[time-nuts] GPS failure...

Arnold Tibus Arnold.Tibus at gmx.de
Tue Feb 7 16:47:59 EST 2006


> --- Ursprüngliche Nachricht ---
> Von: Magnus Danielson <cfmd at bredband.net>
> An: time-nuts at febo.com
> Betreff: [time-nuts] GPS failure...
> Datum: Mon, 06 Feb 2006 21:43:09 +0100 (CET)
> 
On Mon, 06 Feb 2006 21:43:09 +0100 (CET), Magnus Danielson wrote:

> 
> Today the little mystery of why we lost the GPS signal at work finally
> explained itself. Hooking up my Z3801 instead of our normal house-clock
> did not
> give any better result. So, today I finally said the antenna goes down for
> inspection. I had been given the hint that it might have some humidity in
> it,
> so I tossed it into one of our climate owens for a nice little steam-off.
> Instead it proved to be a gentle defrozting action. There was not high
> humidity, it was a whole little splash of water in there, you heard it as
> you
> shaked it. That besides finding a spider in the lower-cap, it had eaten
> half
> the o-ring on the outside and near the contact we also found its pray
> wound in.
> 
Hello Magnus,
was there no small hole on the lower side, underneath, 
was it blocked by the little spider?

Offshore working with meteorologic sensors and electronics, 
I experienced personally that it is not a very good idea to build 
antennas or other electronic devices into hermetic cases 
without a breating hole in it (well protected against rain and 
drops of water, possibly contain a filter device) unless the case 
is not pressure cycling proof, including cables and connectors. 

Due to temperature and air pressure changes, 
these devices are breathing air with humidity via the connectors, 
coaxial and other cables, which in colder phases is condensing 
and remaining inside, that way filling up the box, drop per drop.
 
The 2nd way is to build a real pressure proof box with hermetic 
feed through connectors (glass or ceramic insert, O-ring sealed), 
capable to withstand more than 1 meter of water immersion.

Good luck and have fun,

Arnold, DK2WT

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