But the transponder type ones are pricey are they not? However, You get to see who what and where they are headed and they get to see if you are 5 10 or 15 points for the days game of Chicken. I am with IT in that AIS is the best for both parties. Active reflectors are supposed to detect a signal and then 'ping' the frequency back out, which is sort of the electronic version of waving your arms to say here I am. The idea that the shape also focuses the reflection is an old wives tale. The round shape that locks into itself means some kind of flat surface points in the general direction at some point. The idea of wrinkled foil came about due to the thought that some surface is going to be reflecting back in the right direction somewhere. But a certain amount of Radar does get bounced back OK. A mast is not the best of shapes and for that matter, neither is the a Boat hull. Not that the actual image is the issue, it's more about how much of that light gets bounced off in a different direction and misses the Radar receiver part. Any other shape will return some form of image by 'scattering' the light. A flat mirror will return the best image. The reflection is determined by the shape. Think of those funny shaped mirrors at the sideshows etc.

Plus wrinkled up won't be best choice anyway. Wrinkled up aluminium foil inside your mast.Inside an alumimium mast? Don't think that will solve a lot.

Active radar reflector