Hi Remi,
Panel mounted EFIS units with internal GPS antennas are prone to interferen
ce depending on installation.
I=92ve always used an external antenna in my practice. I mount them to a m
etal inverted hat shape to the top inside of the panel. Early WAAS GPS ant
ennas (those less expensive much lighter plastic type) work better when att
ached to a metal surface. The large, heavy Garmin types have a metal base s
o a simple fiberglass mount in the panel works OK. The Europa, being fibe
rglass, does not impede radio signals but the surrounding metal globs aroun
d these items do. The proximity of other receiver antennas for some reason
do not seem to bother one another. Go figure.
As far as antennas, I have always made my own BNC cables and connectors and
never have had a problem once ohmed out. RG 58/400 cable is fairly bulky
and are easy to make to proper length. Manufacturers normally resist allow
ing amateurs to modify their cables for obvious reasons, but if you have th
e tools and know how, shortening a cable is perfectly fine. I just prefer
to remake the cable completely. The small S type connectors and antenna wi
re, I coil up (because it is a small flexible wire) and I place the coil in
the panel away from the GPS antenna and all is fine as long as the coiled
antenna wire is not wound around the antenna. (I put mine along side the E
FIS unit as its metal case should prevent interference.) If you coil you
r antenna wire, just use care where you put the coil. Between the Garmin
/Blue Mountain/EFIS of choice and the altimeter has always worked for me.
Be flexible, because if it doesn=92t work in one spot it may in another. T
oo bad the panel has to go in and out if you are wrong.
Electronics do go out of calibration from time to time, so a recalibration
of altimeter, airspeed and EFIS systems are necessary over the life of an E
FIS/NAV unit. It just costs money and time, but not extra weight.
Best Regards,
Bud Yerly
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s 10
________________________________
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matr
onics.com> on behalf of Remi Guerner <air.guerner@orange.fr>
Sent: Saturday, March 17, 2018 9:55:43 AM
Subject: Europa-List: GPS antenna cable length
This is a question for avionics gurus. After one full year of good service,
my G5 EFIS with its enabled internal GPS antenna started to display wrong
attitude information. After talking to the G3X team at Garmin, a software u
pdate fixed the issue, but after reviewing the recorded data of one of my f
lights, they came back to me and suggested I install an external antenna to
improve the GPS reception. So I purchased a GA26C antenna (picture attache
d). The antenna comes ready for use with an 8 ft cable and BNC connector. I
need only 2 ft to install the antenna on top of the instrument panel, ther
efore my questions: performance wise, is there an inconvenience to install
the antenna as it is and attach the loops of extra cable length together? I
s it worth cutting the extra length and install a new BNC connector? Would
that reduce possible losses and/or susceptibility to electromagnetic interf
erences ?
Remi Guerner
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