[time-nuts] wwvb weak on east coast especially when the pre-amps under water.

Joseph M Gwinn gwinn at raytheon.com
Mon May 14 22:01:01 UTC 2012





time-nuts-bounces at febo.com wrote on 05/14/2012 05:04:13 PM:

> From: paul swed <paulswedb at gmail.com>
> To: Discussion of precise time and frequency measurement <time-
> nuts at 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-bounces at 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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