[time-nuts] Low frequency crystal

[Alan Melia]

Hi Robert in the days before TTL dividers there were quite a few vert low
frequency cuts. I think that one is a flexural bar designated "NT cut". I
have also seen crystals of lower than that made in the "gapped ring" format
which oscillate a little like a tuning fork. ( I think I have seen one of
these cut for 440Hz, but a 1Khz gapped ring would fit in an Int. Octal GT
envelope.)

I think on your sample the supports are about 25% of the distance from the
ends. these are the nodes of the mechanical vibration. You may well be right
about the extra excitation electrode. These big chunks of quartz are quite
difficult to get moving I believe. Their stability is nothing special but is
a lot better than any other form of electronic resonator at the time. It
probably dates from the early 1950s.

Alan G3NYK


----- Original Message -----
From: "Robert Atkinson" <robert8rpi at yahoo.co.uk>
To: <time-nuts at febo.com>
Sent: Tuesday, May 20, 2008 1:32 PM
Subject: [time-nuts] Low frequency crystal


>
>
>     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.
>      __________________________________________________________________
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