Jim Thompson wrote:

On Fri, 06 Nov 2009 19:03:53 -0500, "Michael A. Terrell"
wrote:


Jim Thompson wrote:

On Fri, 6 Nov 2009 20:53:53 -0000, "ian field"
wrote:

[snip]

Can't I just make a PLL lock on to the frequency and stay put after the note
has decayed, then measure the frequency with a digital frequency counter?


A PLL that doesn't drift once it loses reference ?:-)


yeah. A Pathetic Locked Loopy.

I suppose you _could_ put a sample and hold on the control voltage,
but my experience with _good_ PLL's is that it takes around 100
reference cycles to ensure accuracy, _before_ you could "coast".

I think it should really be done with a high speed counter to get
signal period.


I would use period measurement. I had to for the multi second AGC
integration in the telemetry systems I worked on. The PLLs I worked
with were in the 360 to 540 MHz range, with multiple band segments that
overlapped.


--
The movie 'Deliverance' isn't a documentary!