Bruce in Alaska wrote:
In article ,
Earl Haase wrote:


Bruce,
In the past you have posted here about all your experience in
electronics repair. I am confident that you knew what I was asking.
After all, I just asked a couple of questions in order to get the
opinion of others who would hopefully share their collective knowledge.
I don't know why this ****ed you off so much but if you don't want to
play nice please feel free not to play at all.

Earl



I am not '****ed Off" at all, I just want a clarifacation on what you
are trying to do. We get all kinds, asking for advice, and most can't
detail what they really want, let alone ask intelligent questions, about
subjects they are just learning about.

Now, first off, you NEVER eliminate noise at the receiver, but ALWAYS
eliminate it at the SOURCE. Filtering the power leads of marine
equipment, is only effective, IF that is where the noise is being
radiated FROM. ie Get a GOOD filter on your Alternator Output,
to keep it from using the DC Power System as a Radiating Antenna,
to the rest of the boat and all the folks in the same harbour.
Put a Cap ACROSS all the Brushed DC Motors, onboard wheather they are
noisy now or not, and do it as close to the motor as possible, and NOT
from each lead to the motor case. Most GOOD marine electronics has a
"Ground Lug" on the case. Use them, to connect each case to a common
LOW IMPEDANCE Grounding Point for electronics. If you have a "Plastic
Boat", build a common LOW IMPEDANCE Grounding Point for electronics,
before you do anything else. For SSB Radios, move the Antenna Tuner
as close to the RF Ground as possible, and keep it as far from the rest
of the electronics as practicable. Radars need to have their cases
connected to the common LOW IMPEDANCE Grounding Point, and make VERY
sure that you keep the Grounding Shield of the Interconnection Cable
between the display and antenna good and tight on BOTH ends. Put Caps
ACROSS the drive motor of your AutoPilot, and the Switching Relay
Contacts if your pilot has them. If you have multiple VHF Radio's,
make sure that the antennas are seperated by 3 or 4 wavelengths, both
vertically and horozontally, so as to eliminate direct coupling between
the radio's. If you have multiple MF/HF Radio's, design and build a
complete PTT/Antenna Break Interswitch system between the radios. If you
support multiple RADARS on the same Band, seperate them vertically, so
as to keep their 25 degree vertical beamwidth antennas from seeing each
other. Mount Inmarsat Antennas way from GPS Antennas, as they use the
same bands.


Bruce in alaska who gives away $1000US advice, for free, to
those who ask

The above prompts for one of the two following replies:

1. I don't know.

2. How can I get the 1000 bucks in cash?

;-)

So far, no one has answered the twisted wire part of the question.

DC wiring passing close by magnetic compasses should be twisted
tightly to eliminate induced deviations in the compass when the
circuit is in use. Metal instrument panels should never be used for
electrical connections, except possibly for shield earthing. Metal
instrument panels might best be of Mu metal, a magnetic shield.
Ferrous, or other magnetic materials should be avoided. Copper,
aluminum or brass is also good.

There is no other reason to twist wiring generally beyond reduction
of picked up noise in circuits feeding high gain input circuits such
as microphone inputs, analog current sense lines, etc.

All electric devices should have their own separate power return
"ground" lead all the way back to the source. If a device is
causing noise, a capacitor across the wires at the device end can
help eliminate the noise. Of course, devices that generate noise
should not be selected for use anyway. In addition, ferrite beads in
both wires before and after the capacitor will also help.

Proper noise filters consist of a choke coil of sufficient current
capacity, possibly toroidal in design, in series with the wire
filtered, or both + and - leads, with capacitor networks across both
leads and chokes, possibly professionally tuned to specific
applications and bandwidths. Light dimmers for AC lamps, and
fluorescent tube fixtures come to mind.

Specific advice in difficult scenarios can be expensive, as Bruce notes.

Terry K -30 years experience as a military radio electronics tech.