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?