Thanks for correction Will
On 30/12/15 17:12, Bill Byrom wrote: > I believe you meant a BC-221 frequency meter, which was a very good > instrument when introduced over 70 years ago:. > http://radionerds.com/index.php/BC-221 > http://www.orionsword.net/Electronics/TestEquipment/ZenithFreqMeter/BC221.html > > 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 Tue, Dec 29, 2015, at 08:12 PM, Will wrote: >> >> That sure beats a BC21 that many hams (and Post Office Techs) used long >> ago. >> >> So long ago Google doesn't want to help and memory has faded over half >> a century. >> >> Cheers, >> Will >> > > _______________________________________________ > 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.
