PowerFlarms at Avenal Contest

Not as exciting as the Brick reports from Mifflin with the new hardware, but we had a good showing of PowerFlarm at Avenal. In total about half the field was equipped with portable units of our own or from the Rental Program through Rex at Williams Soaring. I also put PF in each towplane for the duration of the contest. The tow pilots don't benefit from the audio alert due to the noise, but at least the PF equipped gliders can get a warning.

I think that everyone flying with the PF found them to work very well and an aid to situational awareness. The range of the portable units is a couple of miles under the best scenario, but I continue to be amazed at how well it filters out thermal and non-threat traffic.

Ray Gimmey had one head-to-head scenario on the practice day where he said it gave him the warning he needed to avoid a bad situation.

Antenna placement and setup will be a key factor to consider. On the last day we had one situation while I was on tow with a glider coming towards us.. I had a visual on the other glider the entire time and my flarm was in red alert mode. The other glider unfortunately didn't get an alert. I suspect because we were under his nose where possibly something in the panel was blocking his reception. Or my flat antenna wasn't transmitting as well as his setup. Either way, I got the alert, he didn't.

Overall, nothing but positive comments about what PowerFlarm will do for situational awareness.

Morgan

I would be interested to hear Urs/Flarm’s, or the PF people’s,
reaction to that.

To my simple mind, for you to get an alert, your PF antenna and the
glider’s PF antenna both work on line of sight, so each has to see the
other. It should not be a one way street.

I suppose it is possible that in one direction the signal was just
strong enough and/or not too badly attenuated, and the other less
good. What do the experts say?

Chris N.

On May 22, 3:48*pm, Chris Nicholas wrote:
To my simple mind, for you to get an alert, your PF antenna and the
glider’s PF antenna both work on line of sight, so each has to see the
other. It should not be a one way street.
I suppose it is possible that in one direction the signal was just
strong enough and/or not too badly attenuated, and the other less
good. What do the experts say?

I am hardly an expert, but... yes, an antenna is exactly as effective
while transmitting as it is while receiving. The attenuation
experienced by signal from glider A to glider B is exactly the same as
the one experienced by signal from B to A.

My guesses, in no particular order:
1) Either transmitter power or receiver sensitivity differs between
units. The pilot with less power or more sensitive transmitter will be
the first one to get a warning.
2) One of the gliders has a lousy (noisy) electrical installation.
This effectively decreases receiver sensitivity.
3) One of the antennas is so bad that the transmitter reduces power to
avoid damage (and no, this does not contradict what I wrote at the
very beginning).

Bart

I can only report on what our experience was. Both the towplane and my glider had a PF portable installed. Of course, with the towplane 200ft in front of me it may have been transmitting but not a threat.

My flarm was using the flat panel antenna that came with it. The other glider was using the standard stub antenna so a difference in reception sensitivity or transmit efficiency seems plausible. Additionally, my antenna was on the right side of the aircraft and the approaching glider was quartering head on from the left. So attenuation through my thick head was certainly a potential as well.

Despite imperfect performance I'm finding the device really useful and worth every penny. I'm very confident that the flarm team is on the right track regarding performance and it may just be a matter of time and field trials to knock out the specifics and help provide the best ways of mounting antennas and such for maximum range.

Morgan


On Tuesday, May 22, 2012 4:39:24 PM UTC-7, Bart wrote:
On May 22, 3:48*pm, Chris Nicholas wrote:
To my simple mind, for you to get an alert, your PF antenna and the
glider’s PF antenna both work on line of sight, so each has to see the
other. It should not be a one way street.
I suppose it is possible that in one direction the signal was just
strong enough and/or not too badly attenuated, and the other less
good. What do the experts say?

I am hardly an expert, but... yes, an antenna is exactly as effective
while transmitting as it is while receiving. The attenuation
experienced by signal from glider A to glider B is exactly the same as
the one experienced by signal from B to A.

