Bud
thanks
A funny thing... I have an antenna "connector" underneath the doorsill
(like many things I do, I don't have an answer as to why I did this except
that it seemed like a good idea at the time....). So anyway after my tank
rebuild I reconnect the com to the Artex ELT whip antenna (no ground plane)
and the ELT to the com antenna (AAE antenna). I had it like this for
about 2 weeks. Everyone could hear me fine and I could hear traffic
in Pahokee about 100m away.
Back to the question at hand.
I know that Artex will say that you have to use their antenna. That said I
am wondering if there is a solution more in tune with our aircraft. My
aircraft already has its airworthiness so no inspectors to offend* "install
the antenna within 20 degrees of vertical and near the fuselage centerline
or the inspector will die of a heart attack".*
Do you think that this would work?
https://www.kitplanes.com/elt-enlightenment/.
[image: image.png]
Construction details for the antenna (left). The element on the left is the
classic =9Cstraight out=9D layout while the element on the righ
t is how you can
build it missing random structures while still remaining a good antenna.
Both elements can be straight, both elements can be crooked, or it can be
as shown, one straight and one crooked. Do not under any circumstances ask
me what the pattern is going to look like for a crooked antenna element.
How well did we match the transmitter to the antenna? At 121.5 MHz the
match is about 2.5, and at 406 the match is a little better at 2.2. Either
one is more than acceptable (right).
*For those of you with plastic ships, a plain old half-wave (two
quarter-wave elements made of half-inch copper tape 21.2 inches long )
dipole will work well. Simple, cheap, and works perfectly. You can bend it
around, twist it to miss structural members or lay it out perfectly
straight. Just remember that maximum radiation is at right angles to the
antenna and practically none off the ends of the elements.*
*The question has often been asked of me, =9CShould the ELT antenna b
e
mounted horizontally or vertically?=9D The answer has always been the
same:
If you can tell me the orientation of the crumpled remains of the fuselage
in the middle of the dust cloud when you really need the ELT, I can tell
you the orientation. In my experience, a random guess is every bit as good
as anything else.*
It sounds like I could make a zigzag antenna as long as each leg is 21.2".
Perhaps the rear cabin bulkhead might be a good location.
Thanks Will
William Daniell
LONGPORT
+1 786 878 0246
On Sun, Jan 8, 2023 at 11:14 AM Bud Yerly <budyerly@msn.com> wrote:
> Will,
> I've installed the ELT antenna a number of ways.
>
> I've installed an AAE carbon fiber antenna with a splitter for a handheld
> antenna to also connect to for better backup com options. VHF only
>
> I've simply installed the whip antenna with a radial ground plane equal t
o
> the antenna length in the rear floor and a small support for the antenna
> tip to prevent it from making noise.
>
> I've installed a tail mounted dipole unit onto a tail post before
> finishing (no com antenna near it).
>
> Normally the Artex or now discontinued AmeriKing were mostly installed
> below the baggage bay for ease of service. It was simple to run a coax t
o
> the whip antenna supplied or an AAE carbon antenna. The new 406/121.5 du
al
> frequency whip antenna Artex uses is supposedly good for both frequencies
.
> For VHF 121.5 the ground plane for a quarter wave is 33-36 inches but som
e
> do a half 1/4 wave so about 8.5 inches diameter, but I find the signal we
ak
> using a handheld vhf on 121.5 using an 8 inch circle alone. Since the
> Artex 345 is a 15 inch whip antenna a simple 15 inch radius ground plane
of
> 4-8 radials works fine.
>
> I always had to laugh at myself when explaining to a customer that placin
g
> the ELT antenna and the com also in the mid fuselage was interesting. As
> the ELT only works when you crash so who cares about spacing the antennas
> except for reflection, then if separated by 36 inches, reflection is not
an
> issue. Heck in our composite aircraft I wonder if we could just use the
> gear leg as part of the dipole. Some smart guy needs to look into that.
>
> Just run a couple of tapes about 30 inches long out from the hat section
> in the drawing I've attached, and it works. Normally I tack the legs wit
h
> superglue then lay a thin bit of glass over the fragile copper tape. Som
e
> use a copper braid and some just run aluminum strips using aluminum tape
> but if using tape make sure you remove the glue at the contact points to
> assure a good ground. If near the side of the fuselage just run the spid
er
> web out one side. It still works but is a bit directional. I won't run
a
> radius up the fuselage wall vertically where it can reflect back at the
> antenna.
>
> We don't know what direction the fuselage will end up in a crash but
> install the antenna within 20 degrees of vertical and near the fuselage
> centerline or the inspector will die of a heart attack.
>
> Best Regards,
> Bud Yerly
>
> My ELT is an EBC 302 121.5 and 243.0 VHF/UHF Easy to install but the
> alkaline battery is expensive and can corrode destroying the unit.
> Replacement for a 406 model is prohibitively expensive.
>
>
> -----Original Message-----
> From: owner-europa-list-server@matronics.com <
> owner-europa-list-server@matronics.com> On Behalf Of rparigoris
> Sent: Saturday, January 07, 2023 2:38 PM
> To: europa-list@matronics.com
> Subject: Europa-List: Re: ELT position and antenna
>
>
> Hi Will
>
> Forgot to mention, on both of our ELTs, Mfg said if their antenna wasn't
> used, unit would not be officially blessed. Both said OK to extend antenn
a
> location with coax. Both suggested using a ground plane. That said won't
do
> you much good if upside down.
>
> Ron P.
>
>
> Read this topic online here:
>
>
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