Flarm reporting my own ADSB Out

[[email protected]]

Greetings,

Installed my new Trig and TN72 and today when I powered up both my Flarm and the Trig, the Flarmview reported my own ADSB Out signal as a ADSB target.

PowerFlarm Core - 6.42 Firmware
Flarmview - 2.39 Firmware

Flarm Config ID shows identical to ADSB Out ID

FlarmView is showing my target as my contest number so it's correctly matching my ADSB Out ID to my contest number based on current FlarmNet.

Flarmview shows correct Flarm ID when Flarm -> Configuration is selected.


Am I missing something? Is this a PowerFlarm issue or a FlarmView issue? I was expecting that the Flarm/FlarmView would ignore my own signal based on the ID.

All of this was stationary on the ground testing, but I doubt that it would be different if I was flying.

Thanks for any help or advice.

Mark

[Dan Daly[_2_]]

On Saturday, March 10, 2018 at 9:29:57 PM UTC-5, wrote:
> Greetings,
>
> Installed my new Trig and TN72 and today when I powered up both my Flarm and the Trig, the Flarmview reported my own ADSB Out signal as a ADSB target.
>
> PowerFlarm Core - 6.42 Firmware
> Flarmview - 2.39 Firmware
>
> Flarm Config ID shows identical to ADSB Out ID
>
> FlarmView is showing my target as my contest number so it's correctly matching my ADSB Out ID to my contest number based on current FlarmNet.
>
> Flarmview shows correct Flarm ID when Flarm -> Configuration is selected.
>
>
> Am I missing something? Is this a PowerFlarm issue or a FlarmView issue? I was expecting that the Flarm/FlarmView would ignore my own signal based on the ID.
>
> All of this was stationary on the ground testing, but I doubt that it would be different if I was flying.
>
> Thanks for any help or advice.
>
> Mark

Hi Mark - here are some settings you may wish to look at in your flarmcfg.txt file:

################################################## ######################
# transponder and PCAS configuration
################################################## ######################

# do Mode C signal processing, ie, PCAS mode (0=no, 1=yes)
$PFLAC,S,MODEC,1

# own Mode C signal filtering (to eliminate your own xpdr)
# 0=aggressive (use w/ Mode C Xpdr), 1=normal (no Xpdr or Mode S)
# normal sometimes results in false PCAS alerts about every 10 min
$PFLAC,S,OWNMODEC,1

# PCAS antenna gain (30=default, higher makes PCAS targets closer)
$PFLAC,S,PCASCALIBRATION,30

# transponder type (0=None, 1=Mode C, 2=Mode S)
$PFLAC,S,XPDR,2

# use Mode S barometric altitude for PCAS height calc (0=no, 1=yes)
$PFLAC,S,MODESALT,1

Cheers
Dan

[[email protected]]

Dan,

Thanks! I had not updated the config file to show that I now had the Mode S installed. It’s now working properly.

Mark

[Dan Daly[_2_]]

On Sunday, March 11, 2018 at 8:39:05 AM UTC-4, wrote:
> Dan,
>
> Thanks! I had not updated the config file to show that I now had the Mode S installed. It’s now working properly.
>
> Mark

No problem, Mark. Glad you have FLARM and glad that it is working.

[Dan Marotta]

Why not use 0=aggressive?

I occasionally see PCAS targets at 0 altitude differential right on top
of me.Â* I assume that's my own ship, but it's very disconcerting to have
that pop up.Â* I'll have to check my config file...

On 3/10/2018 7:46 PM, Dan Daly wrote:
> # own Mode C signal filtering (to eliminate your own xpdr)
> # 0=aggressive (use w/ Mode C Xpdr), 1=normal (no Xpdr or Mode S)
> # normal sometimes results in false PCAS alerts about every 10 min
> $PFLAC,S,OWNMODEC,1

--
Dan, 5J

[jfitch]

