PowerFlarm “Own Transponder Detection" Rate

[John Carlyle]

I’ve been trying to get the rate of "own transponder detection" by my PowerFlarm Core as low as possible. Nothing I’ve done has improved it beyond roughly every 10 minutes, on average. Sometimes it’s much worse, showing up almost constantly. Turning off PCAS isn’t really an option for me, so I’d like to know if it’s possible to get a lower false alarm rate.

QUESTION - If you have a PowerFlarm with the PCAS function turned on, what false alarm rate are you getting? If the period is longer than 10 minutes, what did you do to get it (configuration settings, antenna placement, area you fly in)?

For reference, I’ve been working on this problem in both my old LS-8 (with a Mode S) and my new one (with a Mode C). Both ships used the same PowerFlarm configuration file settings, except for XPDR and MODESALT (both were set correctly for each ship). OWNMODEC was set to Aggressive in both ships. The PowerFlarm and transponder antennas were in the same position in both ships (glare shield and tail boom, respectively) and the PowerFlarm Core was the exact same unit for both ships, too.

-John, Q3

[Dan Marotta]

Not that I can help but I haven't experienced that problem with my
Stemme. My transponder antenna is on the under side of the carbon nose
bowl and the PF antennae are on top of the glare shield. Maybe the
carbon blocks the transponder signal so the PF doesn't "see" it directly.

On 7/12/2017 8:34 AM, John Carlyle wrote:
> I’ve been trying to get the rate of "own transponder detection" by my PowerFlarm Core as low as possible. Nothing I’ve done has improved it beyond roughly every 10 minutes, on average. Sometimes it’s much worse, showing up almost constantly. Turning off PCAS isn’t really an option for me, so I’d like to know if it’s possible to get a lower false alarm rate.
>
> QUESTION - If you have a PowerFlarm with the PCAS function turned on, what false alarm rate are you getting? If the period is longer than 10 minutes, what did you do to get it (configuration settings, antenna placement, area you fly in)?
>
> For reference, I’ve been working on this problem in both my old LS-8 (with a Mode S) and my new one (with a Mode C). Both ships used the same PowerFlarm configuration file settings, except for XPDR and MODESALT (both were set correctly for each ship). OWNMODEC was set to Aggressive in both ships. The PowerFlarm and transponder antennas were in the same position in both ships (glare shield and tail boom, respectively) and the PowerFlarm Core was the exact same unit for both ships, too.
>
> -John, Q3

--
Dan, 5J

[[email protected]]

I disabled mine for the Nephi OLC event, but would also like to have it actually work right. My old MRX PCAS was very reliable in this situation.

What I see is bursts of self alerts then a few hours of silence, followed by another spurt of warnings. Easy enough to identify due to the very short range and altitude less than 50'.

Maybe what we need is an option to filter out any PCAS target less than 1/2 km since by then a warning is not likely to help?

5Z

[John Cochrane[_3_]]

I had this problem. It means that your powerflarm configuration file is not properly set with your own transponder code. If properly set, it always ignores your own transponder.

[JS]

On Wednesday, July 12, 2017 at 9:58:05 AM UTC-7, John Cochrane wrote:
> I had this problem. It means that your powerflarm configuration file is not properly set with your own transponder code. If properly set, it always ignores your own transponder.

I'd hesitate to use the term "always".
Due to alerts of collisions with myself even after correcting a hex address problem, I have disabled Mode C alerts.
In this way I can continue to ignore the thing and use LookOutTheWindow.com unless something serious is happening. Mode C reporting seems a nuisance, especially in a thermal with other transponder equipped glider(s).
Jim

[John Carlyle]

Thanks, Dan. At least I know someone has found a way to get to a point where there are no PCAS false alarms! But I really have to ask - do you see any PCAS alerts for other aircraft?

