just want to put this out there...
because radar and IFF are so closely associated, i think there might be room for confusion
perhaps i am misunderstanding, but it sounds like there is the idea when an a/c is interrogated, that interrogation should appear on the TEWS - that is not the case
IFF is a separate system and there is a cockpit indication when your aircraft responds to an interrogation - and there is also a cockpit indication if an interrogation is received and your system was unable to give a positive response (that would be a good thing to know - would it not?)
so.. TEWS will only report *radars* (even then, only when they meet prescribed specifications - it is *definitely* not a perfect system - and let me tell you, that fact is most certainly exploited) and IFF, while it operates through and in conjunction with the radar, is a separate system and displays information on the VSD as well as other cockpit displays