Today's Message Index:
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1. 07:26 AM - Re: Lithium Battery and Alternator Failure (user9253)
2. 09:56 AM - Transponder antenna ground plane (Tom Barter)
3. 02:26 PM - Re: Transponder antenna ground plane (user9253)
4. 02:36 PM - Re: Transponder antenna ground plane (Charlie England)
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| Subject: | Re: Lithium Battery and Alternator Failure |
Below are the results of a poll taken on VansAirforce. https://vansairforce.net/community/poll.php?do=showresults&pollid=403
Alternator Failures in 250 hours of use:
Automotive conversion: 5.6 %
Plane Power: 13.5 %
B&C: Less than 1 %
Due to the small number of respondents, the results might not be statistically
significant.
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Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503541#503541
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| Subject: | Transponder antenna ground plane |
Greetings,
I'm preparing to install the ground plane for the transponder antenna on my
steel tube fabric covered plane. It would be more convenient to mount the
transponder antenna ground plane on the inside of the fuselage, on the
bottom behind the baggage compartment. This would require a 7/8" thick
spacer so the antenna would mount flush with the fabric. If I machined such
a spacer from solid aluminum and made sure of low resistance connections
between the spacer and the ground plane, would this adversely affect the
antenna performance?
Any advice appreciated.
Tom Barter
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| Subject: | Re: Transponder antenna ground plane |
Read this thread:
http://www.matronics.com/forums/viewtopic.php?t=16762861
I would mount the transponder antenna to a 5.3 inch diameter ground plane.
Make sure the outer braid of the coaxial cable is electrically connected to the
ground plane.
The antenna ground plane does not need to be electrically connected to the tubular
steel airframe.
Wood could be used between the ground plane and airframe steel tubes to support
the antenna where desired.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503543#503543
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| Subject: | Re: Transponder antenna ground plane |
On 10/16/2021 11:55 AM, Tom Barter wrote:
>
> Greetings,
>
> Im preparing to install the ground plane for the transponder antenna
> on my steel tube fabric covered plane. It would be more convenient to
> mount the transponder antenna ground plane on the inside of the
> fuselage, on the bottom behind the baggage compartment. This would
> require a 7/8 thick spacer so the antenna would mount flush with the
> fabric. If I machined such a spacer from solid aluminum and made sure
> of low resistance connections between the spacer and the ground plane,
> would this adversely affect the antenna performance?
>
> Any advice appreciated.
>
> Tom Barter
>
Have you considered just flipping the assy over, so the xpndr spike
points up? Fabric skin does little to attenuate RF, so if you can avoid
punching another hole, why not? There might be a little 'shadowing' of
the signal if you're too close to an aluminum baggage compartment, but I
doubt you'd ever know without taking the plane to an 'antenna range'
with a lot of expensive measuring hardware. I've heard of people putting
them inside cowlings, and the uAvionix tech recommended that I mount
their Echo UAT box, the WAAS GPS, and the antenna spike all on a plate
within the fiberglass wingtip of my RV6. Obviously, there's much more
shadowing by the wing rib than anything you'd see, and he told me that
they have numerous examples flying that way.
To answer your actual question, extra aluminum on the back side of the
ground plane should have no effect on the antenna's performance. Think
of it as a much fatter, stronger 'bulkhead', as you would see inside
aluminum skinned a/c near the xpndr antenna mount.
FWIW,
Charlie
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