Null fundamental of tuning-fork crystal

I'll play around with trying to lock a regular Colpitts to an overtone for s**ts and giggles, but I won't spend forever on it.

Probably won't be able to.

the

Of course. The acoustic modes extend all the way up to optical phonons.

Mass-spring resonances don't exhibit overtones near harmonics of the lowest

-order mode. Simple ones don't exhibit higher resonances at all, unless the spring has mass or the mass has springiness. ;)

Cheers

Phil Hobbs

It's easy to blow overtones on a beer bottle, jug, length of pipe, or whatever. For low notes you blow lots of air at low pressure mostly perpendicular to the direction of the hole. For higher notes you blow higher pressure air through a smaller opening in your lips, more downward toward the far edge of the lip of the hole. Experiment around -- you should be able to easily find at least one overtone, and with experience you can get four or five different note out of the bottle before you either get tired or your housemates rip you to shreds.

Solartron 7081 "eight nines" DMMs use a 4046's type 2 phase detector to lock ~5MHz to the mains. They don't use the 4046 oscillator, preferring their own varactor-based oscillator.

The metal-gate 4046 is a nice part in its way. Every single one of the various HC versions (HC4046, HC7046, HC9046) has a horribly broken oscillator--each broken in its own perverse way. I use PD2 of the HC4046 a fair amount, either as the main phase detector or (more often) as an acquisition aid for a quieter PD such as a Mini Circuits MPD-1.

Cheers

Phil Hobbs

I came up with this last night. I get the 4093 or similar for "free" because I already need it to make the crystal oscillator, and I also already need the binary counter.

Two sections of the 4093 and two diodes make a ring mod to get the DC difference freq, one side being fed by the output of the watch crystal oscillator, the other by a divide by four. Then into a TL431 as an integrator, feeding the 555 CV pin. So it frequency-locks to the 4th harmonic of the crystal frequency.

It looks good in the sim; R1/C1 and C3/R6 will need tuning though. It draws about 5mA, which is fine. A TL431, 555, same-value resistor network and a couple diodes and ceramic caps should be under 20 cents even in singles, whoopee!

I could use the output pin of the 555 to make a low-current negative supply, too.

AFAIK, no one makes a "single-gate" version of the 4046 with just the phase detector -- which is a shame, because there's a lot of applications out there that use just that, and waste a lot of space with the rest of the chip.

Which is always the case, no?

... or the Young's modulus of the spring varies with stress.

That's a nonlinearity, though, not a higher-order mode.

Cheers

Phil Hobbs