time-nuts-boun...@febo.com wrote on 05/14/2012 05:04:13 PM:
> From: paul swed <paulsw...@gmail.com>
> To: Discussion of precise time and frequency measurement <time-
> n...@febo.com>
> Date: 05/14/2012 05:04 PM
> Subject: Re: [time-nuts] wwvb weak on east coast especially
> when the pre-amps under water.
> Sent by: time-nuts-boun...@febo.com
>
> Magnus is right lots of ways for water to sneak in.
> So I have not had time to figure it out yet. But it is a copperloop and I
> suspect the place it's joining the preamp box lets water in over time.
The
> fact is even a small pin hole that allows air in and out that's humid can
> allow water buildup.
Atmospheric pressure variation, even without wind pressure, is about +/-
10% at the extremes, and it's essentially impossible to make ordinary stuff
hermetic enough to prevent breathing. The classic dodge is to connect a
long tube to the enclosure, with the tube having sufficient volume that the
breathing is restricted to the tube. Or, have the tube connect to a
conditioned space, like the house. Then, the inevitable small leaks no
longer matter as the tube equalizes the pressure.
The extreme example of isolation using a tube is Pasteur's swan neck flask.
<http://en.wikipedia.org/wiki/Louis_Pasteur>
Modern outdoor enclosures use a filter of some kind, but the underlying
principle is the same.
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