Flat external FLARM antenna?

On Thursday, May 10, 2018 at 12:46:15 PM UTC-4, wrote:
On Thursday, May 10, 2018 at 11:08:48 AM UTC-4, Matt Herron Jr. wrote:
On Thursday, May 10, 2018 at 7:38:17 AM UTC-7, wrote:
On Thursday, May 10, 2018 at 10:07:15 AM UTC-4, Matt Herron Jr. wrote:
Flarm antennas are a real pain for ships with carbon hulls. Coverage is always poor, especially below. Is there a way to make a perfectly flat and thin antenna that could be taped to the outside of the hull and fed through a small (1/8"?) hole? I am thinking 2 thin wire strands, or foil strips, fed through from the inside, then taped in place with wing tape. I would put one on either side of the nose for good coverage. The wires could even be longer (some wavelength ratio) for better gain. The tiny hole could easily be filled later if the install was reversed.

Any RF engineers out there care to take a shot at this?

The power radiation pattern would not be favorable.
UH

Why is that?

Because the antenna would be too close, and parallel, to the conductive fuselage. A "whip" that is perpendicular to the fuselage (and 1/4 wavelength long - that's about 6 inches) would be much better, but of course add more drag, and be vulnerable to being damaged by tall grass etc. An antenna in an enclosed, streamlined bubble of a compromise depth and made of a non-conductive material (e.g., fiberglass) is probably the best solution.

- oops, (a bit over) 6 inches is half wavelength. 3 inches for quarter wavelength (which requires a ground plane). 300/MHz=wavelength in meters

On Thursday, May 10, 2018 at 2:01:16 PM UTC-7, wrote:
On Thursday, May 10, 2018 at 12:46:15 PM UTC-4, wrote:
On Thursday, May 10, 2018 at 11:08:48 AM UTC-4, Matt Herron Jr. wrote:
On Thursday, May 10, 2018 at 7:38:17 AM UTC-7, wrote:
On Thursday, May 10, 2018 at 10:07:15 AM UTC-4, Matt Herron Jr. wrote:
Flarm antennas are a real pain for ships with carbon hulls. Coverage is always poor, especially below. Is there a way to make a perfectly flat and thin antenna that could be taped to the outside of the hull and fed through a small (1/8"?) hole? I am thinking 2 thin wire strands, or foil strips, fed through from the inside, then taped in place with wing tape. I would put one on either side of the nose for good coverage. The wires could even be longer (some wavelength ratio) for better gain. The tiny hole could easily be filled later if the install was reversed.

Any RF engineers out there care to take a shot at this?

The power radiation pattern would not be favorable.
UH

Why is that?

Because the antenna would be too close, and parallel, to the conductive fuselage. A "whip" that is perpendicular to the fuselage (and 1/4 wavelength long - that's about 6 inches) would be much better, but of course add more drag, and be vulnerable to being damaged by tall grass etc. An antenna in an enclosed, streamlined bubble of a compromise depth and made of a non-conductive material (e.g., fiberglass) is probably the best solution.

- oops, (a bit over) 6 inches is half wavelength. 3 inches for quarter wavelength (which requires a ground plane). 300/MHz=wavelength in meters

Some available PowerFlarm antennas:
http://www.craggyaero.com/cables_&_antennas.htm

Richard
www.craggyaero.com

On Thursday, May 10, 2018 at 7:07:15 AM UTC-7, Matt Herron Jr. wrote:
Flarm antennas are a real pain for ships with carbon hulls. Coverage is always poor, especially below. Is there a way to make a perfectly flat and thin antenna that could be taped to the outside of the hull and fed through a small (1/8"?) hole? I am thinking 2 thin wire strands, or foil strips, fed through from the inside, then taped in place with wing tape. I would put one on either side of the nose for good coverage. The wires could even be longer (some wavelength ratio) for better gain. The tiny hole could easily be filled later if the install was reversed.

Any RF engineers out there care to take a shot at this?

Matt,
Not an RF Engineer but I am a self appointed internet expert and I think you and I have the same type of ship. Richard at Craggy sold me a whip (I have also heard this referred to as a duck) antenna to mount on the glare shield. Not sure how it would do directly beneath me (Would probably be in a turn if that were the case) but I get max range for transmission and reception. PM if you need a pic or call Richard.
Kirk

I have a PowerFlarm portable mounted on top of the glare shield of my
Stemme.Â* Also on the glare shield, in vertical orientation, are the
Flarm A & B antennae and the ADS-B antenna.Â* The Stemme is of all carbon
construction (except for a few parts).Â* One day I was flying a couple
thousand feet directly above another local pilot in a Discus 2, also of
carbon construction.Â* Though I could see him visually, neither of us
could see the other on Flarm as my antennae were above the carbon hull
of my ship and his ship was directly below.Â* I rolled up into a steep
bank and we each "saw" the other on the PF displays.

I good way to have all around coverage would be to place an external
antenna on the belly of the aircraft, but my PF unit only transmits on
the "A" antenna.Â* The "B" antenna is receive only.Â* I could get better
coverage below if I moved the antennae to the canopy frame but still
nothing directly below that was close enough to be a threat (and I'd
have a mess of cables to contend with).