My guesses, in no particular order:
1) Either transmitter power or receiver sensitivity differs between
units. The pilot with less power or more sensitive transmitter will be
the first one to get a warning.
2) One of the gliders has a lousy (noisy) electrical installation.
This effectively decreases receiver sensitivity.
3) One of the antennas is so bad that the transmitter reduces power to
avoid damage (and no, this does not contradict what I wrote at the
very beginning).

Bart

On Tuesday, May 22, 2012 4:57:58 PM UTC-7, Morgan wrote:
I can only report on what our experience was. Both the towplane and my glider had a PF portable installed. Of course, with the towplane 200ft in front of me it may have been transmitting but not a threat.

My flarm was using the flat panel antenna that came with it. The other glider was using the standard stub antenna so a difference in reception sensitivity or transmit efficiency seems plausible. Additionally, my antenna was on the right side of the aircraft and the approaching glider was quartering head on from the left. So attenuation through my thick head was certainly a potential as well.

Despite imperfect performance I'm finding the device really useful and worth every penny. I'm very confident that the flarm team is on the right track regarding performance and it may just be a matter of time and field trials to knock out the specifics and help provide the best ways of mounting antennas and such for maximum range.

Morgan


On Tuesday, May 22, 2012 4:39:24 PM UTC-7, Bart wrote:
On May 22, 3:48*pm, Chris Nicholas wrote:
To my simple mind, for you to get an alert, your PF antenna and the
glider’s PF antenna both work on line of sight, so each has to see the
other. It should not be a one way street.
I suppose it is possible that in one direction the signal was just
strong enough and/or not too badly attenuated, and the other less
good. What do the experts say?

I am hardly an expert, but... yes, an antenna is exactly as effective
while transmitting as it is while receiving. The attenuation
experienced by signal from glider A to glider B is exactly the same as
the one experienced by signal from B to A.

My guesses, in no particular order:
1) Either transmitter power or receiver sensitivity differs between
units. The pilot with less power or more sensitive transmitter will be
the first one to get a warning.
2) One of the gliders has a lousy (noisy) electrical installation.
This effectively decreases receiver sensitivity.
3) One of the antennas is so bad that the transmitter reduces power to
avoid damage (and no, this does not contradict what I wrote at the
very beginning).

Bart

Morgan

I'm surprised others have not asked this yet but to be clear - you had the flat antenna connected to the "FLARM A" connector right? The "A" connector is transmit and receive, the "B" connector is receive only. The flat antenna is normally connected to the "B" port as a receive only diversity antenna.. If you incorrectly had the flat antenna connected to the ADS-B "B"connector and nothing on the "A" connector you will be receive only and that would of course explain why you saw a threat but another glider did not see you. If this was the problem it would be nice to followup with a nice warning on ras for others.

And in general you might be better off using the standard helical antenna (if it will fit with the antenna vertical). The small flat antenna and relatively long thin cable has got to add more loss here compared to the helical (which may be slightly higher gain antenna that the flat one anyhow - but I don't know either antenna specs).

If that was not the problem, then as Bart says the reciprocal principle means that an antenna (or pair of antennas) behaves the same transmitting and receiving. So the loss paths both ways should be the same. The guesses as to what might be happening look good to me as well...

Either way its great to see PowerFLARM being used at the Avenal contests and more pilots getting exposed to its benefits.

Darryl

This was my first contest with PF (Brick on order... rented the mobile PF) and my impressions are similar to Morgan's.

The alarms for dangerous situations give you an acoustic warning and this did get my eyes outside the cockpit. When the acoustic beeping frequency increases there is a VERY DANGEROUS possible collision situation. On the first day, I was alerted to a "head on" DANGEROUS ALERT. I was able to spot the conflicting glider beforehand which passed 100-200ft almost overhead.

The PF display and alerts are not obtrusive and amazingly do not go off even in gaggles... unless there is a conflict. When beeping starts your REALLY need to get your attention outside the cockpit.

PF is definitely worthwhile.. and not distracting in flight unless there is something serious going out. Range seemed to be around 2sm maybe a little better...more than adequate for collision advisories.

