Flarm Range Analysis

Thanks! All of the antennae are mounted on top of the glare shield and
I was concerned about coverage below and behind.

On 6/5/2017 3:22 PM, Matt Herron Jr. wrote:
On Monday, June 5, 2017 at 2:17:09 PM UTC-7, Dan Marotta wrote:
As a relatively new user of Flarm, I'm asking opinions of the
results I'm getting. Mine is a Power Flarm portable mounted to the
glare shield of my Stemme and has both Flarm A and B antennae and an
ADS-B antenna. Here's a link to my analysis on a flight yesterday
with plenty of Flarm targets: Flarm
Range Analysis.



Comments appreciated.


--

Dan, 5J
looks very acceptable. better than a lot I have seen. range at your 6 is great.

--
Dan, 5J

Very good reception compared to most of what I've seen. I would love to see a photo or detailed description of your antenna layout, in particular the location, orientation, and separation of the FLARM A and B antennas. I assume the former is mounted on the portable box itself.

Chip Bearden

I'll try to remember to get a picture but here's a description:

The Flarm portable is mounted to the top center of the glare shield on
the Stemme. The B antenna is mounted through a grommet directly in
front of me (left side) and about 6 inches forward of the aft edge of
the glare shield. The A antenna is mounted in the same location on the
right side of the glare shield (right side) and the ADS-B antenna is
mounted about 6 inches in front of the A antenna. The GPS antenna is
mounted on top of the glare shield near the forward center. I cut the
coax cables to length and ran them along the under side of the glare
shield cover where they exit their own grommets a couple of inches away
from where the antennae are mounted allowing for a perpendicular run of
coax from the antenna before turning down under the glare shield.


On 6/7/2017 7:21 PM, wrote:
Very good reception compared to most of what I've seen. I would love to see a photo or detailed description of your antenna layout, in particular the location, orientation, and separation of the FLARM A and B antennas. I assume the former is mounted on the portable box itself.

Chip Bearden

--
Dan, 5J

Both A & B antennae will be blocked by the engine and one or two bodies.

I'd look into placing the B antenna behind the gear in the tailcone.

On two Scout towplanes, I taped the dipole to a structural cross piece with
a
bit of balsa in between and connected to the A port. The B port got the
straight up antenna.

The problem is that the B antenna is receive only. So if the other guy is in you blind spot, he won't see you even if you can see him. A RF opaque glider needs at least two transmit antennas to get a full situational picture.

And as Mark points out, the range tool is a 2D projection of 3D data. So the good range shown could be based on a cone pointing up or down. It's possible your range is near zero on or near the horizon.

Maybe the range tool should provide several charts for different azimuths. But ti would still not be quite right because some hits would be while the glider is banked. So now the range tool should analyze the track and estimate bank angle.

Gets complicated pretty fast :-)

5Z

On Thursday, June 8, 2017 at 2:00:04 PM UTC-7, George Haeh wrote:
Both A & B antennae will be blocked by the engine and one or two bodies.

I'd look into placing the B antenna behind the gear in the tailcone.

On two Scout towplanes, I taped the dipole to a structural cross piece with
a
bit of balsa in between and connected to the A port. The B port got the
straight up antenna.

Understood.

Along those lines, I recall in my AF jet, the transponder had an antenna
select switch - Top, Auto, Bottom. That would be nice for the Flarm.

On 6/8/2017 10:40 PM, wrote:
The problem is that the B antenna is receive only. So if the other guy is in you blind spot, he won't see you even if you can see him. A RF opaque glider needs at least two transmit antennas to get a full situational picture.

And as Mark points out, the range tool is a 2D projection of 3D data. So the good range shown could be based on a cone pointing up or down. It's possible your range is near zero on or near the horizon.

Maybe the range tool should provide several charts for different azimuths. But ti would still not be quite right because some hits would be while the glider is banked. So now the range tool should analyze the track and estimate bank angle.

Gets complicated pretty fast :-)

5Z

On Thursday, June 8, 2017 at 2:00:04 PM UTC-7, George Haeh wrote:
Both A & B antennae will be blocked by the engine and one or two bodies.

I'd look into placing the B antenna behind the gear in the tailcone.

On two Scout towplanes, I taped the dipole to a structural cross piece with
a
bit of balsa in between and connected to the A port. The B port got the
straight up antenna.

