Guys,

If you’re bound determined to bring a 1942 or so BC-221 frequency meter into the 21^st Century by generating a calibration book, at least make your job a little easier.

Use either Microsoft Excel or one of the many clones available  on the internet to store the results. Although I haven’t downloaded it, there is a ready-made BC221 spreadsheet available on the internet at https://www.royalsignals.org.uk/files/221/bc221cal.htm.

Unless you already have a frequency counter, invest in one of the many “cheap and dirty” counters available on eBay.

Couple the output of the BC-221 to the counter with a 100  pF  capacitor.

Fire up the BC-221 in the environment where it will be used, turn it on, and let it sit there for 3 or 4 hours.

By the way, the calibration crystal can be “tweaked.” On my 221 you access the crystal trimmer by removing the nameplate on the front panel.

73,

/Miles, K2CBY