[time-nuts] Thunderbolt stability and ambient temperature

Dave Baxter dave at uk-ar.co.uk
Mon Jun 15 05:44:31 EDT 2009


Hi All...

Some interesting semi off topic discussions of late, very interesting.

Re the water in plastic bottle problem.  (I seem not to have seen the
original message, there again we've had transient email/isp problems
here recently)

A "Vacuum" formed by any migration of the contents will not distend
(expand) a bottle, but will cause it to collapse in on itself.  Water
and plastic container combinations in general can be interesting, if
just due to the process of Osmosis, dependant on the contents and
container materials.  (Ask any owner of an elderly GRP boat about that!)

Water and some metal combinations are known problem points too, unless
you use extremely pure water and choose your metal (and closure methods)
carefully.

I also suspect a good quantity of light grade synthetic or silicone
based oil would do almost as well, and be electrically inert and not
react with the container or the materials used in the electronics, so
long as the exact material used was chosen with care.  However, it will
take a system much longer to reach thermal equilibrium, the larger the
thermal mass it has.

Or as someone else suggested, use a Glass container.   So long as you
don't want it to last for many 100's of years, as Glass is not a solid,
it is a "super cooled fluid" and as such it flows like Ice over time,
just that it takes much much longer to do so!  Oh, and make sure it has
some thermal expansion relief (a gas pocket or an intentional
"mechanical soft spot")  Just a thought.

I remember hearing of a UK amateur many years ago, who had a remote
tuneable VFO for (I think for 80mtrs) buried some feet underground in
his garden, to achieve thermal and frequency stability.  And that was
using Valve (Tube) technology too!   It was powered 24/7 of course, but
I do not know any other details.   However, it was said that his signal
was one of the most stable (frequency wise at least) on the band in
those days (the 70's if not the 60's)   I do not know how it was
remotely tuned, and it's not exactly a portable solution either!

Regards to all.

Dave B.








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