[time-nuts] EOL Motorola Oncore Remote Antenna

[jimlux]

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 <phk at phk.freebsd.dk>
> Sent: Sunday, November 29, 2020 11:19 PM
> To: Discussion of precise time and frequency measurement <time-nuts at lists.febo.com>; Art Sepin <art at synergy-gps.com>
> 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.
>