Re: digital modes on 2m 70cm
Interesting point on the military aircraft , popular rumer had/has it , that one of the local police , out on traffic speed duty , close to a scottish air base , out of curiosity , pointed his hand held 'speed gun' at one of the aircraft coming into land , which lit up the counter measures suite , end of career ..
Its more to re-radiation , most of the aircraft to day are composite hulls , [one of the reasons for the 11 meter ww2 radar , was aircraft wing was round 35 feet , so it gave a good return signal] so the signals are not as good as in the past , polarisation , probably Horizontal , I would expect the return signal to be modified , dopper plays a part as well , so the decoder needs to have a wide acceptance
bandwidth , I think the doppler shift is up to x2 if the target is advancing , first shift tx> a/c then a/c >> rx , at 600 mph , that's round +150 Hz on 2 meter's ?
Ive found this write up by two spanish stations using a plotting/ prediction software package to give the expected angles / range , google translate makes a good job of converting to english , just noticed it was back in 2014 , when the decoder was re-worked during the eme testing
This was a scatter spot , from a French 10 watt 70 cm beacon, using a halo round Ae to south of france to paris 704 Kmt , confirmed by
19:56 432418 F5ZAS de F1RJ Op05 -19 dB F:2% in JN18AT 1390,6 Hz