On 11/30/20 1:22 PM, Art Sepin wrote:
To me it looks more like water ingress through micro-cracks in the
plastic-dome, and the O-ring did its job and kept that water in.
Interesting. That's the first we've heard about micro-cracks in the Radome but that's
certainly a likely possibility with such a long exposure to U/V. The more common failure
mode reported was moisture ingress due to "breathing;" the uptake of moisture
laden air past the O-Ring, due to a small pressure differential. But, once the moisture
was inside, it was also trapped internally by the O-Ring. This condition was reported
more often in geographic areas that experienced a wide variation in barometric pressures.
Art
I'll bet pressure changes inside the "sealed" radome due to temperature
changes are bigger than those due to local barometer changes.
But an interesting thing - water vapor will go through cracks, porosity,
that liquid water will not. The commercial success of GoreTex is an
example of this, but cracks, o-rings that aren't quite right, etc. are
also ways it can happen.
Making a truly hermetic box is hard.
-----Original Message-----
From: Poul-Henning Kamp <[email protected]>
Sent: Sunday, November 29, 2020 11:19 PM
To: Discussion of precise time and frequency measurement <[email protected]>;
Art Sepin <[email protected]>
Subject: Re: [time-nuts] EOL Motorola Oncore Remote Antenna
--------
It's obvious from the photo that the O-Ring seal failed its purpose
over its many years of service. Has the unit totally failed or does the
electronic portion still function?
No, the electronics is stone dead.
To me it looks more like water ingress through micro-cracks in the
plastic-dome, and the O-ring did its job and kept that water in.
The microcracks are uniform and seem to follow the molding flow, and that is
probably to be expected in our climate: We have a lot of humid freeze-thaw
cycles.
I wonder if buffing the radomes with car-wax would help ?
I said lucky because I found some GSynQ parts here in an engineering
storage cabinet that we can send to you at no charge to revive your unit.
Thanks for the offer, but dont bother: I had a spare on hand, and I may still
have third one lying around somewhere.
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