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MJKTuck(at)cs.com
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 Posted: Mon Jan 20, 2020 4:13 pm Post subject: Dipole com antenna |
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I'm thinking of switching from an external monopole type com antenna
(long rod sticking out at an angle with copper tape in a radiating
pattern on the fuselage floor) to a Bob Archer SA-006 dipole antenna.
The dipole appears looks like a '3' and made from thin sheet aluminum.
This '3' shape is what you attach the coax shield too (ground). The core
of the coax attaches to a small insulated aluminum plate in the middle
of the 3 shape.
Does anyone know how it works (the theory) and does anyone have one in
their Europa? How is it?
Regards,
Martin Tuck
N152MT
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h&jeuropa
Joined: 07 Nov 2006
Posts: 645
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| Posted: Tue Jan 21, 2020 8:23 am Post subject: Re: Dipole com antenna |
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Martin,
This is a simple dipole antenna with the radiating elements folded back to make it more compact. It is a very basic design and should work well. Be aware that it needs to be mounted on the side of the fuselage, not the floor or top and oriented so the coax is parallel to the longitudinal axis.
I've used similar antennas for ham radio work for many years.
Here is a link with more information:
https://sportcraftantennas.wordpress.com/2010/09/16/antennas-for-no-metal-airplane/
Jim Butcher
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MJKTuck(at)cs.com
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| Posted: Tue Jan 21, 2020 6:22 pm Post subject: Dipole com antenna |
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Hi Jim, thanks.
I now have a Dynon radio under the floor of the baggage bay so the coax
will route up the back of the baggage bay to about half way, then run
longitudinally mid-fuselage for about 18 inches at which point it will
mount to the SA-006 antenna plate. So, yes, the antenna will be mounted
vertically. I guess a portion of the coax will not be parallel to the
longitudinal axis due to the radio location. I figured it was more
important to have a short coax cable between the box and antenna.
I would still like to know the theory on how it works though, "simple
dipole antenna with the radiating elements folded back" doesn't help me
visualize what is going on.
Regards,
Martin
On 1/21/2020 10:23 AM, h&jeuropa wrote:
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h&jeuropa
Joined: 07 Nov 2006
Posts: 645
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| Posted: Thu Jan 23, 2020 8:46 am Post subject: Re: Dipole com antenna |
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Martin,
The Wikepedia article is a pretty good explanation,
https://en.wikipedia.org/wiki/Dipole_antenna
Because the ends are folded on the SA-006, the impedance of the antenna needs to matched to the feedline and the com output. Archer uses a gamma match for this.
Your planned installation sounds fine.
A dipole in the rear fin per the build manual also works very well but access on a completed airframe is somewhat difficult.
Jim
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MJKTuck(at)cs.com
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| Posted: Thu Jan 23, 2020 7:04 pm Post subject: Dipole com antenna |
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Thanks Jim,
I think later Europas had premoulded (hollow) fins. Mine has the
original foam core fin. However it sounds like the fuselage is fine also.
How it all works - well, it is all magic. 
Regards,
Martin
On 1/23/2020 10:46 AM, h&jeuropa wrote:
| Quote: |
Martin,
The Wikepedia article is a pretty good explanation,
https://en.wikipedia.org/wiki/Dipole_antenna
Because the ends are folded on the SA-006, the impedance of the antenna needs to matched to the feedline and the com output. Archer uses a gamma match for this.
Your planned installation sounds fine.
A dipole in the rear fin per the build manual also works very well but access on a completed airframe is somewhat difficult.
Jim
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494417#494417
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