luc wrote in news:ecec55da-96b1-44a2-974a-86bb820f6e73
@e23g2000prf.googlegroups.com:

Hi folks,

I'm trying to get my Garmin 982 NMEA 183 to talk to my newly installed
Raymarine Pilot. There are two Garmin NMEA out wires, but one of them
is ground. Since the pilot 'brain' is already grounded, do I need to
attach the ground from the garmin to the ray pilot? The brain has two
terminals for "in" and two terminals for "out". Makes some kind of
sense that it should have two wires, but I don't understand the point
of ground since it's all a common ground, pilot, garmin, all goes to
battery negative.

any suggestions?

thanks

Luc

Which model number "Pilot" are you using so we can all be in the same
commissioning manual, together?

Because Garmin only uses the + NMEA wire for data, doesn't mean you don't
need to hook up the negative wire. The way Garmin grounds the NMEA -
only makes it transmit to your radios, so you should make the time to use
FOIL SHIELDED 2 or 4 wire cable WITHOUT hooking the shield to the NMEA -
connection at all. Don't just shove them under the NMEA - together. The
shield drain wire needs to be hooked to the data SOURCE DC ground point,
in this case the Garmin GPS as short as practical, ONLY. Clip the foil
and drain wire off the other end at the Pilot computer and hook it to
nothing. This is called a Faraday Shield, after Micheal Faraday to
invented capacitors long ago. Don't leave long wires hanging out of the
shield on either end as they will radiate. Notice in your manual that
Raymarine also wants you to use FERRITE ISOLATORS to absorb data going
down the wires, another good idea you can buy at any Radio Shack.

Now, the -NMEA data wire should be hooked to ground on the Garmin end and
ONLY NMEA - on the Raymarine end...not grounded there. Trying to bypass
this wire will introduce noise from ground loops if you try to use the
boat's common ground instead of an actual wire....adding confusing pulses
to the data system no instrument will like. Dealing with data is lots
different than dealing with DC powering lights. Noise is important...in
and out.

If your "new Pilot" is one of the S types, the Garmin should be hooked
into the COMPUTER NMEA IN port....not the display NMEA in port at the
helm. The manual I read says it reads the computer port for data FIRST
and the display port SECOND. GPS data goes in the computer port
according to the manual. If you have other NMEA talkers, the second port
on the helm display NMEA IN allows you to simultaneously connect their
data outputs there, such as a wind instrument sending wind data so the
PILOT will operate in wind vane mode, following the wind at night,
instead of a course, easing the darkness crew from resetting sails.
Without wind data, windvane mode cannot work.

AND NO WIRES ANYWHERE NEAR THE FLUXGATE to drag the compass off when
someone switches something on! I just got through fighting that on a
sloop noone seemed to be able to figure out. The damned wires to the
BILGE PUMP were causing 15 degree errors every time the bilge pump
cycled, creating some hilarious looking compass courses...(c; I found it
by sailing across the harbor on the fluxgate data and turning things on
and off. Noone had hung down in his deep bilge and pulled up the FLOAT
SWITCH QUICKY JIBE AND PANIC THE CAPTAIN DEVICE....(c; The wire was on
the other side of a bulkhead from the fluxgate....only the + wire. 5A
sure pulls hard on a compass fluxgate...(c; Whirrrr...and away we went!


Larry
--
Next time some broker tells you what a great investment he's selling,
ask him about Rhodium, a shiny metal used in Catalytic Converters.
Jan 1st 2004 2005 2006 2007 2008
Rhodium $452 $1341 $3006 $5339 $6775 PER OUNCE!
How much longer can we pay for new cars at this rate?
Feb '97 it was $182/oz