You mean encounters that will be x10 times stronger than "hard encounter" for one person and x100 times stronger for 10, because this one person will call 9 his friends with radio, so it'll be equal if he'll find it alone and call his friends, this way they will have fair fight?
Like: I'm poor wastelander, alone, oh noes! An encounter!
You encounter: "An army of 50 evil raiders with fn fal HPFA's"
Or just remove this silly encounter multiplier for number of players, because you made radio to avoid it, what reason.
Yes, if radio reinforcements remain there will have to be a way for the NPCs to call in their own reinforcements to maintain comparable numbers. Eventually some encounters will be hard because they'll just get boosts until they are.
And afterall, isn't it just contradiction to promise of making low-tech stuff more useful, when there are weapons of this kind?
Not really. You can have useful low tech weapons whilst still having better higher tech. Of course prices are all over the place at the moment, so in that regards its not really a fair comparison yet. Expect prices to be squeezed closer together.