I agree entirely with Frans reply,
I was told during a conversation with the Trigg development engineers some
time ago not to use a perfectly circular ground plane at the calculated
diameter as it could possibly resonate and interfere with the signal in
some way , the reasoning as to why was well above my pay grade .
It is very easy to avoid this phenomena by making the ground plane slightly
irregular.
I use this as a reason for all my little add on bits being slightly
irregular. :<)
Tim
On 3 December 2012 16:53, Frans Veldman <frans@privatepilots.nl> wrote:
>
> On 12/03/2012 05:32 PM, skanderup wrote:
> allan_skanderup@hotmail.com>
> >
> > Hi,
> >
> > Now the talk is on antennas, I would like to ask the forum for your
> guidance on ground plane.
> >
> > I have purchased a nice antenna for my transponder and it requires a
> ground plane (which a GP aircraft does not provide automatically like a
> metal plane...)
>
> I hope you bought the TED antenna as it is the best available and also
> very affordable.
> A ground plane should be at least a quarter wave in radius. Quarter wave
> is the lenght of the antenna rod. A larger ground plane is ok, but has
> not much additional benefit.
>
> In my tri-gear I cut out the monowheel opening and use an aluminium
> plate to cover it. I mounted the antenna on the underside of the metal
> plate, and it works very well.
>
> As these radio waves are going through the glass fuselage, you could
> mount the antenna somewhere inside as well, and use any metal plate
> available. It is advisable to mount the antenna "upside down", that is,
> the metal rod sticking down. Beware of "shadows" like from the engine,
> so keep it as low as possible.
>
> Frans
>
>
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