Using an Acom 2000A.connected to a 20m Yagi, When listening on the carrier on a portable receiver, attenuator on, short whip antenna, it sounds nice an clean. 2. harmonic on 10m has a lot of hum-modulation, I would guess more than 50 % . And it is wide and noisy. The hum is power line harmonics sounding really distorted. Any ideas ?