[Milsurplus] BC-221 types

[Michael D. Harmon]

I have owned a number of BC-221 freq meters over the years.  If you have 
a calibration book WHOSE SERIAL NUMBER MATCHES THE INSTRUMENT, these 
meters are darn near on the money!  I have seen units before at hamfests 
which had a cal book that been taken from another instrument.  Watch out 
for that!  The great thing is that the frequency-determining components 
of these meters are 100% mechanical -- a wax-coated coil and a variable 
cap milled out of a piece of brass.  Unless there has been physical 
damage to the meter, it should be within a few Hz of WWV.  I have put a 
number of the crystals in these units  up against WWV and could barely 
detect a low-frequency beat note.  The only unit I currently have is an 
AK model in a lightweight TS-164 aircraft housing.  There's enough room 
in the back of the TS-164 to build a solid state power supply which puts 
out 135V at about 20 mA and 6.3V at about an amp.  Watch out for paper 
caps in these old units - they are notoriously failure-prone - including 
the 'molded paper caps' that masquerade as micas.  The oil-filled 
bathtub caps are probably OK unless they're leaking.  Oh, BTW, you 
really need to use a (relatively) high-Z headset like an HS-30 with 
these meters.  You won't hear anything if you plug in a modern 8 ohm 
headset.  Hallicrafters made a tube-type AC supply called the RA-133 
that fits in the back of one of the big metal-cased BC-221s

Here's the definitive reference for the entire series of BC-221 freq meters:

    http://w5jgv.com/downloads/BC-221_SCR-211.pdf

The half-tone photos aren't too readable, but the book is invaluable for 
anyone interested in BC-221s.  I've also seen the book (TM-11-300) turn 
up from time to time on E-Pay.

I love these old meters.  Over the years, I've rebuilt and refurbished 
more than I can remember, including replacing some really badly-hacked 
homebrew AC power supplies.  I'm sort of a sucker when I see one sitting 
neglected under a table at a hamfest. They may be 70 years old, but 
they're still nice to have.  You can't put a receiver on frequency with 
a counter!

If you'd like to have a copy of the pdf for the RA-133 power supply and 
the TS-164 aircraft housing, please email me direct.

Hope this all helps ...
Mike, WB0LDJ
mharmon at att dot net