On Sunday, March 11, 2018 at 8:44:54 AM UTC-7, Dan Marotta wrote:
> Why not use 0=aggressive?
>
> I occasionally see PCAS targets at 0 altitude differential right on top
> of me.Â* I assume that's my own ship, but it's very disconcerting to have
> that pop up.Â* I'll have to check my config file...
>
> On 3/10/2018 7:46 PM, Dan Daly wrote:
> > # own Mode C signal filtering (to eliminate your own xpdr)
> > # 0=aggressive (use w/ Mode C Xpdr), 1=normal (no Xpdr or Mode S)
> > # normal sometimes results in false PCAS alerts about every 10 min
> > $PFLAC,S,OWNMODEC,1
>
> --
> Dan, 5J

Probably because if you have Mode S the Flarm can tell it's you, but if you have mode C all it can tell is there is some traffic nearby - perhaps you, or perhaps someone else.

[Dan Marotta]

I have Mode S, but I still get those occasional targets in my lap and
never see any of them...Â* Is there a Mode S filter or does Flarm think
it's smart enough not to need it?

On 3/11/2018 10:27 AM, jfitch wrote:
> On Sunday, March 11, 2018 at 8:44:54 AM UTC-7, Dan Marotta wrote:
>> Why not use 0=aggressive?
>>
>> I occasionally see PCAS targets at 0 altitude differential right on top
>> of me.Â* I assume that's my own ship, but it's very disconcerting to have
>> that pop up.Â* I'll have to check my config file...
>>
>> On 3/10/2018 7:46 PM, Dan Daly wrote:
>>> # own Mode C signal filtering (to eliminate your own xpdr)
>>> # 0=aggressive (use w/ Mode C Xpdr), 1=normal (no Xpdr or Mode S)
>>> # normal sometimes results in false PCAS alerts about every 10 min
>>> $PFLAC,S,OWNMODEC,1
>> --
>> Dan, 5J
> Probably because if you have Mode S the Flarm can tell it's you, but if you have mode C all it can tell is there is some traffic nearby - perhaps you, or perhaps someone else.

--
Dan, 5J

[Dan Daly[_2_]]

On Sunday, March 11, 2018 at 3:54:50 PM UTC-4, Dan Marotta wrote:
> I have Mode S, but I still get those occasional targets in my lap and
> never see any of them...Â* Is there a Mode S filter or does Flarm think
> it's smart enough not to need it?

There is a Mode S filter if you set it in flarmcfg.txt.

# transponder type (0=None, 1=Mode C, 2=Mode S)
$PFLAC,S,XPDR,2

Confirm your ICAO address in the Mode S transponder and FLARM ID ($PFLAC,S,ID,XXXXXX) are the same.

They continue to work to minimize false alerts, so keeping firmware updated is advised.

Dan

[Dan Marotta]

I did that some time ago, but maybe a later config file left that off.Â*
Thanks for the pointer.

On 3/11/2018 2:16 PM, Dan Daly wrote:
> On Sunday, March 11, 2018 at 3:54:50 PM UTC-4, Dan Marotta wrote:
>> I have Mode S, but I still get those occasional targets in my lap and
>> never see any of them...Â* Is there a Mode S filter or does Flarm think
>> it's smart enough not to need it?
> There is a Mode S filter if you set it in flarmcfg.txt.
>
> # transponder type (0=None, 1=Mode C, 2=Mode S)
> $PFLAC,S,XPDR,2
>
> Confirm your ICAO address in the Mode S transponder and FLARM ID ($PFLAC,S,ID,XXXXXX) are the same.
>
> They continue to work to minimize false alerts, so keeping firmware updated is advised.
>
> Dan

--
Dan, 5J

[Dirk_PW[_2_]]

Question... Has anyone with a FLARM actually flown close enough to a glider that is outputting both ADS-B and FLARM and verified that only one aircraft appears on their display? The glider would have to be in range of the FLARM to ensure that both signals are hitting the front end of the FLARM.

[Darryl Ramm]

On Wednesday, March 21, 2018 at 11:14:28 AM UTC-7, Dirk_PW wrote:
> Question... Has anyone with a FLARM actually flown close enough to a glider that is outputting both ADS-B and FLARM and verified that only one aircraft appears on their display? The glider would have to be in range of the FLARM to ensure that both signals are hitting the front end of the FLARM.

