Flat external FLARM antenna?

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 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

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?

The power radiation pattern would not be favorable.
UH

Why is that?

Take a look at http://b1.ifrm.com/2510/101/0/p10229...ionPattern.gif ..

Your wires, facing fore/aft, would radiate as a dipole. Good to the sides, no coverage in front or behind - arguably the most important place to have coverage.

You can see with a vertical antenna, you have good all-quadrant horizontal coverage, but are unprotected from a vertical attack (you still have coverage above and below for close transmitters via side lobes). It has good coverage for +/- 20 degrees from the horizon - which is where the vast majority of the threat exists.

On Thursday, May 10, 2018 at 8:17:35 AM UTC-7, Dan Daly wrote:
The power radiation pattern would not be favorable.
UH

Why is that?

Take a look at http://b1.ifrm.com/2510/101/0/p10229...ionPattern.gif .

Your wires, facing fore/aft, would radiate as a dipole. Good to the sides, no coverage in front or behind - arguably the most important place to have coverage.

You can see with a vertical antenna, you have good all-quadrant horizontal coverage, but are unprotected from a vertical attack (you still have coverage above and below for close transmitters via side lobes). It has good coverage for +/- 20 degrees from the horizon - which is where the vast majority of the threat exists.

Dan D., my intent was to orient the wires vertically on the outside of the ship. However, Dan M has reminded me that only one antenna transmits. Therefor I would only be seen from one side of the ship. That doesn't work.

Perhaps a vertical dipole above the glare shield for transmit, and a transversely mounted "tape" antenna on the belly. The transverse mount (along the axis of the wings), even though it is mostly horizontal would give good reception forward, below, and to the rear. the dipole would x-mit and receive forward, and to the sides, but not below or behind that well.

Matt

On Thursday, May 10, 2018 at 12:21:35 PM UTC-4, Matt Herron Jr. wrote:
On Thursday, May 10, 2018 at 8:17:35 AM UTC-7, Dan Daly wrote:
The power radiation pattern would not be favorable.
UH

Why is that?

Take a look at http://b1.ifrm.com/2510/101/0/p10229...ionPattern.gif .

Your wires, facing fore/aft, would radiate as a dipole. Good to the sides, no coverage in front or behind - arguably the most important place to have coverage.

You can see with a vertical antenna, you have good all-quadrant horizontal coverage, but are unprotected from a vertical attack (you still have coverage above and below for close transmitters via side lobes). It has good coverage for +/- 20 degrees from the horizon - which is where the vast majority of the threat exists.

Dan D., my intent was to orient the wires vertically on the outside of the ship. However, Dan M has reminded me that only one antenna transmits. Therefor I would only be seen from one side of the ship. That doesn't work.

Perhaps a vertical dipole above the glare shield for transmit, and a transversely mounted "tape" antenna on the belly. The transverse mount (along the axis of the wings), even though it is mostly horizontal would give good reception forward, below, and to the rear. the dipole would x-mit and receive forward, and to the sides, but not below or behind that well.

Matt

Matt, ok, I didn't understand the planned orientation. The belly FLARM B would receive, so in a high/low situation, at least one of you would get an alarm.

On Thursday, May 10, 2018 at 8:08:48 AM UTC-7, 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?

Laws of physics/Maxwells' equations, antenna design theory, radiation/gain patterns of patch antennas,.... there are lots of articles online about patch antenna design and performance if you want to drill there.

You can't just tape a wire near a conductive surface and think you have built an antenna. That is likely to create a non-antenna. You need a proper designed patch antenna..

Patch antennas attached to glider sides are going to have very limited forward/rear visibility (the directions that matter the most) and I expect you would need more than those two side antennas to provide coverage around the aircraft, and that is all non trivial to combine. We've got two FLARM receivers in PowerFLARM to do that, and in the USA only one of those also transmits, and only one ADS-B receiver, not close enough to what you would need for 360 coverage.

Patch antennas work great for entirely different things like looking in one basic direction, like "up" for GPS and Globalstar and Iridium, all with circular polarization, which importantly makes them horizontal rotation orientation independent (although patch antennas don't have to be circular polarized).

It's possible to get standard FLARM antennas to work in your ASW27 so just go that route.

Darryl (background in microwave electronics research).

On Thursday, May 10, 2018 at 9:44:28 AM UTC-7, Darryl Ramm wrote:
On Thursday, May 10, 2018 at 8:08:48 AM UTC-7, 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?

Laws of physics/Maxwells' equations, antenna design theory, radiation/gain patterns of patch antennas,.... there are lots of articles online about patch antenna design and performance if you want to drill there.

You can't just tape a wire near a conductive surface and think you have built an antenna. That is likely to create a non-antenna. You need a proper designed patch antenna..

Patch antennas attached to glider sides are going to have very limited forward/rear visibility (the directions that matter the most) and I expect you would need more than those two side antennas to provide coverage around the aircraft, and that is all non trivial to combine. We've got two FLARM receivers in PowerFLARM to do that, and in the USA only one of those also transmits, and only one ADS-B receiver, not close enough to what you would need for 360 coverage.

Patch antennas work great for entirely different things like looking in one basic direction, like "up" for GPS and Globalstar and Iridium, all with circular polarization, which importantly makes them horizontal rotation orientation independent (although patch antennas don't have to be circular polarized).

It's possible to get standard FLARM antennas to work in your ASW27 so just go that route.

Darryl (background in microwave electronics research).

How do I get coverage below the glider in this scenario?

On Thursday, May 10, 2018 at 9:49:33 AM UTC-7, Matt Herron Jr. wrote:
On Thursday, May 10, 2018 at 9:44:28 AM UTC-7, Darryl Ramm wrote:
On Thursday, May 10, 2018 at 8:08:48 AM UTC-7, 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?

Laws of physics/Maxwells' equations, antenna design theory, radiation/gain patterns of patch antennas,.... there are lots of articles online about patch antenna design and performance if you want to drill there.

You can't just tape a wire near a conductive surface and think you have built an antenna. That is likely to create a non-antenna. You need a proper designed patch antenna..

Patch antennas attached to glider sides are going to have very limited forward/rear visibility (the directions that matter the most) and I expect you would need more than those two side antennas to provide coverage around the aircraft, and that is all non trivial to combine. We've got two FLARM receivers in PowerFLARM to do that, and in the USA only one of those also transmits, and only one ADS-B receiver, not close enough to what you would need for 360 coverage.

Patch antennas work great for entirely different things like looking in one basic direction, like "up" for GPS and Globalstar and Iridium, all with circular polarization, which importantly makes them horizontal rotation orientation independent (although patch antennas don't have to be circular polarized).

It's possible to get standard FLARM antennas to work in your ASW27 so just go that route.

Darryl (background in microwave electronics research).

How do I get coverage below the glider in this scenario?

That is what the FLARM B antenna is to help you do. And lots of vendors can sell you different external FLARM antennas to mount on the glider fuselage.. I can sell you mine sitting useless in its box if you want, in as new condition. It can be a PITA to find a location to install it. Easier in your ASW27 than my ASH26E. And it may well be more or as much rear coverage as below coverage you want it to help with.

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.