GPS failure...
Dear fellow time-nuts,
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.
So, de-bug your antenna before you find it full of wild-life and water-life as
we found. This antenna is now de-comissioned and a new is being ordered
tomorrow. We will also take the oppertunity to mount it better, possibly even
at a different localtion, but that will probably have to wait until spring, as
we now have a little snow-storm, not he best situation for walking the
rooftops.
Hope you learned something. We learned that we need to check the waterlevel in
the GPS antenna regularly. I will also hack up a continous logging system so I
can get warnings when the signal fades away. I need that at home too anyway.
Cheers,
Magnus
You have re-discovered the meaning of the word debug.
On Mon, 6 Feb 2006, Magnus Danielson wrote:
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.
You did not mention the brand or model of the antenna you were using. I was
using a Trimble outdoor antenna for a year. Then it went dead after heavy rain.
I found water inside. I opened it and found that the epozy had failed to bond
the top shell to the bottom thoroughly, thus allowing water to enter when the
air pressure changed due to temperture extemes. I showed it to an engineer at
Trimble who completely dismissed the possibility that it was a problem with the
epoxy application. He insisted that I must have had water seep in through the
type N connector (which is completely on the bottom of the antenna and was
covered with heatshrink tubing)
From: Jeffrey Pawlan jpawlan@pawlan.com
Subject: Re: [time-nuts] GPS antenna failure
Date: Mon, 6 Feb 2006 14:08:54 -0800 (PST)
Message-ID: Pine.GSO.4.31.0602061403500.10028-100000@jeffrey150.pawlan.com
You have re-discovered the meaning of the word debug.
Well yes. ;O)
On Mon, 6 Feb 2006, Magnus Danielson wrote:
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.
You did not mention the brand or model of the antenna you were using.
I left it back at the office. It came with the GPS and was not a particular
choice of mine. It is not a Trimble thought.
I was using a Trimble outdoor antenna for a year. Then it went dead after
heavy rain.
I found water inside. I opened it and found that the epozy had failed to bond
the top shell to the bottom thoroughly, thus allowing water to enter when the
air pressure changed due to temperture extemes. I showed it to an engineer at
Trimble who completely dismissed the possibility that it was a problem with the
epoxy application. He insisted that I must have had water seep in through the
type N connector (which is completely on the bottom of the antenna and was
covered with heatshrink tubing)
I must admitt that waterproof methods is not one of my expertise areas. All of
a sudden I feel that I should learn more about it. :P
Cheers,
Magnus
--- Ursprüngliche Nachricht ---
Von: Magnus Danielson cfmd@bredband.net
An: time-nuts@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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From: "Arnold Tibus" Arnold.Tibus@gmx.de
Subject: Re: [time-nuts] GPS failure...
Date: Tue, 7 Feb 2006 22:47:59 +0100 (MET)
Message-ID: 4866.1139348879@www092.gmx.net
Hello Magnus,
Hi Arnold,
was there no small hole on the lower side, underneath,
was it blocked by the little spider?
No, the hole I think was intended for that purpose was hidden under the label
giving away what manufacter and model-number it is.
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.
I think this device had one designed. But I suspect it was put out of action
by the label. :P
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.
Which is what I suspect this baby died off.
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.
Well, yes. Thing is, I'm not building them, I am just trying to use one or two
antennas.
Good luck and have fun,
Arnold, DK2WT
Thanks for the insight. It is along the lines of what I have a gut-feeling of,
but it is good to get confirmation.
Cheers,
Magnus