On Wednesday, September 27, 2017 at 11:55:43 AM UTC-7, John Carlyle wrote:
I've been in 3 close calls with big iron while flying my glider inside the mode C veils N of PHL and also W of EWR. In all 3 cases I'm convinced that my Trig TT21 was a lifesaver. All occurred at about 6,000 MSL.

There were several things that were impressed on me as a result of these encounters. First, it is absolutely amazing how quickly these aircraft close on you from the time you first see them. Second, being 500 feet under a 747 or 737 in a glider is absolutely terrifying! Third, it was very difficult for me as a private pilot to dig out the needed SID or STAR information from paper charts - the advent of the geo-referenced SkyVector charts is a real step forward.

Finally, don't count on having 500 feet separation. The legal variance on altitude encoders is +/- 125 feet, so you might be as close as 250 feet!

-John, Q3

In three occasions I've been close enough to a SW 737 to do a passenger count. Once probably close enough to pick them out of a lineup. Is that 500'? Closer? Hard to judge. All of these were on the north side of Reno. Since installing a transponder, nothing anywhere near that close - plenty of 737 vectored around me though, confirmed by listening to Norcal Approach. Transponders and ATC do work, if you give them a chance.