Walt Rogers, WX

On Tuesday, May 22, 2012 9:01:52 AM UTC-7, Morgan wrote:
Not as exciting as the Brick reports from Mifflin with the new hardware, but we had a good showing of PowerFlarm at Avenal. In total about half the field was equipped with portable units of our own or from the Rental Program through Rex at Williams Soaring. I also put PF in each towplane for the duration of the contest. The tow pilots don't benefit from the audio alert due to the noise, but at least the PF equipped gliders can get a warning.

I think that everyone flying with the PF found them to work very well and an aid to situational awareness. The range of the portable units is a couple of miles under the best scenario, but I continue to be amazed at how well it filters out thermal and non-threat traffic.

There are a few reasons that one PF equipped aircraft might "alert" while the other conflicting aircraft doesn't.

In a perfect world it should be a two way street. However, the installation or placement of an antenna for transmitting is more critical than that for a recieve antenna. If glider #1's PF antenna is installed less optimally than glider #2's PF antenna, it may well be that #1 gets the alert while #2 does not. As #1's poor antenna install may receive marginally well, but wastes transmit power due to a high SWR or a null due to blocking structure.

Also, the use of the "optional" included flat plate receive-only antenna will improve reception for its user, but has no effect at all on the reception in the other aircraft. The PF in the glider without the flat plate antenna could then trigger alerts in the other glider while not displaying an alert on its own screen.

I hope this makes more sense to y'all than it does to me re-reading it.

bumper

On May 23, 10:47*pm, bumper wrote:
There are a few reasons that one PF equipped aircraft might "alert" while the other conflicting aircraft doesn't.

In a perfect world it should be a two way street. However, the installation or placement of an antenna for transmitting is more critical than that for a recieve antenna. If glider #1's PF antenna is installed less optimally than glider #2's PF antenna, it may well be that #1 gets the alert while #2 does not. As #1's poor antenna install may receive marginally well, but wastes transmit power due to a high SWR or a null due to blocking structure.


Oh. PF uses one antenna to transmit and another to receive?

Bart

On Thursday, May 24, 2012 12:17:13 PM UTC-4, Bart wrote:
On May 23, 10:47*pm, bumper wrote:
There are a few reasons that one PF equipped aircraft might "alert" while the other conflicting aircraft doesn't.

In a perfect world it should be a two way street. However, the installation or placement of an antenna for transmitting is more critical than that for a recieve antenna. If glider #1's PF antenna is installed less optimally than glider #2's PF antenna, it may well be that #1 gets the alert while #2 does not. As #1's poor antenna install may receive marginally well, but wastes transmit power due to a high SWR or a null due to blocking structure.


Oh. PF uses one antenna to transmit and another to receive?

Bart

Not quite. PowerFLARM uses up to 4 antennas. One mandatory for GPS, one mandatory for Mode C/S and ADS-B. The remaining 2 are for FLARM. One FLARM antenna is mandatory, and does transmit/receive functions. It needs to be mounted high up on the glare shield, just under the canopy and preferably near the glareshield lip near the pilot to get maximum performance. The other FLARM antenna is optional, and is receive only. Suggested mounting is aft of the gear, away from transponder and comm antennas, to get better coverage for FLARM ships coming from below and aft. Easy in a fiberglass ship, tricky in a carbon fiber ship.

-John

Lets nip any possible confusion about this in the bud. PowerFLARM has two FLARM antennas "FLARM A" that transmits and receives and "FLARM B" that is receive only. FLARM B is intended to help provide better visibility of threats in otherwise areas/directions of less visibility of the "FLARM A" antenna. In this case Morgan was using the flat antenna (usually shipped for use with the "FLARM B" port) connected to the FLARM A port (so it was transmitting and receiving) with nothing connected to the "FLARM B" port.

Sorry Bumper I'm not following your post. And anyhow this may or may not have anything to do with RF properties. A really nice thing with FLARM and PowerFLARM is the logging capabilities (currently done internally) that allow these type things to be understood. I am not sure this one question justifies spending a lot of the developers time on right now. It will be nice as well when the user visible logs are available that allow end users to check device+antenna sensitivity/range as with Flarm classic devices.

Darryl