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JohnCiolino(at)carolina.r
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 Posted: Thu Mar 07, 2013 3:13 am Post subject: ELT antenna inside tube and fabric fuselage |
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I am building a Legend Cub and intend to cover using the Poly-fiber process. That process uses a coat of aluminum pigmented dope (Poly-Spray) as UV protection.
I want to install the Comm and ELT antennas inside the fuselage, and ACK (ELT) says that can be done as long as the fabric is “of a non-conductive nature”. I asked ACK if the Poly-Spray would be non-conductive. They thought it would be OK but referred me to Poly-fiber.
Poly-fiber says the ELT antenna would be OK inside the fuselage but mount the Comm antenna outside. Several posters on the J-3cub.com site have reported good results using a dipole antenna inside the fuselage so the Poly-fiber advice does not seem right.
Has anyone had experience with antennas inside a Poly-fiber fuselage?
Thanks
John Ciolino
[quote][b]
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email(at)jaredyates.com
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| Posted: Thu Mar 07, 2013 4:54 am Post subject: ELT antenna inside tube and fabric fuselage |
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The polyspray might not be a concern, but what about the tubes? Are they steel?
On Mar 7, 2013, at 6:12, "John Ciolino" <JohnCiolino(at)carolina.rr.com (JohnCiolino(at)carolina.rr.com)> wrote:
[quote] <![endif]--> <![endif]-->
I am building a Legend Cub and intend to cover using the Poly-fiber process. That process uses a coat of aluminum pigmented dope (Poly-Spray) as UV protection.
I want to install the Comm and ELT antennas inside the fuselage, and ACK (ELT) says that can be done as long as the fabric is “of a non-conductive nature”. I asked ACK if the Poly-Spray would be non-conductive. They thought it would be OK but referred me to Poly-fiber.
Poly-fiber says the ELT antenna would be OK inside the fuselage but mount the Comm antenna outside. Several posters on the J-3cub.com site have reported good results using a dipole antenna inside the fuselage so the Poly-fiber advice does not seem right.
Has anyone had experience with antennas inside a Poly-fiber fuselage?
Thanks
John Ciolino
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st">http://www.matronics.com/Navigator?AeroElectric-List
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JohnCiolino(at)carolina.r
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| Posted: Thu Mar 07, 2013 5:35 am Post subject: ELT antenna inside tube and fabric fuselage |
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They are, but according to posters on the J-sCub.com site Comm radio reception and transmit is very good with a dipole antenna from Advance Aircraft Electronics mounted inside. No one has addressed the ELT antenna but as I mentioned the ACK folks say installation inside of a (steel) tube and fabric fuselage will meet their criteria if the fabric is non-conductive.
I am just not sure if the Poly-Spray coating makes the fabric conductive; apparently the steel tubes are not a factor. The ELT antenna probably has a better chance of survival inside the fuselage in the event of a crash.
John Ciolino
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Jared Yates
Sent: Thursday, March 07, 2013 7:54 AM
To: aeroelectric-list(at)matronics.com
Subject: Re: ELT antenna inside tube and fabric fuselage
The polyspray might not be a concern, but what about the tubes? Are they steel?
On Mar 7, 2013, at 6:12, "John Ciolino" <JohnCiolino(at)carolina.rr.com (JohnCiolino(at)carolina.rr.com)> wrote:
| Quote: |
I am building a Legend Cub and intend to cover using the Poly-fiber process. That process uses a coat of aluminum pigmented dope (Poly-Spray) as UV protection.
I want to install the Comm and ELT antennas inside the fuselage, and ACK (ELT) says that can be done as long as the fabric is “of a non-conductive nature”. I asked ACK if the Poly-Spray would be non-conductive. They thought it would be OK but referred me to Poly-fiber.
Poly-fiber says the ELT antenna would be OK inside the fuselage but mount the Comm antenna outside. Several posters on the J-3cub.com site have reported good results using a dipole antenna inside the fuselage so the Poly-fiber advice does not seem right.
Has anyone had experience with antennas inside a Poly-fiber fuselage?
Thanks
John Ciolino
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[quote][b]
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billp(at)wwpc.com
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| Posted: Thu Mar 07, 2013 7:22 am Post subject: ELT antenna inside tube and fabric fuselage |
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I'd mount all the antenna's outside. If there's enough aluminum in the dope to protect the fabric from UV, it's going to be pretty reflective of the RF from the radios. To much reflected power back into the antenna can damage transmitters. Having your ELT inside, at the very least, is going to reduce the range and make you harder to find.
