I have a problem that's got me stumped. I am getting NMEA string noise in my
SSB on various channels, starting with 2162.

I have a Garmin GPS that feeds into a Noland Engineering NMEA Expander. The
SSB and three other devices come out. When I turn the power off to the
expander, I lose my GPS signal to all of the devices. When I power it up, I
get the noise in the SSB.

I even hooked the SSB NMEA cable to the input side of the expander, directly
to the GPS signal, and I still get the noise when the expander is turned on.
Thinking the expander was bad, I contacted them, and they sent a new one.
Same problem. I even get the noise in the SSB when the NMEA data cable is
unplugged from it. It has to be coming in either radiated or through the
power supply.

I'm lost... any suggestions?

Keith, you need to do some more snooping to try to isolate where the "noise"
is coming from, and how the RFI is getting into the set! You are on the
right track so far.......

FIRST, with the noise present on the SSB,. turn off ONE NEMA device at the
time to try to see if one of them (above all others and, of course, the
expander) is THE culprit. Is the expander taking ship's DC from the same
power bus as the SSB? Are they physically close if on the breaker panel?

With the NEMA unplugged from the SSB, remove the antenna cable from the back
of the SSB...is the noise still there? Would it be easy to power up the SSB
with a separate power source away from ship's DC....another battery
perhaps....with it's power leads run clear of the NEMA devices?

Looks like you may have to add some ferrites to the various NEMA cables,
your power cables....or shield the device in question.

Take note of what makes the noise lessen or go away completely.

Post your answers here and the experts will take over.....

Good luck.....Joe


"Keith" wrote in message
...
I have a problem that's got me stumped. I am getting NMEA string noise in
my
SSB on various channels, starting with 2162.

I have a Garmin GPS that feeds into a Noland Engineering NMEA Expander.
The
SSB and three other devices come out. When I turn the power off to the
expander, I lose my GPS signal to all of the devices. When I power it up,
I
get the noise in the SSB.

I even hooked the SSB NMEA cable to the input side of the expander,
directly
to the GPS signal, and I still get the noise when the expander is turned
on.
Thinking the expander was bad, I contacted them, and they sent a new one.
Same problem. I even get the noise in the SSB when the NMEA data cable is
unplugged from it. It has to be coming in either radiated or through the
power supply.

I'm lost... any suggestions?

It gets stranger. I did unhook each device from the expander one at a time,
and nothing made any difference. Of course, turning the GPS off or
disconnecting the power to the NMEA expander made the noise stop. Now get
this: I was hooking up the power to the NMEA expander, and I connected JUST
the positive lead, and it started transmitting the data, still with the
noise of course. NO ground hooked up at all to the "supply" side. One of the
four devices hooked up is somehow supplying a ground of it's own.

The four items a
Raymarine Radar
Standard Horizon VHF
ICOM 802 SSB
Computer running Nobeltec VNS

????????????

Well, I finally took out the expander and hooked up a terminal strip with
the NMEA data coming in and hooked up to all four items NMEA IN wires, and
their four (-) wired jumped together, but not hooked to ship's ground at the
terminal strip, and it works fine, drives all four items, and no noise any
longer.

Things that make you go HMmmmmmmmmmmm...

"JAD" wrote in message
...
Keith, you need to do some more snooping to try to isolate where the
"noise"
is coming from, and how the RFI is getting into the set! You are on the
right track so far.......

FIRST, with the noise present on the SSB,. turn off ONE NEMA device at the
time to try to see if one of them (above all others and, of course, the
expander) is THE culprit. Is the expander taking ship's DC from the same
power bus as the SSB? Are they physically close if on the breaker panel?

With the NEMA unplugged from the SSB, remove the antenna cable from the
back
of the SSB...is the noise still there? Would it be easy to power up the
SSB
with a separate power source away from ship's DC....another battery
perhaps....with it's power leads run clear of the NEMA devices?

Looks like you may have to add some ferrites to the various NEMA cables,
your power cables....or shield the device in question.

Take note of what makes the noise lessen or go away completely.

Post your answers here and the experts will take over.....

Good luck.....Joe


"Keith" wrote in message
...
I have a problem that's got me stumped. I am getting NMEA string noise
in
my
SSB on various channels, starting with 2162.

I have a Garmin GPS that feeds into a Noland Engineering NMEA Expander.
The
SSB and three other devices come out. When I turn the power off to the
expander, I lose my GPS signal to all of the devices. When I power it
up,
I
get the noise in the SSB.

I even hooked the SSB NMEA cable to the input side of the expander,
directly
to the GPS signal, and I still get the noise when the expander is turned
on.
Thinking the expander was bad, I contacted them, and they sent a new
one.
Same problem. I even get the noise in the SSB when the NMEA data cable
is
unplugged from it. It has to be coming in either radiated or through the
power supply.

