Are you living in that house in the room right behind those antennas? If you are well that vinyl siding, fiberglass insulation, and drywall that make up the wall will not block any of the 400MHz signal that's spilling over from those antennas when they transmit. Also there are 2 of them pointing in different directions, meaning it's also acting as a relay point or 'hop through' to another system. So you now have not one but 2 of them transmitting, plus the other systems, that it's antennas are pointed at, will likely have the same directional antennas beaming their signal directly at your location. So you're getting hit from multiple transmitters.
20 u tesla is natural background noise... but 200 u's is something man made.. and the fact you see it on and off really suggests it is coming from the RTU, because this is just how they operate, sending data in bursts every so often... they do not transmit all of the time.