I found some crystals labeled NDK020, 2.000 at the surplus store recently. Finally got around to trying them in 12AU7 circuit and they work at 2MHz. Crystal from plate to grid, 50K grid to gnd, cathode gnd, and an inductor in the plate to B+. That is what I saw in the text book.

They might be useful in a marker generator, as is, at 2MHz or better yet with a multiplier at 10MHz or half the frequency at 1MHz.

Can someone suggest a circuit that would do this? Can a multiplier jump five times in one stage or a divide by two would be a flip-flop?

I know the Hikock 288X has a 1MHz crystal oscillator that has a 10MHz harmonic by just changing the inductor connection. The 10MHz performance is not very good.

I got the crystal to work with a B+ of 50volts. Little cautious about going too high.

Lyn

I'm no 'expert' in this area but, during research, most of the multipliers I see are doublers and triplers. Anyway, here's an article on their operation.http://jlandrigan.com/files/FREQUENCY%20DOUBLERS%20understanding%20aids%20in%20tube%20operation.pdf

Multivibrators can be used to divide, of course. Here's a generic example. http://www.vias.org/basicradio/basic_radio_31_11.html

More in keeping with the 'analog world' is using an injection locked oscillator to divide. I've got a pdf on it but can't figure out where I got it. Basically, though, an oscillator will tend to 'sync' with another if the signal is large enough and near enough the fundamental or a harmonic so it basically consists of creating a free running osc at (near) the desired frequency and injecting the primary osc signal so the second 'locks' onto it. I was investigating that idea while contemplating an FM stereo multiplexor and the basic circuit can be found at the bottom of this page. http://flipperhome.dyndns.org/FM%20Stereo.htm The 'divide by two' is on the right side or the schematic.

Yes you can pull off the 5th harmonic with a resonant plate circuit but the conversion efficiency and spectral purity will be terrible. Also the resonant tank circuit components will cost more than a new 10 MHz crystal.


bruce

Speaking of stereo multiplexers, the first one, RCA BTS-1A, used the same divider circuit. http://fmamradios.com/pics/BTS-1A-sch.jpg It's "V2" in the top middle.

Thanks for the information. Plenty reading to do now.

The coil on the 288X was broken near the solder terminal. I managed to repair it and it works good on the 1MHz but not good on the 10MHz. If and when I get to it, I will add a dedicated 10MHz oscillator circuit.

Thanks again,
Lyn