Just my opinion from being an A&P/IA who's installed a lot of radios and an Extra Class Ham as well as Chief Engineer at a few FM broadcast stations.
Bill
On 3/7/13 3:12 AM, John Ciolino wrote:
[quote] <![endif]--> <![endif]-->
I am building a Legend Cub and intend to cover using the Poly-fiber process. That process uses a coat of aluminum pigmented dope (Poly-Spray) as UV protection.
I want to install the Comm and ELT antennas inside the fuselage, and ACK (ELT) says that can be done as long as the fabric is “of a non-conductive nature”. I asked ACK if the Poly-Spray would be non-conductive. They thought it would be OK but referred me to Poly-fiber.
Poly-fiber says the ELT antenna would be OK inside the fuselage but mount the Comm antenna outside. Several posters on the J-3cub.com site have reported good results using a dipole antenna inside the fuselage so the Poly-fiber advice does not seem right.
Has anyone had experience with antennas inside a Poly-fiber fuselage?
Thanks
John Ciolino
[b]
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james(at)etravel.org
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| Posted: Thu Mar 07, 2013 1:16 pm Post subject: ELT antenna inside tube and fabric fuselage |
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Hi John,
Here's a note from some time ago about some tests when I covered my plane with PolyFiber. You can find the full thread online, it was from about June 6 201. Bottom line: PolySpray didn't seem to make any difference...
HTH.
James
[b] | Quote: | [b] Gents,
I had been wondering, for some time, what to do about the PolyFiber
PolySpray coats. PolySpray is a metal-loaded paint that is used to
protect PolyFiber fabric from UV damage.
I'd wanted to put all the aerials inside my fuselage, but was
concerned that the PolySpray would attenuate radio signals to/from
COM, NAV, GPS (especially) and XPNDR. PolyFiber's own advice was to
put the aerials outside the fuselage, and to definitely use the
PolySpray coating, to ensure longevity of fabric (apparently the
PolySpray increases the fabric's life 4-fold!).
To cut a long story short, I decided to chance it -- with PolySpray
and internal aerials -- and see what happened, figuring that I could
move the aerials outside the fuselage if necessary.
Today, I did tests to see if the aerials function as I would wish, and
they did. The PolySpray coats appear to have made no difference to
the signals -- even the presumably very small GPS signal. I don't
have anything in the way of scientific instruments, just the signal
strength shown on the GPS and hand-held radio, but using the
fuselage-mounted aerials makes no discernible difference to the signal
strength compared to the equipment's own aerials. I've yet to test
the NAV / XPNDR aerials, but I assume the same will hold true for
those too.
FWIW!
James |
[/b][/b]
On 7 March 2013 11:12, John Ciolino <JohnCiolino(at)carolina.rr.com (JohnCiolino(at)carolina.rr.com)> wrote:
[quote]
I am building a Legend Cub and intend to cover using the Poly-fiber process. That process uses a coat of aluminum pigmented dope (Poly-Spray) as UV protection.
I want to install the Comm and ELT antennas inside the fuselage, and ACK (ELT) says that can be done as long as the fabric is “of a non-conductive nature”. I asked ACK if the Poly-Spray would be non-conductive. They thought it would be OK but referred me to Poly-fiber.
Poly-fiber says the ELT antenna would be OK inside the fuselage but mount the Comm antenna outside. Several posters on the J-3cub.com site have reported good results using a dipole antenna inside the fuselage so the Poly-fiber advice does not seem right.
Has anyone had experience with antennas inside a Poly-fiber fuselage?
Thanks
John Ciolino
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ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
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[b]
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james(at)etravel.org
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| Posted: Thu Mar 07, 2013 1:20 pm Post subject: ELT antenna inside tube and fabric fuselage |
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That would be terrific! It's a question that's asked quite a lot, and consistent repeatable tests would be terrific.
The guys at PolyFiber have always seemed very decent when I've met them and I wouldn't be surprised if they would be willing to help by supplying product or a suitable test frame.
James
On 7 March 2013 19:28, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 11:36 AM 3/7/2013, you wrote:
| Quote: | --> AeroElectric-List message posted by: Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)>
I have polyfiber leftovers to cover a box like that, and could use the opportunity as a covering demo/training for someone else.
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Great. I'm mulling over the geometry of a
polyfiber 'test cell' that would facilitate
relative attenuation measurements on a range
of antennas. Structure for the cell should
be RF transparent.
I'm thinking of a cylindrical tube on the
order of 6" diameter and 48" long covered
with exemplar polyfiber finished fabric.
