Bruce,

Thanks for the response. I'll have to study what you offered and digest
it for awhile.

The short description of what I'm up against is that I an installing new
electronics on a 1970 Chris Craft that I've spent the last four years
restoring. The boat is in Tampa, Florida and as soon as it hits the
water I will need to bring it home to the Caribbean where I live. I
will not have more than a few days time in Tampa where I have some
resources available before I take off. The shake down will be as I
cross the state to the east coast.

At this time the set up is Autopilot, VHF, Twinscope, GPS/Chartplotter,
and Radar at the lower helm. To the side, away from these will be the
SSB which I have not purchased yet. The VHF will also be operated from
the upper helm by way of a remote extension microphone. Both VHF and
SSB antennas will be mounted on opposite sides of the flybridge. This
is a separation of about eight feet. The radar antenna will be on a
mast above the upper helm and to the rear of the radio antennas by about
6 feet. I have just about convinced myself to install a second station
setup on the flybridge. If I use a second radar the antenna will have
to mount above the other one on the mast. I do not expect to use both
radars at the same time since I can't be at two places at once. And it
would require really extending the radar mast to separate them.

You said that you must eliminate noise at the source. My idea or
question was that if I put capacitors on each power feed to each
instrument, would this eliminate it as a potential source of trouble?

What do you consider to be a "good" alternator filter?

I have head differing opinions on positioning of the antenna tuner.
There is enclosed space under the bridge console and since this is near
where the antenna would mount I was thinking to mount it here. The
transceiver would be located on a shelf in the cabin within reach of the
lower helm. The boat has a built in counterpoise formed into the
fiberglass hull below the engines.

I'll have to figure out what size capacitors to use across the various
motors.

Thanks again for the response.

Earl

Typical solution is to shut down the inverter or charger
while using the radio.

I could do this but every time I switch the chargers back on they initially
go to bulk charge mode at 14.2 volts and I think they are programmed to hold
this for 30 minutes. I'm not sure this is doing my fully charged batteries
any good, especially if I want to listen to my SW radio every evening.
I'm hoping the twisted pair output wires do some good. If not I may have
some battery chargers for sale.

"Doug Dotson" wrote in message
...
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

Earl,

All marine equipment must at least meat IEC and FCC standards with regards
to unwanted emissions and susceptibility to RF emissions. On top of that,
most marine electronics manufacturers meet the IEC945 standard, which is
specifically designed for the marine environment and has, amongst others,
much lower limits on unwanted RF emissions on marine frequencies.

So to make a long story short: give each device a decent power pair and you
will have no trouble at all.
If you use screened wire for data connections (NMEA et. al), use a wire
within the cable for ground/return connections and connect the screen ONLY
ON ONE SIDE to ground. Do NOT use the screen as a return path for a signal.

When you need to use an inverter, feed that beast directly from the battery
and install filters on the input and output IF you experience problems. And
buy a decent (=expensive) one, not one of those cheap crap square wave or
modified square wave types.

As for the SSB: the only good place for the tuner is DIRECTLY at the feed
point of the antenna. If the SSB interferes with the other equipment, use
ferrite clamps on the wires to a device, as close as possible to that
device.

Meindert (marine electronics engineer).

On Thu, 05 Aug 2004 17:09:51 GMT, "Gordon Wedman"
wrote:
I could do this but every time I switch the chargers back on they initially
go to bulk charge mode at 14.2 volts and I think they are programmed to hold
this for 30 minutes. I'm not sure this is doing my fully charged batteries
any good

==================================================

It's not the charge voltage that's so important as much as the charge
current (this assumes conventional lead acid batteries). If your
batteries are already fully charged they should float up to 14.2 volts
very quickly and charge current will be quickly reduced. A proper 3
stage charger will sense the low charging rate and switch to float
mode.

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.

In article ,
"Doug Dotson" wrote:

Bruce,

Have you actually had problems as extreme as you are relating to
here or have you just been reading the catalogs and seeing
products that you feel will keep ypu out of trouble?

Noise filters I have heard of. Never heard them referred to as
power filters though. I've never had to resort to anything other than a
few ferrite beads to solve noise problems. Some minor comments
below.

