I had a newly installed transponder start leaking smoke & stink in the cabin one time. I used the off switch. In the mid to late 1970's, ATC discovered they could filter out the weather and most all of the traffic that they were seeing on their screens by turning down the gain on their primary radars and dealing only with the transponder returns. Separation of IFR traffic is their concern. The pilots now deals with non transponder equipped traffic and weather conditions. Before that time the ATC folks were very good at helping with weather avoidance and vfr traffic. I am very skeptical about any claims that there is more traffic now than used to be. General aviation appears way down to me. There used to be a proximity warning device manufactured by Genave (I think) that received and indicated the general direction of transponder returns from nearby aircraft. It was unfortunate enough to come to market at a time when the Fed's were mandating ELT's, encoding altimeters and new transponders for every one. John Ferrell http://DixieNC.US ----- Original Message ----- From: "Mike Hord" To: Sent: Thursday, June 17, 2004 5:17 PM Subject: [OT:] Aircraft transponders > One of the things that I'm hearing in NPR coverage of the > 9/11 commision's findings is that the aircraft in question were > lost because the hijackers turned off the transponders. > > I'm now certain that any question I can ask can be answered > by someone on the PICLIST, so I'll ask this now: > > Why on Earth is there an off switch on the transponder? > What could EVER make turning the transponder off a good > idea? > > Side point: how difficult would it be to set up several > antennas to pick up aircraft transponders, triangulate their > position, and project that info onto a map? I think it would > be fun to monitor local air traffic. Is this even legal? I know > that's the kind of thing that may not go over well these days. > > Mike H. > > _________________________________________________________________ > Is your PC infected? Get a FREE online computer virus scan from McAfee. > Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963 > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.