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Old 03 March 2012, 07:47   #1
Country: UK - England
Town: Surrey
Boat name: Fugly & Rokraider 1
Make: Pac 22 & Porter 6.5
Length: 6m +
Engine: Ford 250 & jet,DT140
Join Date: Jun 2008
Posts: 681
Icom M505 - Garmin 450 wiring advice please

I am mounting a new Icom M505 dsc radio on my Rib and want to hook it into the newly overhauled Garmin 450 for the GPS function. I am finding the wiring rather confusing and would appreciate some advice before I do any damage getting it wrong.

The M505 handbook states that the NMEA IN lead (red coaxial type) connects to GPS receiver for position indication. It then states A NMEA 0183 ver 2.0 or 3.01 (sentence formatters RMC, CGA,GNS,GLL and VTG) compatible GPS receiver is required.

It also states that NMEA OUT lead (white coaxial type) connects to a PC or navigation equipment (NMEA 0183 ver 3.01 sentence formatters DSC, DSE compatible) for position data received from other ships.

The Garmin 450 installation instructions state that the 450 has NMEA 0183 and Garmin CANet.

I do not know what version NMEA 0183 the 450 has on it, It has just come back from Garmin after a overhaul (it looks to be a another new unit to be honest), so I am wondering whether it will have the latest version of NMEA 0183.

Am I right in thinking that the outer sheaths (-) on the NMEA leads coming in & out of the 505 need to connect to a common ground used by the 505 and the and the Garmin as well?

In the Garmin installation diagram, it shows it having 2 wires going to earth, the power ground and a NMEA ground. On the actual (new) wiring harness that has come back with the Garmin it has the colour codes on label attached to the harness.

The Garmin label colour codes are: The M505 schematic shows
Red - Power 1) Coaxial type Red (NMEA IN +)
Black - Ground Sheath -
White - Can high* 2) Coaxial type White (NMEA OUT +)
Green - Can low* Sheath -
Brown - P1RXD 3) Coaxial type yellow External speaker +
Blue - P1TXD Sheath -
Orange - ACC on 4) Hailer Foghorn Black -
Yellow - Alarm 5) Hailer Foghorn Blue +
Grey - P2TXD 6) Antenna
Violet - P2RXD 7) Ground Terminal
*CANet compatible unit only 8) External mic jack
9) DC power connector

I would appreciate some guidance on which wires to connect to what with regards to the DSC stuff.

i am also interested in wiring the loud hailer that I have on the RIB so that it can be used as a PA / Foghorn as well as an external loudspeaker for the radio. Is this possible ?

Thanks for any advice.

Rokraider is offline   Reply With Quote
Old 03 March 2012, 10:43   #2
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,653
At the GPS end, red to 12V, Blk to GND.

Radio NMEA IN+ to GPS NMEA OUT+ (blue)

Sounds to me that that's all you need, assuming both units are powered up. The shield on the radio NMEA connection may need to tie to ground, but probably not. You can connect the VHF NMEA Out to GPS NMEA IN, but you probably won't gain anything (most consumer GPS's won't display targets from NMEA data.)

You do need to match the speed and protocols for both units (baud rate, start and stop bits, and parity.)

jyasaki is offline   Reply With Quote

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