-John, Q3

On Wednesday, July 12, 2017 at 11:54:11 AM UTC-4, Dan Marotta wrote:
> Not that I can help but I haven't experienced that problem with my
> Stemme. My transponder antenna is on the under side of the carbon nose
> bowl and the PF antennae are on top of the glare shield. Maybe the
> carbon blocks the transponder signal so the PF doesn't "see" it directly.
>
> On 7/12/2017 8:34 AM, John Carlyle wrote:
> > I’ve been trying to get the rate of "own transponder detection" by my PowerFlarm Core as low as possible. Nothing I’ve done has improved it beyond roughly every 10 minutes, on average. Sometimes it’s much worse, showing up almost constantly. Turning off PCAS isn’t really an option for me, so I’d like to know if it’s possible to get a lower false alarm rate.
> >
> > QUESTION - If you have a PowerFlarm with the PCAS function turned on, what false alarm rate are you getting? If the period is longer than 10 minutes, what did you do to get it (configuration settings, antenna placement, area you fly in)?
> >
> > For reference, I’ve been working on this problem in both my old LS-8 (with a Mode S) and my new one (with a Mode C). Both ships used the same PowerFlarm configuration file settings, except for XPDR and MODESALT (both were set correctly for each ship). OWNMODEC was set to Aggressive in both ships. The PowerFlarm and transponder antennas were in the same position in both ships (glare shield and tail boom, respectively) and the PowerFlarm Core was the exact same unit for both ships, too.
> >
> > -John, Q3
>
> --
> Dan, 5J

[John Carlyle]

I don't think that's my problem, John. When I had a Mode S transponder I still got false PCAS alerts, even with the Mode S code being identical (as in, copied and pasted from the FAA site into the PF config, and then cross-checked with what the Trig 21 displayed). A Mode C transponder doesn't output the Mode S code, so the code doesn't help the PowerFlarm identifying my transponder signal. The Mode S code for my new glider that is in my PF config file is transmitted by the Flarm so my glider can be IDed by other Flarm users who loaded FlarmNet.

-John, Q3

On Wednesday, July 12, 2017 at 12:58:05 PM UTC-4, John Cochrane wrote:
> I had this problem. It means that your powerflarm configuration file is not properly set with your own transponder code. If properly set, it always ignores your own transponder.

[Steve Koerner]

I'm quite sure that wrong transponder code is not my problem either. There is some sort of fallacy in the operation. It's quite irritating. Sometimes it seems that I can clear it by cycling power.

[[email protected]]

I wish I had a solution, but I also disabled PCAS alerts on my Flarm due to annoying false alarms.

If have a Zaon PCAS which works great and I like the numerical display better than the rings on the Flarmview.

Mark

[Andrzej Kobus]

On Wednesday, July 12, 2017 at 10:35:02 AM UTC-4, John Carlyle wrote:
> I’ve been trying to get the rate of "own transponder detection" by my PowerFlarm Core as low as possible. Nothing I’ve done has improved it beyond roughly every 10 minutes, on average. Sometimes it’s much worse, showing up almost constantly. Turning off PCAS isn’t really an option for me, so I’d like to know if it’s possible to get a lower false alarm rate.
>
> QUESTION - If you have a PowerFlarm with the PCAS function turned on, what false alarm rate are you getting? If the period is longer than 10 minutes, what did you do to get it (configuration settings, antenna placement, area you fly in)?
>
> For reference, I’ve been working on this problem in both my old LS-8 (with a Mode S) and my new one (with a Mode C). Both ships used the same PowerFlarm configuration file settings, except for XPDR and MODESALT (both were set correctly for each ship). OWNMODEC was set to Aggressive in both ships. The PowerFlarm and transponder antennas were in the same position in both ships (glare shield and tail boom, respectively) and the PowerFlarm Core was the exact same unit for both ships, too.
>
> -John, Q3

This is a common problem and it exists even with proper configuration. I think, it is an issue with PF hardware stability. If you look into log files you will find some interesting entries there. I guess I am lucky enough to only see an issue every 20-30 min. I would suggest experimenting with better PF antenna, but that is probably the only thing that can be done. I would also try to position the PF unit and run the antenna cable is such a way that there is minimal interference from other devices. I gave up. Short antenna cable can also cause a problem.

[Dan Marotta]

Yes, I do see PCAS alerts. And, having read more of this thread, I
believe I'm suffering from this as well. I occasionally get a PCAS
alert at +00 altitude and on top of my location. I've looked like crazy
and never seen another aircraft that close so I guess I can assume that
I'm getting a false alarm, too. I'll look at my config file and see if
I left something out.