[img]cid:.0[/img]
The tube would have a single split-cut over
half the length to a mast clearance hole in
the middle. This would allow it to be
slipped over dipole antennas covering our
range of interest. I'm thinking of tests at
130, 330, and 1000 Mhz which can be generated
and measured with equipment I have.
I wonder if a cardboard tube of the smallest practice
thickness could be used as a former. I considered
plastic DWV pipe . . . but these materials have some
degree of RF opacity. I guess we could have two
such tubes, one that's covered and one that is
not covered. That would wash out effects of the
plastic in the sandwich layers. Your thoughts
and the thoughts of others are welcome.
I'm negotiating a business arrangement
with a OBAM aircraft magazine to do a regular
flow of articles. This experiment might provide
the 'meat' for a first article .
Bob . . .
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kuffel(at)cyberport.net
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| Posted: Thu Mar 07, 2013 3:42 pm Post subject: ELT antenna inside tube and fabric fuselage |
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Bill Putney says:
<< I'd mount all the antenna's outside. .. To much reflected power back into the antenna can damage transmitters. Having your ELT inside, at the very least, is going to reduce the range and make you harder to find. >>
Bill is right, outside is best. Except for the ELT. My direct experience is having the ELT antenna outside leads to it often being removed during the crash which really reduces your range. Even with metal aircraft I recommend it be mounted inside but "visible" through the canopy/windows, etc. For example, on a friend's Zenith 701 we put the ELT in the middle of the instrument panel cover just behind the windshield. While such a location is far from ideal in a perfect propagation sense, data says if the crash is survivable then the internal antenna has enough performance for satellite pickup.
Don't have data for putting the antenna inside a tube framework. But basic radio theory says if there is enough leakage for the 121.5MHz signal to be heard then there is certainly enough leakage for the 406MHz signal. Try it and see. Limit any transmitter test to less than 30 seconds sometime between zero and five minutes past the hour.
Must disagree with the notion a proper antenna, even detuned by surroundings, can ever reflect enough power to damage a modern ELT transmitter. Am not aware of any ELT which can't tolerate 100% power reflection. This is what happens when an antenna is disconnected and the ELT is accidentally turned on.
Tom Kuffel
Since Bill noted his qualifications here are some of mine only partly tongue in cheek: CFI, search & rescue pilot (200+), Amateur Extra, former FCC First Class Phone, only Engineer not Chief Engineer at my FM station but it was over 50 years ago.
[quote][b]
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glastar(at)gmx.net
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| Posted: Fri Mar 08, 2013 2:18 am Post subject: ELT antenna inside tube and fabric fuselage |
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We had last year a forced landing here in Europe, because the rudder got detached after the start, flaring was difficult due to interference, that is how the
plane came to rest.
The antenna was broken off, but the ELT still worked, 15 minutes later the rescue helicopter arrived and the national organisation also called shortly after this as they did receive the alarm.
I would say a plus for the 406 System!
Werner
On 08.03.2013 00:42, The Kuffels wrote:
| Quote: | Bill Putney says:
<< I'd mount all the antenna's outside. .. To much reflected power back into the antenna can damage transmitters. Having your ELT inside, at the very least, is going to reduce the range and make you harder to find. >>
Bill is right, outside is best. Except for the ELT. My direct experience is having the ELT antenna outside leads to it often being removed during the crash which really reduces your range. Even with metal aircraft I recommend it be mounted inside but "visible" through the canopy/windows, etc. For example, on a friend's Zenith 701 we put the ELT in the middle of the instrument panel cover just behind the windshield. While such a location is far from ideal in a perfect propagation sense, data says if the crash is survivable then the internal antenna has enough performance for satellite pickup.
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kuffel(at)cyberport.net
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| Posted: Fri Mar 08, 2013 10:36 am Post subject: ELT antenna inside tube and fabric fuselage |
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Werner Schneider,
<< forced landing here in Europe ... The antenna was broken off, but the ELT still worked >>
Would have to examine the wreckage to be sure but it appears this relatively mild crash could be a case of the antenna being only partially broken off. The remaining stub would be an excellent 406MHz radiator. If the antenna was totally removed from the feed cable then it is hard to see the physics which would allow satellite reception. Perhaps if part of the cable shield was torn off, exposing the inner conductor, then you would have a useable antenna. The point is we can have absolutely miserable antenna placement and still have adequate ELT performance. Hence the statement we are better to have the ELT antenna inside, intact and working poorly and outside, missing and not working at all.
This aircraft appears to be wood construction. If so, the inside of the tail cone would be an excellent location.
Tom Kuffel
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