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nielskock(at)get2net.dk
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 Posted: Tue Jul 18, 2006 12:42 am Post subject: GPS interference-again |
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In spite of being a member of the Europa Club since its birth I am a newcomer on the forum-scene.
What prompted me to enter this scene is interference problems twixt my Skymap IIIC and my KX125 radio.
Similar problems, I can see from browsing the archive-index, have been discussed between Bryan Allsop and
Fred Fillinger a year ago, but there is some mysterious (to me) variation in my case which I hope that Bryan or someone else
might be able to advise me about. But, please, slowly. I'm extremely dim-whitted.
The problem, a chainsaw-like noise in the headphones when the GPS is on, presented itself already in the distant past
with a Skymap-I, mounted in my Pa28. The solution was easy: I sold the Piper, GPS included. Then built my present Europa
in which I mounted a Skymap II. All was bliss, until the noise after 3-4 years recurred. Yes, after 3-4 years! And only on some
frequenses, 119.52 where the interference was in bursts, and 118.5 ( and a few others), where the noise was continuous.
The Skymap II was then replaced by the IIIC. Ah, peace and quiet again - for a while- until the problem recurred. First on the
old 119,25 (my home base), then increasingly on many other frequenses, predominantly in the lower half range.
As with Bryan receiving and transmitting cancels out the noise more or less, but not intercom, and it is absolutely enough to
render you insane and deaf. The interference also vanishes when the GPS is removed from the panel and strapped to my
thigh, but that is a bit awkward.
The antenna line to the GPS runs from the spine of the Europa forwards under the left door to the panel, and the one to the
Radio along the right hand side of the aircraft. The antenna coax to the radio (and the TXP) are rather long and are coiled-up
inside the right hand side of the panel. Further, it doesn't matter whether I use the fixed antenna or a loose one on top of the
panel.
My friendly avionics Wizart at Billund has after much head-scrtatching applied a choise of his wizardry to the problem:
Making sure that connections on the GPS-coax are OK, even surrounded said connection with some foil-like screening-material,
decreasing the squelch of the radio, applying some ferrite-pearls on the individual leads of the power-lead to the GPS, all to
no avail. He has also expressed thoughts about some electronic component in the GPS being ailing after some years' use.
The owner of a neighbouring helicopter-company whose helicopters use the Skymap IIIC too, had the same problem which,
so he told me, was found to originate from the blower in the GPS due to Worn bearings. Be that as it may, the Skymap I and
II do not have blowers, and were still beset with the problem!
It may well be an antenna/screening problem. But why does this problem arise after a some years' impeccable service, and
then seem to increase?
Can anybody help with an explation which even I might grasp, and a solution?
Niels Kock,
Odense, Denmark
OY-ODA
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Gilles.Thesee(at)ac-greno
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| Posted: Tue Jul 18, 2006 1:12 am Post subject: GPS interference-again |
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Niels Kock a écrit :
| Quote: | ...
It may well be an antenna/screening problem. But why does this problem
arise after a some years' impeccable service, and
then seem to increase?
Can anybody help with an explation which even I might grasp, and a
solution?
Niels,
|
Please remember that shielding is not a one-size-fits-all solution to
audio noise problems. It only works for specific cases. Many many times
it has something to do with proper grounding.
The appearance after some time may indicate a wiring related issue.
Are all your grounds properly connected at a unique point of the firewall ?
Is your intercom corrrectly wired ?
Why do you have a long coax run for the radio ? Why not shorten it and
(at least) gain on the signal attenuation ?
Are your antennas sufficiently remote from each other ?
Have you tried running each of the suspected device from a completely
separate power source (battery), to ascertain the radiated or conducted
origin of the problem ?
Since the noise seems to be related to some specific frequency ranges,
have you considered adding a notch-filter to your radio ? The Garmin
400-series call for a check of the VHF entire frequency range and the
addition of a 1.547 GHz notch filter at the rear of the radio in case of
interference problem.
