I ran a dedicated voltage wire between MTUs. I bought one set of filters, installed them at one panel, then ran a 'filtered' voltage to my second MTU. I actually installed a new circuit breaker at the panel nearest my internet router, powererd a new outlet with the filtered voltage, and plugged my gateway into that. From that new outlet, I picked the 'filtered' voltage. This creates a small error, because I seem to have some small voltage drop across the long wire. I can live with that. For your situation, it might be worse because of the distance. But, short of installing two gateways - which is a different problem - I couldn't figure out a better way. My system works great, other than the very slight differences in voltage readings.