Low RFI noise on ham radio 20m HF band during power outage.

20 meter band during brief regional power outage. Noise goes up by at least 9 db (probably 12 - 15 dB) when power is restored. Resonant dipole at 20 feet. No preamp or attenuator. No RFI inside the house, it's all from the neighbors. Location is densely built suburbia.