PowerFlarm Range Issues

[Richard Pfiffner]

I have had many calls recently about range problems with Powerflarm.

Most think it is related to the antenna. Sometimes yes and sometimes no.

Antennas are very simple. If you have metal or carbon fiber between your antenna and the target you will not see the target.

Antennas mounted below the panel cover will probably have degraded or no range. Antennas partially sticking out of the instrument panel cover also will have degraded range. These antennas may partially work in a thermal with a high bank angle (no block between your antenna and the target).

If you have good antenna installations it is probably related to a damaged board in the PowerFlarm.

See this link for antenna installation

https://www.craggyaero.com/PowerFlarm/Application-Note-FLARM-Antenna-Installation-1.pdf


See this link for different antenna solutions.

https://www.craggyaero.com/cables_&_antennas.htm

See this link for PowerFlarm Testing and and repair.

https://www.craggyaero.com/powerflarm_fsp.htm

Richard,
www.craggyaero.com

[Dan Daly]

If you have an OGN receiver within range, you can load https://glidertracker.org/ , then center it on your receiver. Click on your glider symbol. A box comes up with information, one of which is the received signal strength. If very close, it can be 40-50 dB. If you are very close and it is low - say, under 10 dB, you might have a transmitted signal strength problem. Check your connector is tight.

You can also check your transmitted power by loading https://ktrax.kisstech.ch/flarm-liverange and inputing your 6 digit hex ICAO code from your flarmcfg.txt file. If you were tracked on OGN, it will give you a plot of signal strength received vs range in km, plotted in blue, versus the average performance of all flarms detected, plotted in green. It gives you a plot of performance in the last week or two. If you want to see what it looks like, take a look at mine, C081B6 (SZD-55, so no carbon in it).

If you see low power on the first test, and low received power at the OGN stations on the second, it might be a bad antenna (the coax doesn't age well, and you should avoid sharp corners). Try replacing it with a new one (keeping a spare around is a good idea) or borrow one from a friend which is known to work well. You might also try swapping PowerFLARM boxes, to see if the antenna or the box is the problem. This is pretty easy in some installations, very hard in others. It can prevent sending a good box in for testing (we don't have a repair facility in Canada, so that adds to the time and money involved).

Your antenna is a dipole (or in some cases, a 1/4 wave antenna which needs a ground plane). In both cases, the antenna should be as close to vertical in flight as possible; this maximizes the signal gain just above and below the horizon - our primary threats. Richard's comments on carbon fibre or metal gliders shielding transmissions is correct, and we should push manufacturers into building flarm antenna locations that give good RF 'visibility' in all directions into the high performing and very spendy gliders they have for sale, though that won't fix the problem for many, many years. Some factories are doing this now, some don't seem to be.

Also, you should be running the latest PowerFLARM firmware version (7.21, released in May 2023).

Cheers
Dan

[Richard Pfiffner]

Dan,

I tried the ktrax on a flarm that I recently repaired. Had to replace the Xmit & receive board you know the bottom board that requires total disassembly.

I believe the Ktrax is only transmit specifications from the client. The powerflarm that had to be repaired: db had inconsistent readings of 10db to 15db from 0 to 5000 meters and below 10 db starting at 10000 meters after 10000m 5db and below.

The unit did not meet any of the Flarm transmit and receive specifications.

On the other hand my PowerFlarm that met all the Flarm test specifications showed 22db at 5000 meters and 15db at 25000 meters.

There are about 41 test specifications that have to be tested for a complete Powerflarm test. Equipment used: Spectrum analyzer, signal generator, terminal program, test firmware and variable power supply that can measure amp draw.
When a board is replaced you have to run the test again.

Thanks
Richard
www.craggyaero.com

[kinsell]

On 7/1/23 10:44 AM, Dan Daly wrote:

> Your antenna is a dipole (or in some cases, a 1/4 wave antenna which needs a ground plane). In both cases, the antenna should be as close to vertical in flight as possible; this maximizes the signal gain just above and below the horizon - our primary threats. Richard's comments on carbon fibre or metal gliders shielding transmissions is correct, and we should push manufacturers into building flarm antenna locations that give good RF 'visibility' in all directions into the high performing and very spendy gliders they have for sale, though that won't fix the problem for many, many years. Some factories are doing this now, some don't seem to be.
>

I just got back from a big glider event where some people were
complaining about poor PF performance.

It's become popular to install quarter wave whips on the glare shield,
along with a ground plane on the bottom side of the shield.
Unfortunately, people have gone overboard on the ground planes. If a
small one is good, a huge one must be better! I saw several that were
at least 7 x 7 inches.

Unfortunately, they were forgetting about GPS antennas that were mounted
down lower behind the panel. One guy had a GPS antenna directly below
the ground plane! His PF sorta worked, but kept dropping in and out.