--
Dan, 5J

Here are those pictures you asked for:

https://www.dropbox.com/s/nd4z1itc0i...41.15.jpg?dl=0
https://www.dropbox.com/s/fxt1nog20c...23.34.jpg?dl=0
https://www.dropbox.com/s/banwv1ljv1...23.23.jpg?dl=0
https://www.dropbox.com/s/2bqq8ez1ag...22.30.jpg?dl=0

Hope that helps. I know it would help with my reception to place the B
antenna on the bottom of the aircraft, but that would be a pain in the
behind - hardware, cabling, convincing the IA to sign off the
installation, etc.

Dan

On 6/8/2017 8:42 AM, Dan Marotta wrote:
I'll try to remember to get a picture but here's a description:

The Flarm portable is mounted to the top center of the glare shield on
the Stemme. The B antenna is mounted through a grommet directly in
front of me (left side) and about 6 inches forward of the aft edge of
the glare shield. The A antenna is mounted in the same location on
the right side of the glare shield (right side) and the ADS-B antenna
is mounted about 6 inches in front of the A antenna. The GPS antenna
is mounted on top of the glare shield near the forward center. I cut
the coax cables to length and ran them along the under side of the
glare shield cover where they exit their own grommets a couple of
inches away from where the antennae are mounted allowing for a
perpendicular run of coax from the antenna before turning down under
the glare shield.


On 6/7/2017 7:21 PM, wrote:
Very good reception compared to most of what I've seen. I would love
to see a photo or detailed description of your antenna layout, in
particular the location, orientation, and separation of the FLARM A
and B antennas. I assume the former is mounted on the portable box
itself.

Chip Bearden


--
Dan, 5J

On Thursday, June 8, 2017 at 9:58:39 PM UTC-4, Dan Marotta wrote:
Here are those pictures you asked for:

https://www.dropbox.com/s/nd4z1itc0i...41.15.jpg?dl=0
https://www.dropbox.com/s/fxt1nog20c...23.34.jpg?dl=0
https://www.dropbox.com/s/banwv1ljv1...23.23.jpg?dl=0
https://www.dropbox.com/s/2bqq8ez1ag...22.30.jpg?dl=0

Hope that helps. I know it would help with my reception to place the B
antenna on the bottom of the aircraft, but that would be a pain in the
behind - hardware, cabling, convincing the IA to sign off the
installation, etc.

Dan

On 6/8/2017 8:42 AM, Dan Marotta wrote:
I'll try to remember to get a picture but here's a description:

The Flarm portable is mounted to the top center of the glare shield on
the Stemme. The B antenna is mounted through a grommet directly in
front of me (left side) and about 6 inches forward of the aft edge of
the glare shield. The A antenna is mounted in the same location on
the right side of the glare shield (right side) and the ADS-B antenna
is mounted about 6 inches in front of the A antenna. The GPS antenna
is mounted on top of the glare shield near the forward center. I cut
the coax cables to length and ran them along the under side of the
glare shield cover where they exit their own grommets a couple of
inches away from where the antennae are mounted allowing for a
perpendicular run of coax from the antenna before turning down under
the glare shield.


On 6/7/2017 7:21 PM,
Very good reception compared to most of what I've seen. I would love
to see a photo or detailed description of your antenna layout, in
particular the location, orientation, and separation of the FLARM A
and B antennas. I assume the former is mounted on the portable box
itself.

Chip Bearden


--
Dan, 5J

I would recommend to put the 2nd Flarm recieve antenna in a more diverse location - such as below the insturments and or below and behind the engine. This should provide more reception from people below you.
Chris

I'm pretty sure that the reason that Flarm does not provide 3D information revolves around the fact that the data available is very limited. You can get some sense for your antenna performance only by collapsing a data set into a single plane to get enough points to do some averaging. Even though collapsed into a plane, the data is still quite granular. Remember also that each data point is not a measure of own ship performance; it is the composite performance of own ship and target ship Powerflarm systems. So averaging results from multiple ships is fundamentally necessary to get meaningful information. There just isn't enough data.

On Tuesday, June 13, 2017 at 9:35:33 AM UTC-4, Steve Koerner wrote:
I'm pretty sure that the reason that Flarm does not provide 3D information revolves around the fact that the data available is very limited. You can get some sense for your antenna performance only by collapsing a data set into a single plane to get enough points to do some averaging. Even though collapsed into a plane, the data is still quite granular. Remember also that each data point is not a measure of own ship performance; it is the composite performance of own ship and target ship Powerflarm systems. So averaging results from multiple ships is fundamentally necessary to get meaningful information. There just isn't enough data.

That is why is makes sense to concatenate several flight recordings together. There seems to be a limit of ~4mb (~10hours) but I would suggest that flarm should allow you to put about 50-100 hours of flight data into one analysis to get the required information.
Plus collapsing into the top view plan is just as arbitrary as any other plane, they should provide the option to collapse into side view plane also.