Re: OT: sound speed depends on frequency on mars

On 2/09/2024 12:27 am, john larkin wrote:

On Sun, 1 Sep 2024 15:34:13 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
 

Meander-line sections connected by loading coils could be interesting.
One product that I'm considering now is a programmable delay line, and
that idea might help.

>
Like the MC100EP195?
>
https://www.onsemi.com/pdf/datasheet/mc100ep195-d.pdf
>
You do seem to spend a lot of time re-inventing the wheel, and
congratulating yourself on the originality of your re-invented concepts.

 I've tested that part. It's expensive, drifty, and has an insane
amount of jitter. It's funny that its resolution is "about 10 ps"

It's resolution is about 10psec, because that's the - temperature dependent - delay through individual delay elements. If you want it to be more precise, you have to control the part's temperature, or re-calibrate every few minutes. That's what I was planning to do when I contemplated using it, and figured that I could get it done within a millisecond - which did call for a fast A/D. Which one I can't remember because it was back in 1998.
The RMS random clock jitter is specified on page 10 of the data sheet, and it's around 1psec which pretty standard for ECL parts - not remotely insane.
The nice thing about ECL is that it doesn't mess up it's power rails in the way that CMOS and TTL do, which does get rid of one jitter source.
I once got rid of some nasty sub-nanosecond jitter on a TTL clock by generating it in ECL (run between 0V and -4.5V) and getting it
out of an ECL-to-TTL converter.
I had expected the ECL-to-TTL converter to be equally susceptible to noise on the +5V rail, but I was happy to find out that I was wrong.
--
Bill Sloman, Sydney

Maxim and I think someone else made CMOS programmable delay line
chips, which were equally bad, not to mention discontinued.

The MC100EP195 and MC100EP196 have been around for thirty years now, and don't seem to have been discontinued.

We mostly use fast ramps and comparators and DACs to make programmable
delays. Jitter is low and polynomial calibration makes them very
accurate. Cheap too.

Been there, done that.

Of course I keep inventing things. That's my job.

You'd have to do it less often if you knew more about what was already available, and were more skilled at reading the datasheets for the stuff you could buy.
Inventing stuff is fun, but nobody sane does it when they don't have to.
--
Bill Sloman, Sydney