Looks like I was able to reference your use of the three-oscillator technique and highlight the history of the technique just minutes before your email to the Time-Nuts Newsgroup. I originally referenced your successes in "Accurate Zero Beating Using the Three-Oscillator Method," QST, Hints & Kinks Column, Vol. 94, No. 8, August 2010, p. 59.
John WA4WDL ---- Alan Melia <[email protected]> wrote: > I am surprised no-one mention the 3-beat method, which was fairly common for > Hams with comms receivers. You put the BFO on and adjusted so the main slow > beat modulated the level of the output tone. You can judge zero beat to much > better than 0.1Hz that way probably near as low as 0.01Hz. (1E-9 for 10MHz > !!) > > Lissajous figures are not ideal either but don't require a comms receiver, > (but do require a 'scope with X-Y facilities :-)) ) a better technique > certainly for fixed frequencies (stand comparison) uses Z-mod on the scope > or a running "toothed wheel" display see Radio Laboratory Handbook by > Scroggie. > > Ah and the BC-221...... > > Alan > G3NYK > > > > ----- Original Message ----- > From: "Bob Albert via time-nuts" <[email protected]> > To: "Discussion of precise time and frequency measurement" > <[email protected]> > Sent: Sunday, February 12, 2017 5:00 PM > Subject: Re: [time-nuts] Vintage Frequency Measurement > > > > First you need a standard, a crystal oscillator. If you want serious > > precision, you'd have one in an oven. Zero beat that with WWV. Then make a > > very stable VFO and calibrate the harmonics against the crystal. Assume > > linear calibration on the VFO between check points. > > The military LM and BC-221 were very good units. I had one. The check > > points in the calibration book were too far apart but there were others > > that weren't documented that would make for more precise calibration. > > I also built a frequency meter that was amazingly accurate, from a GE Ham > > News project printed back in the early 1950s. It used a VFO that went > > between 100 kHz and 101 kHz for its full range, adjusted by a micrometer > > dial (military surplus). Its harmonics would be zero beat with the > > unknown. Using a successive number of harmonics would identify the > > harmonic number and the scale could be interpolated to within much less > > than 1 kHz over the HF range. > > Of course, zero beat was hard to identify so you could use an oscilloscope > > lissajous pattern (if you had an oscilloscope, which I didn't). What I did > > was turn up the volume and listen to the beat. When it got down near zero > > the sound of the AGC surging would tell me the frequency of the beat and I > > could adjust to make it stop surging. > > When I got my hands on a Beckman counter I was in heaven. > > Bob > > > > > > On Sunday, February 12, 2017 4:01 AM, Neville Michie > > <[email protected]> wrote: > > > > > > Back in the early sixties I worked in a lab adjusting filters for line > > transmission. > > We had numerous oscillators, built to be boat anchors, and CROs set up for > > X-Y display. > > The lab had 100hz, 1kHz, 10kHz standards wired in. > > We were expert at recognising lisajou figures. We might have several > > oscillators running together, > > and we could establish almost any frequency with precision. > > Calibting an oscillator would not have been difficult. > > > > Cheers, Neville Michie > > > > > > > >> On 12 Feb 2017, at 5:08 PM, Scott Stobbe <[email protected]> > >> wrote: > >> > >> I was inspired recently coming across a Lampkin 105 frequency meter, as > >> to > >> how frequency measurement was done before counters. > >> > >> Certainly zero-beating a dial calibrated oscillator, would be one > >> approach. > >> > >> Is there a standout methodology or instrument predating counters? > >> _______________________________________________ > >> 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. _______________________________________________ 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.
