Inverters and switch mode charges can emit alot of noise. But you are
correct that the noise is not sent back up the supply lines. Alot of the
noise enters the VHF or HF radios via the antenna or unshielded portions
of the internals. Typical solution is to shut down the inverter or charger
while using the radio. Alot cheaper than spending alot of money on
fancy filters that only reduce the problem rather than solving it.

Doug
s/v Callista

"Gordon Wedman" wrote in message
news:vG7Qc.30972$hw6.24936@edtnps84...
Question 2. When and where should I use twisted pairs and why not just
twist everything, everywhere?

My hi-tech Xantrex / Statpower battery chargers produce terrible amounts
on
noise on my shortwave radios. I've been told that twisted pairs from the
outputs to the batteries may reduce this. Not got up the engergy to do
the
re-wiring yet. By the way, this noise is radiated rather than transmitted
down the wire with the DC.

Using twisted pairs for wire carrying clean DC, e.g. from batteries only,
is
just extra work for no benefit. I suppose some electronics might feed
noise
back up the DC line but I would think this unlikely in newer
equipment.......but maybe not battery chargers?

"Earl Haase" wrote in message
...
I am about to start a major rewire on the boat. Which brings up some
ideas and questions.

Idea/question 1. I have seen those expensive power filters for boating
electronics. Why can't I just build a dedicated power buss and drop
some capacitors across the power feeds to each instrument? As in going
back to when we had to build our own power supplies for computer floppy
drives.

The electronics I will be trying to protect are ...
VHF
GPS/Chartplotter combo
Scanning sonar (Interphase)
Radar
SSB
Autopilot

And I may put a second radar and/or scanning sonar at the upper helm.

Question 2. When and where should I use twisted pairs and why not just
twist everything, everywhere?

Earl Haase