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1. 10:01 AM - Re: Ground plane question... (Jeffrey Williams)
2. 12:42 PM - Re: Ground plane question... (Rowland Carson)
Message 1
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| Subject: | Re: Ground plane question... |
Thanks a lot, Bud, as well as Alan and David. I was hoping not to do
anything poking out into the wind. I appreciate the input!
Regards,
Jeff Williams
> On Aug 17, 2019, at 4:10 PM, Bud Yerly <budyerly@msn.com> wrote:
>
> Jeff,
>
> The ground plane depends on the transponder antenna.
> If building one yourself from braid wire like the com is done, yes one
is needed. If using an external antenna, yes of course. However:
>
> If using a Bob Archer Model 5 or Advanced Aircraft Electronics (AAE),
a ground plane is unneeded. I use the AAE exclusively because it is
quick to install, and works perfectly with any ADS-B / Mode S and
require no ground plane. I mount the transponder abeam the aft
inspection panel. I put a bit of a convex curve on the balsa support
supplied and a bit of Redux and tack with superglue until the Redux
cures. Been holding fine on all my aircraft since 2000 so it must work.
>
> The Bob Archer Model 5 is also quite good. It is larger and a bit
cumbersome.
>
> Place the com in the vertical tail works really well. Again I use the
AAE brand as it is bulletproof, easy to install and has little
thickness. They work with a BNC connectors either radial or tangential.
>
> AAE Nav antennas I put across the curve just behind baggage bulkhead.
Works fine, no VOR/ILS reception problems.
>
> GPS antennas work well in the Europa panel. I have two in mine
mounted below the top using a metal HAT Section Reduxed and or glassed
to the top.
>
> Garmin and Stratus supply a huge exterior mounted GPS that weighs
about 2 pounds. I use them, because I have to, but don=99t like
the weight. Both these suppliers have sufficient metal in the base for
ground plane and require no extra ground plane but do take up panel roof
top space. Plan well.
>
> I do sometimes use an aluminum ground plane for the ELT antenna, but
normally convince the owner to substitute the external ground plane
antenna for a composite installation antenna . The AAE com antenna is
fine for 121.5 and works with 406 but don=99t ask me how it works,
Artex says it is OK. Check with your specific ELT manufactuerer. The
small whip antenna ELT manufacturers supply, works with a six spoke
aluminum X on the base built inside the aircraft. Just Google it and
many of the manufacturers show how. A real pain to put in, so you see
why I go to the manufacturer and ask for a composite equivalent antenna.
Personally for ELTs I prefer the EBC type as there is no wiring.
Mount to the baggage bay side and press on with the build. The time
saved is worth the wiring and antenna mounting.
>
> I never put an antenna external to the clean skin of the Europa.
Therefore, no aluminum foil ground plane is necessary.
>
> Best Regards,
> Bud Yerly
>
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
Windows 10
>
> From: owner-europa-list-server@matronics.com
<mailto:owner-europa-list-server@matronics.com>
<owner-europa-list-server@matronics.com
<mailto:owner-europa-list-server@matronics.com>> on behalf of Jeffrey
Williams <jeffwill55@sbcglobal.net <mailto:jeffwill55@sbcglobal.net>>
> Sent: Friday, August 16, 2019 11:14:51 PM
> To: Europa-List Digest Server <europa-list@matronics.com
<mailto:europa-list@matronics.com>>
> Subject: Europa-List: Ground plane question...
>
<jeffwill55@sbcglobal.net>
>
> Maybe this one is for Bud Yerly, but anyone can chime in.
>
> I am installing instruments in my Europa XS and was told all
transponders need a ground plane. My research indicates a 12 inch circle
of thin copper or aluminum will do, but that the ground plane and the
antenna should be outside the aircraft so things like the engine and
other metal stuff doesn=99t interfere with the signal. I have a
Mode C and a Mode S to deal withand a GPS and Comm antenna too,
but those don=99t seem to need a ground plane. I am being informed
that these antennas need to be at least 40 inches apart as well. Also, I
have been told that putting the antenna itselfoutside the aircraft and
the ground plane inside is a bad idea that screws up the signal.
>
> Is any of this correct? What did you guys do?
>
> Regards,
>
> Jeff Williams
>
>
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Message 2
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| Subject: | Re: Ground plane question... |
On 2019-08-17, at 04:14, Jeffrey Williams <jeffwill55@sbcglobal.net> wrote:
> I am installing instruments in my Europa XS and was told all transponders need
a ground plane. My research indicates a 12 inch circle of thin copper or aluminum
will do, but that the ground plane and the antenna should be outside the
aircraft so things like the engine and other metal stuff doesnt interfere with
the signal. I have a Mode C and a Mode S to deal withand a GPS and Comm antenna
too, but those dont seem to need a ground plane. I am being informed that
these antennas need to be at least 40 inches apart as well. Also, I have been
told that putting the antenna itselfoutside the aircraft and the ground plane
inside is a bad idea that screws up the signal.
Jeff - my Trig manual says:
When a conventional aircraft monopole antenna is used it relies on a ground plane
for correct behaviour. For ideal performance the ground plane should be very
large compared to the wavelength of the transmission, which is 275mm. In a metal
skinned aircraft this is usually easy to accomplish, but is more difficult
in a composite or fabric skinned aircraft. In these cases a metallic ground
plane should be fabricated and fitted under the antenna.
As the ground plane is made smaller, the actual dimensions of the ground plane
become more critical, and small multiples of the wavelength should be avoided,
as should circles. Rectangles or squares are much less likely to create a critical
dimension that resonates with the transmissions. The smallest practical
ground plane is a square around 120mm per side; as the size increases the performance
may actually get worse, but will be better by the time the ground plane
is 700mm on each side. Anything much larger than that size is unlikely to show
significant further improvement.
The thickness of the material used to construct the ground plane is not critical,
providing it is sufficiently conductive. A variety of proprietary mesh and
grid solutions are available. Heavyweight cooking foil meets the technical requirements,
but obviously needs to be properly supported.
You can see what I did at:
http://www.rowlandcarson.org.uk/aviation/europa_435/transponder_installation.php
I made the minimum-size ground plane (120mm x 120mm) from 0.4mm copper sheet.
Caveat emptor - this has not yet been used in anger as the whole thing hasnt flown
yet!
in friendship
Rowland
| Rowland Carson ... that's Rowland with a 'w' ...
| <rowlandcarson@gmail.com> http://www.rowlandcarson.org.uk
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