On 7/12/2017 12:08 PM, John Carlyle wrote:
> Thanks, Dan. At least I know someone has found a way to get to a point where there are no PCAS false alarms! But I really have to ask - do you see any PCAS alerts for other aircraft?
>
> -John, Q3
>
> On Wednesday, July 12, 2017 at 11:54:11 AM UTC-4, Dan Marotta wrote:
>> Not that I can help but I haven't experienced that problem with my
>> Stemme. My transponder antenna is on the under side of the carbon nose
>> bowl and the PF antennae are on top of the glare shield. Maybe the
>> carbon blocks the transponder signal so the PF doesn't "see" it directly.
>>
>> On 7/12/2017 8:34 AM, John Carlyle wrote:
>>> I’ve been trying to get the rate of "own transponder detection" by my PowerFlarm Core as low as possible. Nothing I’ve done has improved it beyond roughly every 10 minutes, on average. Sometimes it’s much worse, showing up almost constantly. Turning off PCAS isn’t really an option for me, so I’d like to know if it’s possible to get a lower false alarm rate.
>>>
>>> QUESTION - If you have a PowerFlarm with the PCAS function turned on, what false alarm rate are you getting? If the period is longer than 10 minutes, what did you do to get it (configuration settings, antenna placement, area you fly in)?
>>>
>>> For reference, I’ve been working on this problem in both my old LS-8 (with a Mode S) and my new one (with a Mode C). Both ships used the same PowerFlarm configuration file settings, except for XPDR and MODESALT (both were set correctly for each ship). OWNMODEC was set to Aggressive in both ships. The PowerFlarm and transponder antennas were in the same position in both ships (glare shield and tail boom, respectively) and the PowerFlarm Core was the exact same unit for both ships, too.
>>>
>>> -John, Q3
>> --
>> Dan, 5J

--
Dan, 5J

[Ramy[_2_]]

I have a mode C transponder and never had a false alert from my own transponder, not even once in the 1500 hours or so that I have with powerflarm.

Ramy

[John Carlyle]

Wow, Ramy, sounds like you found the magic! Would you kindly share some details?
1. Contents of your PowerFlarm config file
2. Type and location of your Flarm antennas
3. Location of your transponder antenna
A lot of us would dearly love to be able to duplicate your amazing results.

-John, Q3

On Thursday, July 13, 2017 at 3:24:15 AM UTC-4, Ramy wrote:
> I have a mode C transponder and never had a false alert from my own transponder, not even once in the 1500 hours or so that I have with powerflarm.
>
> Ramy

[Ramy[_2_]]

1- Both powerflarm antennas in the nose (no carbon in the nose section of my 27a).
2- transponder antenna under the seat pan in front of the stick (so not far from the powerflarm antenna, maybe 3 feet at the most.
3 - configuration file may need to wait until next week or so. BTW I recall there is an option to suppress own transponder more aggressively, I just used the default.

I really never had false alert from my own transponder, no kidding. And my mode C alert is working very well.

Ramy

[John Carlyle]

Many thanks, Ramy. What you have doesn't seem too different from my set-up, except I have about 8 feet separation between the transponder antenna and the Flarm ADS-B antenna in a fiberglass fuselage ship. Perhaps the 27's carbon fuselage does some helpful attenuation of your own transponder signal?

I look forward to seeing your configuration file. OWNMODEC in my configuration file is set to Aggressive (= 0). I don't know whether this is the default value.

Do other 27/29 owners who are seeing false Mode C alerts have their transponder and Flarm antennas mounted similarly to Ramy's?

-John, Q3

On Friday, July 14, 2017 at 2:14:58 AM UTC-4, Ramy wrote:
> 1- Both powerflarm antennas in the nose (no carbon in the nose section of my 27a).
> 2- transponder antenna under the seat pan in front of the stick (so not far from the powerflarm antenna, maybe 3 feet at the most.
> 3 - configuration file may need to wait until next week or so. BTW I recall there is an option to suppress own transponder more aggressively, I just used the default.
>
> I really never had false alert from my own transponder, no kidding. And my mode C alert is working very well.
>
> Ramy

[Ramy[_2_]]

On Friday, July 14, 2017 at 7:31:21 AM UTC-7, John Carlyle wrote:
> Many thanks, Ramy. What you have doesn't seem too different from my set-up, except I have about 8 feet separation between the transponder antenna and the Flarm ADS-B antenna in a fiberglass fuselage ship. Perhaps the 27's carbon fuselage does some helpful attenuation of your own transponder signal?
>
> I look forward to seeing your configuration file. OWNMODEC in my configuration file is set to Aggressive (= 0). I don't know whether this is the default value.
>
> Do other 27/29 owners who are seeing false Mode C alerts have their transponder and Flarm antennas mounted similarly to Ramy's?
>
> -John, Q3
>
> On Friday, July 14, 2017 at 2:14:58 AM UTC-4, Ramy wrote:
> > 1- Both powerflarm antennas in the nose (no carbon in the nose section of my 27a).
> > 2- transponder antenna under the seat pan in front of the stick (so not far from the powerflarm antenna, maybe 3 feet at the most.
> > 3 - configuration file may need to wait until next week or so. BTW I recall there is an option to suppress own transponder more aggressively, I just used the default.
> >
> > I really never had false alert from my own transponder, no kidding. And my mode C alert is working very well.
> >
> > Ramy

Here is the relevant part of my config file. The rest is default.

