The BC-221 was mentioned in a Time-Nuts thread from December, 2015. Copying from my post in that old thread:
Back in the early 1970's I took my BC-221 and added a TTL divide by 1,000 (or 2,000 or 4,000 or 8,000) external circuit to generate very precise audio test tones from the RF oscillator. The BC-221 had two output frequency ranges: LOW: 125 to 250 kHz HIGH: 2 to 4 MHz By using the appropriate range and divide ratio I could generate 15.625 Hz to 4 kHz (and multiples) with very smooth continuous tuning and great accuracy (typically better than 0.005%). This was very useful for adjusting and measuring audio filters and circuits, such as 2125/2295 Hz AFSK terminal units I was using on 2 Meter AM and with SSB rigs for HF FSK. I could tune up my filters built with 88 mH telephone surplus toroidial inductors. I could also use the audio source to compare by ear the beat note between harmonics of my divided-down 5 MHz commercial surplus precision oven oscillator and RF signals (such as during the ARRL Frequency Measuring Test). The anti-backlash gear mechanism, large dial with high resolution interpolation scale, and well-built variable capacitor were difficult to find in other commonly available radio related equipment. In my opinion the BC-221 was a technically beautiful precision instrument. It was the time-nuts tool of choice for several decades! -- Bill Byrom N5BB On Sun, Feb 12, 2017, at 08:31 PM, Bob Camp wrote: > Hi > > If you look at a typical BC-221 in use, it goes from “calibrated” in a > nice warm hut to the back > of a jeep. It heads out to an ice cold flight line and the > switch turns > the batteries back on again. > It bumps in and out of a batch of B-17’s setting each one up for the > day’s net frequencies. You > would be doing very well to hold 50 ppm under those > circumstances. That > was indeed adequate > for the purpose. > > Bob > > >> On Feb 12, 2017, at 7:58 PM, Bob Albert via time-nuts <time- >> [email protected]> wrote: >> >> Well 5 cycles per second is more than accurate enough. That >> translates to a 150 Hz error at 30 MHz, definitely negligible for the >> uses of all these gear. There was no official Time Nuts group at the >> time, although many of us had the spirit. Yet the capability of the >> BC-221 far exceeded its specification if you could receive WWV. >> >> I noted immediately that zero beat of WWV at 5 MHz was not as precise >> as at 15 MHz. In those days there was even a 30 MHz WWV but it got >> shut down a long time ago. And there were CHU and JJY. >> >> Bob >> >> >> On Sunday, February 12, 2017 4:02 PM, Dan Rae <[email protected]> >> wrote: >> >> >> To put BC-221 things in perspective, the 1 Mc/s reference crystal was >> adjusted, according to the manual, to within 5 c/s... >> >> Things have come a ways since! >> >> Dan >> >> >> _________________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> >> _________________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _________________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
