Is it legal to fly without a radio in Germany?
paragraph 3 clearly states that the only exception to the requirement to carry a radio set is when you're not leaving the immediate vicinity of the airfield, and then only when there's no ATC coverage.
That effectively means you can fly a few circuits at low altitude over a small field, but even then many of those would be close enough to a larger airport that has ATC coverage that they'd be covered by that airport's ATC system rather than having their own.

The only "loophole" would be if you could convince authorities that your flight wasn't planned, good luck with that.
Effectively that'd most likely mean you're having to prove to them that you went to the airfield without wanting to fly, just jumped into an aircraft, took off, and started zooming around the sky. Something that's so far out there nobody's going to buy it.