Flat external FLARM antenna?

[Matt Herron Jr.]

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?

[[email protected]]

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

[Matt Herron Jr.]

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?

[Dan Daly[_2_]]

> > The power radiation pattern would not be favorable.
> > UH
>
> Why is that?

Take a look at http://b1.ifrm.com/2510/101/0/p1022927/RadiationPattern.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.

[K m]

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 Marotta]

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

[Matt Herron Jr.]

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/p1022927/RadiationPattern.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

[Dan Daly[_2_]]

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/p1022927/RadiationPattern.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.

[Darryl Ramm]

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).

[[email protected]]

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.

[Matt Herron Jr.]

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?

[Darryl Ramm]

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.

[Dan Marotta]

You could mount your Flarm antennae to the canopy frame, left and right,
for best all around coverage.Â* Mount them as high as possible using
L-shaped brackets made of bent plastic or formed fiberglass. The
brackets could be mounted to the canopy frame with glue, dual-lok
fastener, double sided tape, etc., or with a screw (I'd suggest brass
for the screw if you go that way).Â* The individual antennae could be
mounted to the L-brackets with Velcro, glue, double tape, etc.

Or, you could mount one antenna buried half way in the glare shield,
held in place with a quarter inch ID grommet.Â* Install another grommet
2-3 inches away through which to pass the cable.Â* Keep the cable
perpendicular to the antenna for a couple of inches before turning it
down to its grommet.Â* Mount an external antenna under the fuselage aft
of the landing gear doors and offset it 4-6 inches to one side.Â* Pick
the location by trial and error before drilling any holes.Â* With the
antenna mounted as described, it will not be at risk of damage loading
the glider into the trailer.Â* You could possibly also spare the antenna
being destroyed in a gear up landing by careful choice of location, but
it you land gear up you have more worries than a broken antenna...

Look around on the net; there are pictures of the things I've described.

On 5/10/2018 11:11 AM, Darryl Ramm wrote:
> 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.

--
Dan, 5J

[Darryl Ramm]

Lets be careful what antennas are being talked about. Most in-cockpit side by side antennas are FLARM A and 1090ES. I can't tell what is being discussed here, but not burying the antennas below the glareshield behind wires and instrument cases and carbon fuselage sides etc. always helps.

Since (in the USA) FLARM A is the only transmitting antenna the most important thing to do is get that antenna best positioned. FLARM B is the intended to be used to the rear and/or below to supplement the FLARM A antenna.

There is a very helpful FLARM antenna installation document (started by Dave Nadler) at https://flarm.com/wp-content/uploads/man/FTD-041-Application-Note-FLARM-Antenna-Installation.pdf.


On Thursday, May 10, 2018 at 10:44:51 AM UTC-7, Dan Marotta wrote:
> You could mount your Flarm antennae to the canopy frame, left and right,
> for best all around coverage.Â* Mount them as high as possible using
> L-shaped brackets made of bent plastic or formed fiberglass. The
> brackets could be mounted to the canopy frame with glue, dual-lok
> fastener, double sided tape, etc., or with a screw (I'd suggest brass
> for the screw if you go that way).Â* The individual antennae could be
> mounted to the L-brackets with Velcro, glue, double tape, etc.
>
> Or, you could mount one antenna buried half way in the glare shield,
> held in place with a quarter inch ID grommet.Â* Install another grommet
> 2-3 inches away through which to pass the cable.Â* Keep the cable
> perpendicular to the antenna for a couple of inches before turning it
> down to its grommet.Â* Mount an external antenna under the fuselage aft
> of the landing gear doors and offset it 4-6 inches to one side.Â* Pick
> the location by trial and error before drilling any holes.Â* With the
> antenna mounted as described, it will not be at risk of damage loading
> the glider into the trailer.Â* You could possibly also spare the antenna
> being destroyed in a gear up landing by careful choice of location, but
> it you land gear up you have more worries than a broken antenna...
>
> Look around on the net; there are pictures of the things I've described.
>
> On 5/10/2018 11:11 AM, Darryl Ramm wrote:
> > 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.
>
> --
> Dan, 5J

[Mike the Strike]

Any time you reduce an antenna's length to much below a half-wave, its efficiency drops dramatically. Years ago, for a glider radio experiment, I made a half-wave dipole antenna out of self-adhesive aluminum foil stuck onto the canopy out of direct vision. I wondered whether this approach might work with Flarm?

Mike

[[email protected]]

On Thursday, May 10, 2018 at 2:29:27 PM UTC-4, Darryl Ramm wrote:
> Lets be careful what antennas are being talked about. Most in-cockpit side by side antennas are FLARM A and 1090ES. I can't tell what is being discussed here, but not burying the antennas below the glareshield behind wires and instrument cases and carbon fuselage sides etc. always helps.
>
> Since (in the USA) FLARM A is the only transmitting antenna the most important thing to do is get that antenna best positioned. FLARM B is the intended to be used to the rear and/or below to supplement the FLARM A antenna.
>
> There is a very helpful FLARM antenna installation document (started by Dave Nadler) at https://flarm.com/wp-content/uploads/man/FTD-041-Application-Note-FLARM-Antenna-Installation.pdf.
>
>
> On Thursday, May 10, 2018 at 10:44:51 AM UTC-7, Dan Marotta wrote:
> > You could mount your Flarm antennae to the canopy frame, left and right,
> > for best all around coverage.Â* Mount them as high as possible using
> > L-shaped brackets made of bent plastic or formed fiberglass. The
> > brackets could be mounted to the canopy frame with glue, dual-lok
> > fastener, double sided tape, etc., or with a screw (I'd suggest brass
> > for the screw if you go that way).Â* The individual antennae could be
> > mounted to the L-brackets with Velcro, glue, double tape, etc.
> >
> > Or, you could mount one antenna buried half way in the glare shield,
> > held in place with a quarter inch ID grommet.Â* Install another grommet
> > 2-3 inches away through which to pass the cable.Â* Keep the cable
> > perpendicular to the antenna for a couple of inches before turning it
> > down to its grommet.Â* Mount an external antenna under the fuselage aft
> > of the landing gear doors and offset it 4-6 inches to one side.Â* Pick
> > the location by trial and error before drilling any holes.Â* With the
> > antenna mounted as described, it will not be at risk of damage loading
> > the glider into the trailer.Â* You could possibly also spare the antenna
> > being destroyed in a gear up landing by careful choice of location, but
> > it you land gear up you have more worries than a broken antenna...
> >
> > Look around on the net; there are pictures of the things I've described..
> >
> > On 5/10/2018 11:11 AM, Darryl Ramm wrote:
> > > 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.
> >
> > --
> > Dan, 5J

This bit from that PDF may come in handy:

"In carbon fiber gliders, the Port B antenna may be placed in or near the gear box to improve range below, if the gear doors are not made of carbon."

[[email protected]]

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

[Richard Pfiffner[_2_]]

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

[kinsell]

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?
>

[Matt Herron Jr.]

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

[[email protected]]

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.

[kinsell]

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.

[Chris Wedgwood[_2_]]

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€