Regards,
Gilles Thesee
Grenoble, France
http://contrails.free.fr
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Brian Davies
Joined: 10 Jan 2006
Posts: 124
Location: uk
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| Posted: Tue Jul 18, 2006 3:51 am Post subject: GPS interference-again |
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Neils,
It might be worth a phone call to Skyforce in the UK. Although they are part of Honeywell the unit is built in a small factory near Chichester in the south of England. I have always found them very helpful. Their number is +44 1243 783763.
Brian Davies
From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of Niels Kock
Sent: 18 July 2006 09:34
To: europa-list(at)matronics.com
Subject: GPS interference-again
In spite of being a member of the Europa Club since its birth I am a newcomer on the forum-scene.
What prompted me to enter this scene is interference problems twixt my Skymap IIIC and my KX125 radio.
Similar problems, I can see from browsing the archive-index, have been discussed between Bryan Allsop and
Fred Fillinger a year ago, but there is some mysterious (to me) variation in my case which I hope that Bryan or someone else
might be able to advise me about. But, please, slowly. I'm extremely dim-whitted.
The problem, a chainsaw-like noise in the headphones when the GPS is on, presented itself already in the distant past
with a Skymap-I, mounted in my Pa28. The solution was easy: I sold the Piper, GPS included. Then built my present Europa
in which I mounted a Skymap II. All was bliss, until the noise after 3-4 years recurred. Yes, after 3-4 years! And only on some
frequenses, 119.52 where the interference was in bursts, and 118.5 ( and a few others), where the noise was continuous.
The Skymap II was then replaced by the IIIC. Ah, peace and quiet again - for a while- until the problem recurred. First on the
old 119,25 (my home base), then increasingly on many other frequenses, predominantly in the lower half range.
As with Bryan receiving and transmitting cancels out the noise more or less, but not intercom, and it is absolutely enough to
render you insane and deaf. The interference also vanishes when the GPS is removed from the panel and strapped to my
thigh, but that is a bit awkward.
The antenna line to the GPS runs from the spine of the Europa forwards under the left door to the panel, and the one to the
Radio along the right hand side of the aircraft. The antenna coax to the radio (and the TXP) are rather long and are coiled-up
inside the right hand side of the panel. Further, it doesn't matter whether I use the fixed antenna or a loose one on top of the
panel.
My friendly avionics Wizart at Billund has after much head-scrtatching applied a choise of his wizardry to the problem:
Making sure that connections on the GPS-coax are OK, even surrounded said connection with some foil-like screening-material,
decreasing the squelch of the radio, applying some ferrite-pearls on the individual leads of the power-lead to the GPS, all to
no avail. He has also expressed thoughts about some electronic component in the GPS being ailing after some years' use.
The owner of a neighbouring helicopter-company whose helicopters use the Skymap IIIC too, had the same problem which,
so he told me, was found to originate from the blower in the GPS due to Worn bearings. Be that as it may, the Skymap I and
II do not have blowers, and were still beset with the problem!
It may well be an antenna/screening problem. But why does this problem arise after a some years' impeccable service, and
then seem to increase?
Can anybody help with an explation which even I might grasp, and a solution?
Niels Kock,
Odense, Denmark
OY-ODA
--
No virus found in this incoming message.
Checked by AVG Release Date: 14/07/2006
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nielskock(at)get2net.dk
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| Posted: Tue Jul 18, 2006 4:37 am Post subject: GPS interference-again |
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It can never hurt. I might just do that.
Thanks for your reply, Brian.
Kind regards,
Niels
[quote] ---
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nielskock(at)get2net.dk
Guest
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| Posted: Tue Jul 18, 2006 4:53 am Post subject: GPS interference-again |
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Thank you for your reply, Gilles.
A wiring-problem certainly is worth looking into, especially taking the
course of events into consideration. I shall
give the grounding and other wiring a hard look.
The GPS and Radio antenna are almost as far from each other as possible.
Still, it could perhaps be improved.
Also, I shall try to power the GPS from a surplus battery while it is
mounted in the panel, that would be an
easy test.
Finally, I will talk with my avionics-man about the notch filter.
If, and hopefully-when the cause and remedy is found I shall reveal it
through the forum.
Best regards,
Niels
---
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