[time-nuts] Question on crystal jumps

[Ron Smith]

Hello Antonio,

A.W.Ladner and C.R.Stoner in their book "Short Wave Wireless Communication"
describe a phenomenon called "stepping", which may be the same effect as the 
jumps you are
investigating.

The book is quite old, 4th edition published in 1942 by Chapman and Hall,
and refers (on page 321) to stepping in X- and Y-cut crystals, which may not
be common these days, but perhaps crystals of all cuts are affected to some 
degree.

The text says the curve of frequency against plate thickness does not give a
straight line, but has discontinuities in it. These discontinuities they
call "stepping points" and are a result of edge vibrations coinciding with
sub-multiple frequencies of the wanted thickness vibration mode. The degree
of coupling between the wanted and unwanted modes varies with crystal
dimension. If there is zero coupling, the stepping points should not affect
the main oscillation. But perhaps even the smallest change in dimension can
cause it to cross one of these discontinuities and jump to and fro? I
suspect that crystal sensitivity to stepping or jumping may be correlated
with its temperature coefficient, although there are other factors
(including gravitational) that influence frequency of oscillation at very
small levels.

Antonio, these frequency jumps are not a phenomenon I have come across 
myself, so I have nothing to log,
but I am interested in what you discover. Wouldn't it be fascinating if you 
discovered a global trigger to many simultaneous frequency steps?
The book reference is a bit old I'm afraid - things have moved on since 
1942.
Good luck.


Ron Smith
G3SVW




----- Original Message ----- 
From: <iovane at inwind.it>
To: "time-nuts" <time-nuts at febo.com>
Sent: Wednesday, October 22, 2008 11:06 PM
Subject: Re: [time-nuts] Question on crystal jumps


> Hi Rick
>
>> I'm not quite sure what the question is here....
>> ....
>
> The question is:
> may anybody tell me (date and time) when a crystal jumped?
> (a sample response could be: my crystal jumped on January 22, 2006 12:25 
> UT).
>
> I would like to map in time as many jumps as possible.
>
> I hope someone in the list has a log of his jumps.
>
> Thanks and 73,
> Antonio I8IOV
>
>
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