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Old 08-28-2017, 08:47 AM   #17
diver dave
City: Fairport, NY and Palm Coast, FL
Country: United States
Join Date: Jan 2017
Posts: 1,785
Originally Posted by WesK View Post
If the interference is when the unit is operating as a charger (connected to shore power), we can forget about all the "modified sine wave stuff".

Battery chargers are notorious for creating RF interference but it's rare to transmit on a VHF radio when plugged into shore power and charging the batteries.

RF Interference can be transmitted two ways, through the air like a small radio station or through the AC or DC power system. If it's being transmitted through the air, it might interfere with receiving devices like your VHF reception or AN/FM reception but your VHF won't retransmit it.

So - if everything you have posted is accurate, the interference is being carried on your DC power circuit and is entering the VHF through the power leads and is being retransmitted by the VHF.

So - You need to filter the DC leads as close to the charger as possible. You need to keep everything but DC voltage off the leads. A capacitor across the leads is a pretty basic filter and will short the interference from one lead to the other. This may solve your problem or you may need a more sophisticated filter with one or more capacitors and an inductor.

I suggest going to a place that installs high end car stereos and talking to them about filters. Keep in mind that this filter must pass 40 amps or more of DC current so a small, cheap filter may burn out.

BTW: One of the best ways for someone who doesn't want to buy expensive equipment to trace RF interference is to buy an "old time" hand held transistor radio. Tune it between stations and move it around until the static increases dramatically. That's where the RF is coming from.
agreed. And, I have a 1963 Zenith pocket AM radio for jobs like this.
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