back of the chassis, 
absolutely no way to access it with the chassis out of the case. 
I got it about right and monitored it against WWV for a day. 
Sometimes exactly zero beat but drifts back and forth a bit. 
Always well within the specs. The variable oscillator is quite 
surprisingly stable and can be read within the speced precision 
of the meter. Mine will stay zero-beat with WWV on 15Mhz for 
hours  after perhaps two hours of running.
    The modulator makes it possible to use the meter for rough 
alignment of receivers.
    The only thing missing is the canvas case. I think I once had 
a part of it but there is nothing left now although I do have the 
carrying strap.
     Mine was made by Cardwell. It would be interesting to know 
who originated the design. It may have been the Allen Cardwell 
company or possibly Hammarlund. The Navy LM meter is very 
similar. There are several variations of the BC-221, all are 
similar but have variations of the circuits. I have a sheet for 
the AN sent to me long ago by Robert Downs (who I think is on 
this list) but thought I had a comprehensive manual or reprint on 
the entire BC-221 line with several schematics. Its in my files 
somewhere.
     For working on boatanchor radios these venerable instruments 
are still quite useful and judging from the quality of 
construction should last forever.

On 3/31/2022 9:44 AM, MICHAEL ST ANGELO wrote:
> I've been doing lots of spring cleaning in the basement. I dug out my BC-221T. I believe I picked it up at the Military Vehicle meet in Glibert PA years ago.
> 
> It does have the calibration book. The plastic cover plate is yellowed and has shrunk but the book is in good shape.
> 
> The book is attached to a metal plate which is apparently screwed to the front panel. I am surprised so many sets are missing the book since it would take some effort to remove it.
> 
> By the way, the spring cleaning mostly consisted of getting rid of data books, technical books and magazines, most of which are available online. Fortunately the InfoAge museum in Wall NJ will take most technical  documentation, except for QST (they have every issue). They are more selective on hardware donations but are looking for RADAR equipment. If you have stuff taking up space you may want to contact them.
> 
> Mike N2MS
> 
>> On 03/28/2022 10:24 AM MICHAEL ST ANGELO <mstangelo at comcast.net> wrote:
>>
>>   
>> I picked up a BC-221 and a neighbor gave me a LM frequency meter. He was a high school physics teacher and one of his students gave it to him.
>>
>> What is the published frequency accuracy of these meters? The only notes I could find online is this observation by VE3BDB. He read in the manual that that the maximum error will occur when measuring a 4 MHz signal at minus 30 degrees C where an error of 1.355 KHz (0.034%) could occur. His observations indicated that the BC-221 is easily capable of 250 Hz accuracy on 80 & 40 M.
>>
>> <https://www.qsl.net/ve3bdb/bc221observations.htm>
>>
>> Mike N2MS
>>
>>
>>> On 03/28/2022 8:38 AM Bob kb8tq <kb8tq at n1k.org> wrote:
>>>
>>>   
>>> Hi
>>>
>>> As an “all in one” gizmo for keeping a pile of HF radio gear tuned up,
>>> I still would put the LM / BC-221 pretty close to the top of the list. Yes,
>>> there would be other things on the list as well. With care, you can do a
>>> lot of things with one of them.
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL