[time-nuts] LF Xtals

Geoff Blake geoff at palaemon.demon.co.uk
Tue May 20 13:29:04 EDT 2008

>     Hi,
>     I just found a 1000c/s (yes 1kHz) quartz crystal at a local radio car
>     boot sale. It's a NOS GEC "Quartz Crystal Unit" type DJC/669. It's in
>     an overlength minature valve (tube) glass envelope. The crystal is a
>     long slab with 3 connections. The 3rd connection seems to be a small
>     (feedback?) electrode.
>     What's the lowest frequency crystal made? Anyone have any suggestions
>     for an oscillator circuit?
>     Robert G8RPI.

Well, I know 1kHz and 440Hz are rather esoteric, but (IMV at
least) a 4kHz xtal is less of a rarity. Such a xtal was fitted to
Tek 560 series 'scopes and divided by 4 to provide a 1kHz
calibrator signal. The xtal was fitted in a HC6U form can that was
about 3 inches long.

The calibrator was switched off in normal useage as the 4kHz whine
from the xtal was quite annoying. I built a RTL logic digital
clock using one, but could never get it better than several

    Geoff Blake G8GNZ      located  near  Chelmsford,  Essex,  U.K.
    Please reply to:      geoff(at)palaemon(dot)demon(dot)co(dot)uk
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