I'm lost... any suggestions?

"Keith" wrote in message
...
It gets stranger. I did unhook each device from the expander one at a
time,
and nothing made any difference. Of course, turning the GPS off or
disconnecting the power to the NMEA expander made the noise stop. Now get
this: I was hooking up the power to the NMEA expander, and I connected
JUST
the positive lead, and it started transmitting the data, still with the
noise of course. NO ground hooked up at all to the "supply" side. One of
the
four devices hooked up is somehow supplying a ground of it's own.

The four items a
Raymarine Radar
Standard Horizon VHF
ICOM 802 SSB
Computer running Nobeltec VNS

Check the connections on being differential or single ended. I'll explain:
A single ended connection has one signal lead and a ground. A differentional
connection has two signal leads, often marked A and B or + and -.
Oficially, NMEA is differential and with isolated inputs. Many manufacturers
however, abandon the standard and go the cheap way. There are two situations
that require a different wiring:

1. Single ended out to differential in
2. Differential out to single ended in.

1. Single ended out to differential in: this is the easiest to understand.
Connect the output lead of the talker device to "In A" on the expander and
connect the ground of the talker to "In B".

Many GPS's are single ended and are to be wired this way. Some have TX+ or
TX A and TX- or TX B, which can be connected to In A and In B.

The trick part is 2) Differential out to single ended in.
In this case, you connect Out A from the expander to the In lead of the
listener and you leave Out B open!. The ground from the listener has to be
connected to the ground of the expander.

Since you mention that there is a hidden ground path, it might just be that
one of the connected listeners is single ended in and you connected Out A to
the input and Out B to the ground of the listener. This will create a ground
path and a very heavy interference on SSB.

Maybe you could post the labelling of the inputs of the equipment you have
connected to the expander and how they are connected to the expander
outputs.

Regards,
Meindert

Keith, looks like you've got it licked! Like Meindert said....a hidden
ground loop. Pretty common....

You got off easy......sometimes these things are tough to track down.

fair winds......Joe
"Keith" wrote in message
...
It gets stranger. I did unhook each device from the expander one at a
time,
and nothing made any difference. Of course, turning the GPS off or
disconnecting the power to the NMEA expander made the noise stop. Now get
this: I was hooking up the power to the NMEA expander, and I connected
JUST
the positive lead, and it started transmitting the data, still with the
noise of course. NO ground hooked up at all to the "supply" side. One of
the
four devices hooked up is somehow supplying a ground of it's own.

The four items a
Raymarine Radar
Standard Horizon VHF
ICOM 802 SSB
Computer running Nobeltec VNS

????????????

Well, I finally took out the expander and hooked up a terminal strip with
the NMEA data coming in and hooked up to all four items NMEA IN wires, and
their four (-) wired jumped together, but not hooked to ship's ground at
the
terminal strip, and it works fine, drives all four items, and no noise any
longer.

Things that make you go HMmmmmmmmmmmm...

"JAD" wrote in message
...
Keith, you need to do some more snooping to try to isolate where the
"noise"
is coming from, and how the RFI is getting into the set! You are on
the
right track so far.......

FIRST, with the noise present on the SSB,. turn off ONE NEMA device at
the
time to try to see if one of them (above all others and, of course, the
expander) is THE culprit. Is the expander taking ship's DC from the
same
power bus as the SSB? Are they physically close if on the breaker
panel?

With the NEMA unplugged from the SSB, remove the antenna cable from the
back
of the SSB...is the noise still there? Would it be easy to power up the
SSB
with a separate power source away from ship's DC....another battery
perhaps....with it's power leads run clear of the NEMA devices?

Looks like you may have to add some ferrites to the various NEMA cables,
your power cables....or shield the device in question.

Take note of what makes the noise lessen or go away completely.

Post your answers here and the experts will take over.....

Good luck.....Joe


"Keith" wrote in message
...
I have a problem that's got me stumped. I am getting NMEA string noise
in
my
SSB on various channels, starting with 2162.

I have a Garmin GPS that feeds into a Noland Engineering NMEA
Expander.
The
SSB and three other devices come out. When I turn the power off to the
expander, I lose my GPS signal to all of the devices. When I power it
up,
I
get the noise in the SSB.

I even hooked the SSB NMEA cable to the input side of the expander,
directly
to the GPS signal, and I still get the noise when the expander is
turned
on.
Thinking the expander was bad, I contacted them, and they sent a new
one.
Same problem. I even get the noise in the SSB when the NMEA data cable
is
unplugged from it. It has to be coming in either radiated or through
the
power supply.

I'm lost... any suggestions?

I too have the UNSHIELDED Noland Engineering broadband transmitter
aboard "Lionheart". Every cable on the boat's extensive system is
foil shielded twisted pair carefully bonded to a common point. But,
alas, what a noisy mess......Stupid NMEA is useless.