Doug
s/v Callista

Oh yea, I have seen some real Doozies of RFI in the last 35 years that
defied the easy fixes that most folks use. Noise is ALWAYS easier to
stop at the source, than at the receiver. Inverters aren't to bad if
you get them installed with short battery leads, and they are designed
for the Marine Enviormewnt. Trace used to build some fairly quiet ones.
Radars have a very nasty habit of haviung the interconnect cable come
ungrounded one one end or the other and radiating noise at the PRR.
the Decca 101's were notorious for this. some of the Rartheon Marine
Radars run Chopped Dc up the interdeck cable, to power the transmitter
and if the cable ground opens, they radiate like crazy. Most of the
alaskan fishing fleet has Oil fired stoves in the galley that use DC
Blower Motors. These make a big racket when not suppressed with Caps.
Refer motors are the same game as well. If you really want a quiet
MF/HF boat, you got to pay the price in RFI Suppression.


Bruce in alaska

--
Bruce (semiretired powderman & exFCC Field Inspector for Southeastern Alaska)
add a 2 before @
Bruce Gordon * Debora Gordon R.N. Bruce's Trading Post
P.O. Box EXI Excursion Inlet South
Juneau, Alaska 99850 Excursion Inlet, Alaska 99850
www.btpost.net www.99850.net

In article ,
Earl Haase wrote:

You said that you must eliminate noise at the source. My idea or
question was that if I put capacitors on each power feed to each
instrument, would this eliminate it as a potential source of trouble?

What do you consider to be a "good" alternator filter?

You really only have to supress the noise if you actually have a
generator making it. I would install the equipment, and then move the
boat out, away from any yard or industrial like setting, before testing
for RFI. One of the things I have found over the years, is that most
shipyards are VERY NOISY PLACES, and you can't really find locally
generated noise, because it is being masked by the Yards noises.
Back in the day, we used to do most of the testing while the boat was
out on SeaTrials in Puget Sound, well away from the yards and docks.

Numar builds a very good set of Alternator Filters, that we have used
for years. I like their 80Amp version, myself, but the 160Amp version
works well for those BIG Alternators.


Bruce in alaska
--
add a 2 before @

I was referring to the project at hand. I know that there are tons
of potential noise problems but what about actual problems with
the installation under consideration? I can;t see sinking alot of time
anf money based upon worst-case scenarios.

Doug
s/v Callista

"Bruce Gordon" wrote in message
...
In article ,
"Doug Dotson" wrote:

Bruce,

Have you actually had problems as extreme as you are relating to
here or have you just been reading the catalogs and seeing
products that you feel will keep ypu out of trouble?

Noise filters I have heard of. Never heard them referred to as
power filters though. I've never had to resort to anything other than a
few ferrite beads to solve noise problems. Some minor comments
below.

Doug
s/v Callista

Oh yea, I have seen some real Doozies of RFI in the last 35 years that
defied the easy fixes that most folks use. Noise is ALWAYS easier to
stop at the source, than at the receiver. Inverters aren't to bad if
you get them installed with short battery leads, and they are designed
for the Marine Enviormewnt. Trace used to build some fairly quiet ones.
Radars have a very nasty habit of haviung the interconnect cable come
ungrounded one one end or the other and radiating noise at the PRR.
the Decca 101's were notorious for this. some of the Rartheon Marine
Radars run Chopped Dc up the interdeck cable, to power the transmitter
and if the cable ground opens, they radiate like crazy. Most of the
alaskan fishing fleet has Oil fired stoves in the galley that use DC
Blower Motors. These make a big racket when not suppressed with Caps.
Refer motors are the same game as well. If you really want a quiet
MF/HF boat, you got to pay the price in RFI Suppression.


Bruce in alaska

--
Bruce (semiretired powderman & exFCC Field Inspector for Southeastern
Alaska)
add a 2 before @
Bruce Gordon * Debora Gordon R.N. Bruce's Trading Post
P.O. Box EXI Excursion Inlet South
Juneau, Alaska 99850 Excursion Inlet, Alaska 99850
www.btpost.net www.99850.net

In article ,
"Doug Dotson" wrote:

I was referring to the project at hand.

It was not my project. I was replying to a previous Poster.


Bruce in alaska
--
add a 2 before @

"Terry Spragg" wrote in message
t.cable.rogers.com...
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.



So how does he reduce excessive atmospheric noise or out-of-band signals?

Ed
wb6wsn