In article ,
budgie wrote:

I'm told that 'zero beating' typically has accuracy not much better than some
tens of Hz due to the limited lower frequency response of the human ear... has
anyone tried zero beating a signal from above and below and taking the average
to get what might be a more accurate frequency estimate?

When the frequencies are close, a CRO is a great zero beat detector.

Yup.

It's a bit easier if your crystal happens to be on a frequency which
lets you zero-beat against an AM-modulated carrier signal, such as WWV
(during the early part of each minute, when it's sending a tone
burst). You don't have to try to pick out the beat frequency
directly... instead, you listen for the tone to waver in and out, and
tweak for the slowest wavering.

It's not hard to get the zero-beating accurate to within 1 Hz or
better with a bit of patience.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!