Interference - VHF and tach
Looking for ideas on how to limit electrical interference in two specific areas:
1) There is a VHF radio located about 4 feet from the 2000W inverter. When I key the mike, a loud 60Hz hum can be heard on the receiving end.
2) One of my tachs is fine at the dock, but underway will suddenly jump up to twice the actual RPMs whenever I get above about 1500 RPM. Tachs are fed off the alternators.
The first one is obviously interference, it goes away when I power off the inverter. Not sure where it's getting "in" to the radio though. Do I address the power supply wires, or try to shield elsewhere? And how?
The second one is not so obvious. I've ordered enough primary wire to replace the entire run from the alternators to the gauges. I'm wondering if I should have gone with coax instead.