Handsets crash??? Huh??? I am sorry but that is stretching things a bit.  The company that I work for is doing the rebanding of all the subscribers for the city and county.  All in total it's about 40000 radios.  So you are saying that something may infect these radios and cause all 40000 to crash? 

I think we are to a point in this discussion that people are grasping at straws to create some reason that ham radio and EMCOMM is beneficial.  First off, I never said it wasn't, at least not here.  I honestly don't believe it's beneficial in the manner that it's being portrayed, but in certain circumstances, and uses it is beneficial. When the discussion of needing to pass health and welfare during a hurricane between shelters, I get that.  When some clown starts talking about needing a ham to ride around in every police car and fire truck because all the public safety comms have failed, that's taking it a bit too far.   

As far as terrorists taking down a radio system.  I do know the specific vulnerabilities of them and while I will not specifically go into them here, I will say that it would be rather difficult to fully render a system completely inoperable with  this magical "jammer" that you speak of.  You have to understand how they actually work to know how they will react to interference.  It's not a single site, single freq repeater that you simply generate a carrier on its input and render it useless.  Nice try though. 

I am not sure why you say  a 50 Ohm Z for the antenna is  important. If there is a mismatch, what is the problem? Signal and noise will perhaps be less, but in equal measure- so the resultant signal to noise ratio is unchanged.

Dale W4OP