I'm going to put my Noland into a aluminum Budbox with each cable, and
there are many, being bonded to the box where the wire goes into it.
That should shut it up from radiating itself so bad, and it IS bad.

Our other problems with NMEA is the stupid MANUFACTURERS all drifting
off in their own directions, the idiots! NMEA was designed as a
BALANCED LINE standard.....when one wire went positive, the other went
negative, cancelling out any signal intrusion coming in and cancelling
out any radiation going out. Notice NMEA has a + and - wire, NOT + and
GROUND. If everyone used balanced isolators in and out, this would be
fantastic. But, we're BOAT electronics manufacturers trying to outdo
TV manufacturers trying to see who can make the cheapest piece of crap
that floats. Isolators and balanced lines costs pennies per unit more
to produce....what a waste of company profits. Let's just hook the B
(-) lead to CHASSIS GROUND making a hundred ground loops and ground
antennas feeding the SSB RF energy INSIDE the shielded wire. We're a
GPS company. Who cares about RF intrusion, anyways?! We're after
PROFITS with minimal parts counts. Single ended is always cheaper.

So, what happens aboard "Lionheart" is the idiots at Icom used a BNC
connector....AN UNBALANCED BNC ANTENNA JACK to hook coax cable
to....for its GMDSS "GPS Input" from my NMEA system. Right at the
TRANSMITTER I have a huge ground loop attached to the antenna tuner!
Stupid, stupid, stupid.

Then, the idiots at Garmin, geniuses one and all, use all unbalanced,
DC-grounded NMEA single wire I/O grounding the NMEA B (-) points to
ANOTHER DC ground point on the boat with lots of unshielded wire so it
radiates like hell into the HF rig and the HF transmitters 150 Watt
beast just scrambles any data on those wires.

Then, the idiots at Noland Engineering, not the brightest bulbs in the
box, tell me if I want output from the NMEA multiplexer to use WITHOUT
using the computer, I'm gonna have to hook the NMEA A (+) to the
COMPUTER'S RS-232C TX terminal.....not the NMEA TLK balanced output
leads which only run from the computer's RX terminal when the computer
(and The Cap'n) are running. Again, another UNbalanced output feeding
every NMEA input jack on every instrument on the boat....with another
DC ground antenna feeding RF into the shielding by the back door.

The list goes on and on. NOONE ever takes into account this crap will
be working in an RF HOT ENVIRONMENT out there! Every time you key the
transmitter, data ceases to exist and it will all go berserk until you
unkey that transmitter.....

How stupid.....Seatalk - Unbalanced, unshielded.....FastNet -
unbalanced, mostly unshielded.....

They all need to get together and have ONE STANDARD THAT'S BALANCED
AND TOTALLY SHIELDED and ridgidly enforced throughout the stupid
industry!

Don't hold your breath, every boat I work on has the same
troubles.......idiots.



On Sat, 20 Sep 2003 10:11:16 -0500, "Keith"
wrote:

I have a problem that's got me stumped. I am getting NMEA string noise in my
SSB on various channels, starting with 2162.

I have a Garmin GPS that feeds into a Noland Engineering NMEA Expander. The
SSB and three other devices come out. When I turn the power off to the
expander, I lose my GPS signal to all of the devices. When I power it up, I
get the noise in the SSB.

I even hooked the SSB NMEA cable to the input side of the expander, directly
to the GPS signal, and I still get the noise when the expander is turned on.
Thinking the expander was bad, I contacted them, and they sent a new one.
Same problem. I even get the noise in the SSB when the NMEA data cable is
unplugged from it. It has to be coming in either radiated or through the
power supply.

I'm lost... any suggestions?




Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?

On Sat, 20 Sep 2003 14:40:37 -0500, "Keith"
wrote:


Well, I finally took out the expander and hooked up a terminal strip with
the NMEA data coming in and hooked up to all four items NMEA IN wires, and
their four (-) wired jumped together, but not hooked to ship's ground at the
terminal strip, and it works fine, drives all four items, and no noise any
longer.

Things that make you go HMmmmmmmmmmmm...

NMEA will not tolerate, and is too stupid to handle, more than ONE
talker on a circuit. That's the whole reason you needed a
multiplexer. If there are 4 talkers, all talking at once because they
are all too stupid to LISTEN to the circuit before sending data (like
SeaTalk does for instance) the output data stream is a useless
addition voltage with no data on it. That's the multiplexer's job.
Hooking two NMEA outputs together can also damage the NMEA talker
circuits because one device is pulling the line low when the other
device is pulling it high, resulting in a BIG current through both
devices....not good!



Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?

Amen brother, amen.
73
Charlie
KS4VB