Ghost Images on PowerFLARM?

Using a Portable PowerFLARM the first time a few weeks ago I noticed that there were sometimes two targets for a given glider. When I first got near the glider and it showed up on the screen, it was a "hard" target on the built-in display. Once I was in the thermal, however, sometimes that hard target would be supplemented by a ghostly image near it. I was wondering if that was the previous target that the FLARM was trying and failing to verify without processing that the "new" target was the same one that had been displayed some seconds before.

Anyone had this happen? It wasn't a big deal at the time but I'm a little concerned it would/will be with 50 gliders around at Elmira.

Chip Bearden
ASW 24 "JB"
U.S.A.

On Wednesday, July 22, 2015 at 6:54:48 PM UTC-4, wrote:
Using a Portable PowerFLARM the first time a few weeks ago I noticed that there were sometimes two targets for a given glider. When I first got near the glider and it showed up on the screen, it was a "hard" target on the built-in display. Once I was in the thermal, however, sometimes that hard target would be supplemented by a ghostly image near it. I was wondering if that was the previous target that the FLARM was trying and failing to verify without processing that the "new" target was the same one that had been displayed some seconds before.

Anyone had this happen? It wasn't a big deal at the time but I'm a little concerned it would/will be with 50 gliders around at Elmira.

Chip Bearden
ASW 24 "JB"
U.S.A.

It changes from a triangle, showing direction of flight, to a circle, showing it is thermalling. When it leaves, it goes back to a triangle showing direction of flight.

I don't look at it in a thermal; only when it gives a collision alert.

I'm late to the FLARM party and my observations were based on only one flight. But what I recall seeing was *in a thermal*, a new target would show up as the only other glider in the nearby sky joined. Then, a circle or two later, there would be two images (I believe they were identical in shape--circles--but I can't swear to it), the second one a much lighter color gray (the "ghost" image I referred to) was usually near but not exactly overlaid on the darker symbol (although I guess I wouldn't have been able to see if they were precisely on top of one another). The light gray symbol quickly faded away in a few seconds. The dark symbol behaved normally.

This happened repeatedly. Given the nearly empty sky that day and the number of times this occurred, the FLARM screen was obviously showing the same glider in two different positions and in two different colors. Was it a case of trying to refresh the screen and displaying where the glider was now and where it had been a few seconds earlier? Or was this cause by some sort of reflected signal? I have a canopy wire deflector cage in the cockpit and the range pattern I saw shows a large narrow loop of enhanced sensitivity way out to the left that caused me to wonder if part of my canopy wire deflector was acting as a parasitic antenna. Or was the fact that my flying buddy was transponder and FLARM equipped causing my FLARM to read him as two targets?

I just wanted to know if this was normal. My buddy hadn't seen anything like this on his display, but he didn't have a portable unit. This was a trial flight with few people flying so I gave the screen more attention than I otherwise plan to in the future. FWIW, I didn't see the same phenomenon for the fast-moving targets up high.

Chip Bearden
ASW 24 "JB"
U.S.A.

I never seen nor heard anything like that. My guess is that you may have a unit with bad display which is not getting refreshed fast enough.

Ramy

My previous experience with ghost images (PF Core + LX FlarmView) was when a gliders signal was lost. The combo would leave the traffic displayed for a set time period for general awareness. You could cycle to the target to see the CN but not get any altitude data. As it came back in range, the target filled in again and presented normally. As you were thermalling, perhaps you were experiencing a similar thing as the fuselage blocked your signal? I note your question refers to PF Portable thus YMMV.

CJ

Indeed the butterfly display will continue showing a target for few more seconds after the signal is lost, to prevent flickering and for awarness. This is a good thing. But it should not result in double targets. I never seen a double target in my brick butterfly display in the hundreds of hours I've been flying with powerflarm.

Ramy