[time-nuts] Vintage Frequency Measurement

[jmfranke at cox.net]

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 <alan.melia at btinternet.com> 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" <time-nuts at febo.com>
> To: "Discussion of precise time and frequency measurement" 
> <time-nuts at febo.com>
> 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 
> > <namichie at gmail.com> 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 <scott.j.stobbe at gmail.com> 
> >> 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?
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