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...stallation.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."