$pflac,s,acft,1
$pflac,s,xpdr,1
$pflac,s,id,XXXXXX
$pflac,s,pcasvrange,600
$pflac,s,pcasrange,5000

Ramy

[John Carlyle]

Hi, Ramy,
Thanks for posting those configuration values. The important PCAS parameters to which you are defaulting are:
Modesalt - default is 1 (get altitude from Mode S signal)
Ownmodec - default is 0 (aggressive mode used with Mode C transponder)
Modec - default is 1 (enable processing of Mode C targets, ie, PCAS)
Since you don’t get false alerts from your own transponder you probably don’t want to “fix” things. But you really should put the command $PFLAC,S,MODESALT,0 into your configuration file, since you have a Mode C transponder. This will not only read altitude values from the PF internal pressure sensor, the altitude will be much less quantized than the 100 foot intervals in a Mode S signal. Right now you are configure to sometimes getting an altitude value from a stray Mode S signal.

-John, Q3

On Friday, July 21, 2017 at 1:20:39 AM UTC-4, Ramy wrote:
> On Friday, July 14, 2017 at 7:31:21 AM UTC-7, John Carlyle wrote:
> > Many thanks, Ramy. What you have doesn't seem too different from my set-up, except I have about 8 feet separation between the transponder antenna and the Flarm ADS-B antenna in a fiberglass fuselage ship. Perhaps the 27's carbon fuselage does some helpful attenuation of your own transponder signal?
> >
> > I look forward to seeing your configuration file. OWNMODEC in my configuration file is set to Aggressive (= 0). I don't know whether this is the default value.
> >
> > Do other 27/29 owners who are seeing false Mode C alerts have their transponder and Flarm antennas mounted similarly to Ramy's?
> >
> > -John, Q3
> >
> > On Friday, July 14, 2017 at 2:14:58 AM UTC-4, Ramy wrote:
> > > 1- Both powerflarm antennas in the nose (no carbon in the nose section of my 27a).
> > > 2- transponder antenna under the seat pan in front of the stick (so not far from the powerflarm antenna, maybe 3 feet at the most.
> > > 3 - configuration file may need to wait until next week or so. BTW I recall there is an option to suppress own transponder more aggressively, I just used the default.
> > >
> > > I really never had false alert from my own transponder, no kidding. And my mode C alert is working very well.
> > >
> > > Ramy
>
> Here is the relevant part of my config file. The rest is default.
>
> $pflac,s,acft,1
> $pflac,s,xpdr,1
> $pflac,s,id,XXXXXX
> $pflac,s,pcasvrange,600
> $pflac,s,pcasrange,5000
>
> Ramy

[Ramy[_2_]]

John my guess is that since I am configure for mode C, powerflarm is smart enough to ignore the mode S altitude default. I believe this was my conclusion at the time when I first configured my powerflarm. My config file is based on their sample config file which was provided before the config tool was available.
The altitude difference readings I get are very accurate based on flying with gliders with transponder and flames the numbers are always very close (and the distance is also impressively accurate even though it is only estimated based on strength).

Ramy

[John Carlyle]

I can't argue with success, Ramy! Really appreciate you posting all of your information, it was extremely important to know that PCAS can work properly.

I'm still trying to duplicate your PCAS performance, and thanks to you, Jim Staniforth and Darryl Ramm I now have an idea to test out. Wish me luck - I'll let you know how I get on.

-John, Q3

On Friday, July 21, 2017 at 12:21:08 PM UTC-4, Ramy wrote:
> John my guess is that since I am configure for mode C, powerflarm is smart enough to ignore the mode S altitude default. I believe this was my conclusion at the time when I first configured my powerflarm. My config file is based on their sample config file which was provided before the config tool was available.
> The altitude difference readings I get are very accurate based on flying with gliders with transponder and flames the numbers are always very close (and the distance is also impressively accurate even though it is only estimated based on strength).
>
> Ramy