Flarms, Hawks, and other beloved electronics won't work at all without
good GPS reception. We remounted the gps forward to get it out of the
shadow of the ground plane, and he immediately reported much better
performance. Hard to believe, but sometimes fixing one problem can
create others.

I fly a 26E, which has aramid in the nose apparently for crash
protection. A single dipole antenna down at the left rudder pedal works
well. It's not an optimal position, but good enough. It doesn't let me
leach gliders at 40 miles, but I find collision avoidance for those
targets isn't needed.

-Dave

[Richard Pfiffner]

Dave,

I have found that the max flarm range is 5 to 8 NM , any thing over that is ADSB targets

Richard

[Richard Pfiffner]

I have two dipole antennas Flarm B and ADSB in the nose of my ventus b it is fiberglass and they work well.
They are spaced out away from the glass with dual lock. to prevent tips touching the fiberglass. Flarm mentions to keep tips away from surface to prevent static discharge damage.

Richard

[Dan Marotta]

We're not al born electrical engineers; some of us actually had to go to
school!

My Stemme is al carbon so I mounted the "A" and the ADS-B antennae on
top of the glare shield and I installed an external blade antenna on the
bottom of the propeller dome. Seems to work OK.

Dan
5J

[George Haeh]

In my ASW-27 I mount long antennas on the canopy sides with foam blocks to ensure the tips are at least ¼" clear. Photos and range analysis:

https://drive.google.com/drive/folders/168KoRlGOxWECzXIVwmaEthaHP9KMHJ-G

On some 2-seaters the fibreglass bow between the canopies is a good location.

Human bodies and hardware bits block transmission. Antenna placement on both sides or opposite ends of the cockpit can mitigate.

[Hank Nixon]

On Saturday, July 1, 2023 at 10:52:18 AM UTC-4, Richard Pfiffner wrote:

John Godfrey did some testing and found that tight radius bends in antennas tend to have a bad effect on range.
UH

[Davis Chappins]

I wonder if adding something like this https://v3.airspy.us/product/upu-fp915s/ to amplify the signal would help range? I include this in all of my OGN kits and it filters and boosts by 16db consuming only 50mA. I have a spare one I plan to try on my PF antenna B which is passive (rx only).

[Richard Livingston]

On Tuesday, September 5, 2023 at 12:04:03 AM UTC-5, Davis Chappins wrote:
> I wonder if adding something like this https://v3.airspy.us/product/upu-fp915s/ to amplify the signal would help range? I include this in all of my OGN kits and it filters and boosts by 16db consuming only 50mA. I have a spare one I plan to try on my PF antenna B which is passive (rx only).

The problem with that preamplifier is that powerflarm transmits and receives on the same antenna. This preamplifier can't handle the transmit.

Rich L.

[Davis Chappins]

>> The problem with that preamplifier is that powerflarm transmits and receives on the same antenna. This preamplifier can't handle the transmit.

>I plan to try on my PF antenna B which is passive (rx only)

To connect it to PF antenna A or either on PF Fusion (which tx/rx on both antennas) you could use https://v3.airspy.us/product/upu-fp915sb/

[Moshe Braner]

On 9/5/2023 1:04 AM, Davis Chappins wrote:
> I wonder if adding something like this https://v3.airspy.us/product/upu-fp915s/ to amplify the signal would help range? I include this in all of my OGN kits and it filters and boosts by 16db consuming only 50mA. I have a spare one I plan to try on my PF antenna B which is passive (rx only).
>

I'd be curious if that helps. But I think the main limit to reception
range on a FLARM is the poor antenna. There isn't room in a glider for
a really good antenna, which needs to be about 3 feet tall - like the
ones (12 dB) typically used in OGN ground stations. A compromise
antenna that is about half that long (8 dB?) may be worth a try. If
your goal is to receive FLARM signals from far away.

Remember that FLARM was designed for short-range collision avoidance,
not long-range "radar". It is cool that despite that, and the poor
antennas, we often "see" each other from 5, 10, 20 miles away. And OGN
ground stations in open locations and with good antennas (and the
pre-amp) can receive FLARM transmissions (about 1/40-th of a watt!) from
up to 100 miles away.

[Tim Newport-Peace]

Just making the antenna longer will not help. Quite the reverse.
The OGN antennas are collinear, which is in effect several antennas
mounted on top of each other. Each section being half-lambda long except
at the top.

Look at http://live.glidernet.org/doc/collinear_antenna.pdf

[Richard Livingston]

This device might work with Flarm, but you should check it out carefully to make sure.
There is great potential for corrupting the transmissions if the device does not switch
from Rx to Tx mode quickly enough. If that is not done quickly enough your Flarm may
not be intelligible by other Flarms and thus you would not be "seen" by other Flarms.

Rich L