[Milsurplus] BC-221

[Ray Fantini]

End results of the BC-221 project, Thanks for everyone's input on the
BC-221 project. I am amazed by that fact that a almost sixty year old
frequency meter that I paid a whole $10 for last year at Dayton still
works, is stable within a couple cycles after warm up and is right on
frequency when used with its internal crystal. After some
experimentation with different B+ voltages I settled with using 105
Volts DC, my home built power supply produced around 135 to 140 Vdc
unregulated, and with no regulation the unit was stable but prone to
change frequency with AC line variations, the end result was that this
unit benefits from a regulated power supply. The new power supply was
built to fit inside the bottom of the meter, having run the power supply
for several hours outside the box have noticed no heat from it so will
install it in the base of the meter, maybe the old vacuum tube version
produced heat but this one uses a silicon diode. 105 volts may be a
little low but the only choice I had was 0C3 and 0D3 for regulator
tubes, and not having 150 volts for a 0D3 settles that, almost used a
ziner diode but wanted to use a tube. The use of a silicon diode for the
power supply was a compromise but its hard to find transformers that
will provide a center tap and isolated five volt winding and besides no
one will see the power supply when installed in the meter so I can still
say I have my tube and solid state stuff separated. I put a link on my
web page (www.ka3ekh.net) called "project of the week" where you can see
pictures of the working BC-221 and the power supply.
Thanks for all the help, 
Ray Fantini