On 5/10/2018 9:44 AM, K m wrote:
On Thursday, May 10, 2018 at 7:07:15 AM UTC-7, Matt Herron Jr. wrote:
Flarm antennas are a real pain for ships with carbon hulls. Coverage is always poor, especially below. Is there a way to make a perfectly flat and thin antenna that could be taped to the outside of the hull and fed through a small (1/8"?) hole? I am thinking 2 thin wire strands, or foil strips, fed through from the inside, then taped in place with wing tape. I would put one on either side of the nose for good coverage. The wires could even be longer (some wavelength ratio) for better gain. The tiny hole could easily be filled later if the install was reversed.

Any RF engineers out there care to take a shot at this?
Matt,
Not an RF Engineer but I am a self appointed internet expert and I think you and I have the same type of ship. Richard at Craggy sold me a whip (I have also heard this referred to as a duck) antenna to mount on the glare shield. Not sure how it would do directly beneath me (Would probably be in a turn if that were the case) but I get max range for transmission and reception. PM if you need a pic or call Richard.
Kirk

--
Dan, 5J

So are you talking about Flarm or PowerFlarm?? They are different you know.


On 05/10/2018 08:07 AM, Matt Herron Jr. wrote:
Flarm antennas are a real pain for ships with carbon hulls. Coverage is always poor, especially below. Is there a way to make a perfectly flat and thin antenna that could be taped to the outside of the hull and fed through a small (1/8"?) hole? I am thinking 2 thin wire strands, or foil strips, fed through from the inside, then taped in place with wing tape. I would put one on either side of the nose for good coverage. The wires could even be longer (some wavelength ratio) for better gain. The tiny hole could easily be filled later if the install was reversed.

Any RF engineers out there care to take a shot at this?

On Thursday, May 10, 2018 at 4:22:43 PM UTC-7, kinsell wrote:
So are you talking about Flarm or PowerFlarm?? They are different you know.


On 05/10/2018 08:07 AM, Matt Herron Jr. wrote:
Flarm antennas are a real pain for ships with carbon hulls. Coverage is always poor, especially below. Is there a way to make a perfectly flat and thin antenna that could be taped to the outside of the hull and fed through a small (1/8"?) hole? I am thinking 2 thin wire strands, or foil strips, fed through from the inside, then taped in place with wing tape. I would put one on either side of the nose for good coverage. The wires could even be longer (some wavelength ratio) for better gain. The tiny hole could easily be filled later if the install was reversed.

Any RF engineers out there care to take a shot at this?


power flarm

On 05/10/2018 05:54 PM, Matt Herron Jr. wrote:
On Thursday, May 10, 2018 at 4:22:43 PM UTC-7, kinsell wrote:
So are you talking about Flarm or PowerFlarm?? They are different you know.


On 05/10/2018 08:07 AM, Matt Herron Jr. wrote:
Flarm antennas are a real pain for ships with carbon hulls. Coverage is always poor, especially below. Is there a way to make a perfectly flat and thin antenna that could be taped to the outside of the hull and fed through a small (1/8"?) hole? I am thinking 2 thin wire strands, or foil strips, fed through from the inside, then taped in place with wing tape. I would put one on either side of the nose for good coverage. The wires could even be longer (some wavelength ratio) for better gain. The tiny hole could easily be filled later if the install was reversed.

Any RF engineers out there care to take a shot at this?


power flarm


Ah, that's what I guessed. But I shouldn't have to guess. If you mean
Flarm, say "Flarm", and if you mean PowerFlarm, say "PowerFlarm". If
you say "Classic Flarm", hopefully people will explain to you there's no
such thing.

See the recent thread with people who are shocked that Flarm isn't
approved for use in the US or Canada.

Two options come to mind.
1) Put the A antenna as high as reasonable around the glare shield. Away from other conductors that might mess with the pattern. I run with a piece of 1/16 lexan to put the antenna vertically above the glare shield. Use the Flarm web site tool to see what coverage you have. If there is a coverage hole behind and below, you could put a B antenna out the bottom. If it doesn't transmitt, it won't help others see you, but it should help you see others.

2) It seems like something in the tail leading edge should work well if you could figure out how to put the Flarm brick back there so the antenna cable was not excessive. This seems more trouble that it's worth unless the around the glare shield radiating out the canopy plan doesn't work.

On Thursday, May 10, 2018 at 3:07:15 PM UTC+1, Matt Herron Jr. wrote:
Flarm antennas are a real pain for ships with carbon hulls. Coverage is always poor, especially below. Is there a way to make a perfectly flat and thin antenna that could be taped to the outside of the hull and fed through a small (1/8"?) hole? I am thinking 2 thin wire strands, or foil strips, fed through from the inside, then taped in place with wing tape. I would put one on either side of the nose for good coverage. The wires could even be longer (some wavelength ratio) for better gain. The tiny hole could easily be filled later if the install was reversed.

Any RF engineers out there care to take a shot at this?



It is possible to make a flat antenna with the same radiation pattern as a 1/4 wave dipole.

But, it needs exotic ( read expensive) rf material, and would not be flexible, so hard to fit on the outside of the fuselage. thickness would be about 6-7mm, and would be unaffected by carbon fibre underneath it

It would also be 200-300€