Hello MIles
I have been making my own spreadsheet to use with my BC-221. I
seem to have trouble with the Royal Signals page in the past. They
will not send me the password as there is some issue with my ISP
not passing their "test". I could never resolve the problem, so I
gave up the last time I tried. I'll try again and see what
happens.
Making my own Excel spreadsheet is tedious, but I can see the
value in it. In re calibrating my own meter, I have found numerous
errors in my book where someone did not get the cal points exactly
correct back in 1942. These may not have been errors as much as
the limits of frequency measuring gear in 1942. I am using a GPS
locked frequency counter that is coupled to the BC-221. I zeroed
the 1000kc crystal and it is within 1 or 2 cycles. Anyway, I
checked the frequency every ten kHz on the 2-4 MHz range, and
entered it into my spreadsheet. The sheet then generates all of
the 1 kHz checkpoints. To make things easier, I adjusted the
amount of dial travel to match the end points of the original
calibration curve. (It has drifted over the 80 years ) In my case
0158.8 was 2.000 MHz and 4699.5 was the end point at 4.000 MHz.
This was accomplished by adjusting the position of a coil shield
on the bottom of the instrument. I was able to remove most of a 13
dial division error down to about 1.4 divisions. I am not
finished with the spreadsheet, but it is going along OK. I have
tried a few measurements on what I have done so far and results
are fantastic. The VFO in the BC-221 is quite good for 1942. The
manual states 0.034% accuracy under most conditions in the field.
That amounts to a 1.36 kHz error at 4 MHz. In a heated room, I am
seeing 0.01% errors typically or about 40 Hz now with my newly
calibrated BC-221 (regulated 6.0 VDC filaments)
Why I am doing this, I have no idea!! I think it has something
to do with the sacrifice and dedication that so many people had in
the war years. It was an all hands on deck attitude that seems to
be missing today. A lot of effort went into the freq meters and
they were a large part of what happened when things went smoothly!
Dave K1WHS