On Saturday, April 19, 2014 2:49:22 PM UTC-7, wrote:
It would be nice to have the option to include a list of transponder codes that were always suppressed. For example, 1202. One could make the determination if a majority of the local gliders with a transponder also had FLARM. If that was a reasonable assessment for your location, then suppressing all the 1202 hits would potentially reduce the false alarms based on transponders and would rely on the more reliable FLARM data.

Ah the trouble there is you cannot definitively associate a Mode A squawk reply with the same transponder doing a Mode C reply. And there will be situations where targets are doing Mode C only replies (e.g. any time a target is being interrogated by TCAS I or II but out of range of ground SSR... which I'm guessing happens a fair amount).

The 'best' you could do in that situation is stop all PCAS warnings. That may be/is likely too drastic, you can also so try adjusting the PCAS height/range parameters. Ultimately there is nothing you can do that is goign to work that well with Mode C transponders. Hopefully over time this will go away as an issue as Mode S transponder use keeps growing in the USA glider fleet.

There is no need/strong justification to replace a Mode C today, they work great for letting ATC know where you are and with TCAS, TCAD and PCAS in GA aircraft etc. but on the other hand there is no sane reason to buy a new Mode C transponder today. The possible issues here with PowerFLARM interoperability is just one of those reasons. Over time and as equipment ages and gets expensive to repair and new Mode S transponder technology hopefully keeps falling in cost and size etc. we'll just see the current Mode C usage in the glider fleet migrating over to Mode S. I'm much less worried about Mode C vs. Mode S than I am to encourage *any* transponder use in areas of high airline, fast jet, and even GA traffic.

Anybody who what my opinion on what the FAA should have really done with Mode S vs. Mode C transponders and ADS-B Out carriage mandates, etc. is welcome to buy me a six pack of beer and put up with an hour of whining.