Check frequency

Look up 'Lissajous'. The proposed experiment is to use a frequency-shifting transformation, i.e. to look at a beat frequency against a known frequency standard. The standard would (best) be an atomic fountain or (more practical) rubidium-beam or (more common) aged calibrated crystal clock (not AT crystal, more likely GC or other exotic type). A common frequency counter might have an ovenized oscillator, but not 'reference-standard' precision. If one were able to calibrate a warmed-up counter for a day or so against NNTP time, it might suffice for seven-figure accuracy. Or, it might not.

No, that confuses the accuracy of the small-frequency beat with the accuracy of the larger frequency that one has applied (X-axis) to the reference (Y-axis). They aren't proportional. 'ppm' measurement of one doesn't tell the 'ppm' value of the other.

The timebase of a common frequency counter IS a hard limit, in the sense of your 'ppm' calculation, to the accuracy of its measurements.

"John Fields, Autistic "

Is the great JF completely ignorant of a such a simple technique ???

Must be so - everything he says screams it.

Here is the idea:

" If you have a suitable reference frequency source, you can watch the pretty Lissajous figure on an X/Y oscilloscope (no dual channel, no counter) and if it goes through a cycle in 100 seconds, with 0.1 second stopwatch accuracy, you've just made a frequency measurement with

A frequency counter is a convenient and quick solution, but it is NOT required nor is it superior in accuracy. "

The demented JF has forgotten how to think analogue.

Cos he has forgotten how to think at all.

.... Phil

"Clue Less = John Fields "

This is all too weird for me.

..... Phil

use a tuned probe. 32768Hz crystals work good for probes.

What I wrote, was that one could watch a Lissajous pattern evolve and time it with a stopwatch with 0.1 second accuracy. A stable pattern indicates exact small-integer-ratio frequency matching, and an evolving pattern indicates a deviation from the match.

So, for someone working with a trimmer, you get immediate visual feedback when looking at a Lissajous display, and the trim is quickly done. If there's a drift, as I described, you can use simple easily available tools (a stopwatch) to achieve quite remarkable precision. That '.001 Hz' was not a joke, nor an error.

As to the accuracy of the 'reference', it was my thought that a crystal out of the box would have 5 figure accuracy, maybe 6, and that trimming it would require a reference with much more than that (8 figures being a good high target). My frequency counters aren't that good, and the required gate times aren't friendly to tweaking-as-you-watch even if they were.

I believe tuning-fork watch crystals are trimmed at the factory with laser ablation of the metal (mass) on the tines, and, with the recommended oscillator circuitry, should do well without any adjustment. Aging and temperature drifts which aren't trimmable are likely to be significant.

FOAD - septic f*****ad.

..... Phil

"John Fields, Autistic LIAR "

The great JF is completely ignorant of a such a simple technique.

Here is the idea:

" If you have a suitable reference frequency source, you can watch the pretty Lissajous figure on an X/Y oscilloscope (no dual channel, no counter) and if it goes through a cycle in 100 seconds, with 0.1 second stopwatch accuracy, you've just made a frequency measurement with

A frequency counter is a convenient and quick solution, but it is NOT required nor is it superior in accuracy. "

The demented JF has forgotten how to think analogue.

Cos JF has autistic dementia and cannot think at all.

.... Phil