Yes PowerFLARM 1090ES In and FLARM deduplication works. Why the question? If it's not working the likely suspect is the FLARM or transponder have mismatching ICAO addresses.

[Dirk_PW[_2_]]

My question was largely curiosity. I see validation about 'own ship' duplication but nothing about 'off board' duplication when a different receiver is sensing two separate signals with the same ICAO address. Good to know it is working. With all this great info that has been shared I think I'm going to move forward with a TABS ADS-B install. Thanks for all the time spent researching and sharing this info.

BTW, it begs the question whether it would make sense to have the ability to turn off the FLARM xmtr if you are already outputting ADS-B out, and everyone you fly with has at least a PowerFlarm and can sense the 1090ES signal.. It would cut down on unneeded transmission (and reduce battery power consumption). Thoughts there?

[[email protected]]

On Wednesday, March 21, 2018 at 12:46:21 PM UTC-7, Darryl Ramm wrote:
> Yes PowerFLARM 1090ES In and FLARM deduplication works. Why the question?
> If it's not working the likely suspect is the FLARM or transponder have mismatching ICAO addresses.

It's still spotty deduplicating Mode S and FLARM. A friend and I have flown together several times and the false alerts can get annoying. We both have LX9000 and Trig transponders. We've gone over and over the configs and have been in touch with FLARM and LXnav. The answer is that they're still working on such issues and future firmware may get better.

We flew together last Sunday, and both still get occasional PCAS warnings complete with the contest number while at the same time seeing the FLARM target. I also get self alerts every 20-30 minutes or so.

5Z

[Ramy[_2_]]

I am not aware of mode S and flarm deduplication so what you see is expected behavior. The problem is in the LX9000 side as I pointed out in another thread. They promised to have an option to turn off PCAS collision alarm from mode c/s which is what you need. You will still get timely alerts but not annoying alarm if they implement it correctly.
ADSB is a different case. Flarm suppose to ignore the ADSB signal when receiving flarm signal. I sure hope it is working as expected. If not I will find out soon that I am driving my buddies crazy when thermaling together.

Ramy

[Darryl Ramm]

On Wednesday, March 21, 2018 at 7:15:00 PM UTC-7, Ramy wrote:
> I am not aware of mode S and flarm deduplication so what you see is expected behavior. The problem is in the LX9000 side as I pointed out in another thread. They promised to have an option to turn off PCAS collision alarm from mode c/s which is what you need. You will still get timely alerts but not annoying alarm if they implement it correctly.
> ADSB is a different case. Flarm suppose to ignore the ADSB signal when receiving flarm signal. I sure hope it is working as expected. If not I will find out soon that I am driving my buddies crazy when thermaling together.
>
> Ramy

Mode S PCAS is _supposed_ to deduplicate in the PowerFLARM, a Mode S PCAS alert detects the target aircraft's ICAO address, if the PowerFLARM sees the same ICAO address via ADS-B Out or FLARM it should ignore the PCAS. As I've pointed out before, the main issue with spurious *PCAS* alerts is you can't stop Mode S transponders being interrogated by legacy Mode C (not Mode S capable) interrogators and then your transponder has to reply with an old style Mode C reply with no Mode S ICAO address. And then your PowerFLARM will have a lot harder job of trying to guess if it needs to deduplicate that PCAS traffic vs 1090ES or FLARM warnings. And sure there are lots of room here for things to still not happen properly, including between the PowerFLARM and display (e.g. timing windows between when different signals are received).

The classic example of a device that causes those Mode C interrogations is the Ryan TCAD interrogators still flying around in some GA aircraft, they were Mode C not Mode S capable and an aircraft equipped with one of those within several tens of miles of you may cause these issues with non-deduplicated targets and self-targets. TCAS I and II systems are Mode S interrogators so should not do this.

This discussion has already got to confusing levels. Are we talking FLARM actual warnings or LXNav handling of them. 1090ES traffic or PCAS etc. I've gotten lost. And really belongs in a discussion with the appropriate vendors, as we all see to be agreeing on.