Comm gear surviving an EMP, any ideas?

I've always been told that vacuum tube gear is far more resistant to EMP than anything transistorized. The R390A is a legendary receiver regardless, a mechanical engineering marvel with a noise floor close to the galactic level. But yeah, I heard they kept stockpiles of them til the 80s specifically because they were EMP resistant.

I only know the basics when it comes to encryption - it's best to have a radio with an ECM, which is hardware encryption as opposed to software. That's a rabbit hole, no doubt.

As far as evading RDF, it depends on the situation. Obviously, use the lowest power level possible, keep transmissions short, and when you're static, set up a hot loop/field phone so RDF becomes irrelevant. There's a whole aspect I know almost nothing about that you might be interested in - mesh networks, which are supposed to offer advantages of security over traditional RF simplex/repeaters.
 
The R390a is ten times the cost today than when new!! S working unit on eBay is about $1k! I know they are nice but hard to kit up a full MAG.

the problem I’m trying to get around is the repeater is located at the MAG hub. My thinking is to move it but it’s s big process. It’s location. Could be found easy using RDF.

I’m going to look into the mesh network.

What is a hot loop/field phone?