[Milsurplus] The BC-221N Freq Meter calibration.

[Bob Camp]

Hi

Based on the one example I’ve played with, the original BC-221 / LM calibration setup used the best frequency standard then available. I’d suggest that a high quality / calibrated standard would need to be part of doing this as well. 

Bob

> On Feb 4, 2024, at 2:53 PM, k2cby at optonline.net wrote:
> 
> Guys,
> If you’re bound determined to bring a 1942 or so BC-221 frequency meter into the 21st 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
>  
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