Sanderling's current radar is a Raytheon R40 raster scan radar that was
installed on the boat in 1990. Although it doesn't have a lot of bells
and whistles compared to a new model of any kind, it functioned
perfectly for us last summer in foggy Rhode Island Sound, Maine and the
Bay of Fundy - we couldn't have asked for a better display of our
surroundings, which even included lobster pot markers and birds in the
water at the 1/4 mile range when we couldn't see more than a hundred
yards - and I'm not interested in replacing the radar with a new one
that will provide only slightly more functionality.

However, I would like to take advantage of functionality that seems to
be built into the radar which could be awakened with NMEA data from our
GPS chart plotter. With NMEA data the radar can display position, SOG,
target and waypoint information (as well as some other NMEA-based info).
The display unit has a connection on the back of the display for a BNC
connection which the user's manual indicates is to accept NMEA data from
a Loran C and refers to NMEA 0183 with GLL, GTD, VTG and BWC sentences.
Specifically, the manual states:

"The R40 is programmed to accept data from the Loran in the NMEA 1082
and NMEA 1083 formats . . . The NMEA 1083 data standard will, in most
cases, provide Lat/Long, TD course and speed data for the radar display
. . .The connection to the R50 Display Unit is made with a common BNC
connector. RG 58 A/U Coax cable of any length may be used to complete
the interconnection to the Loran C. A two wire, shielded cable may be
used in place of the RG 58 coax if necessary. . . ."

Two questions come to mind:

(1) Is the  NMEA 1083 sentence format from a GPS now the same as it was
back in 1989 from a Loran C when this unit was made? (I realize the data
stream may contain more information now than it did in 1989, but are
GLL, GTD, VTG and BWC sentences now the same as they were back in 1989?)

(2) Can any decent-sized wiring be used other than shielded cable as
long as I can attach a BNC connector at the display unit end? (The NMEA
data from the GPS comes from an 18 or 20 guage wire, and I'd prefer to
just run a little heavier wire and end it with a BNC connector if that
were possible.)

I'd appreciate any thoughts you might have regarding this lash-up.

--
<><><><><><><><><><><><>Mozilla Thunderbird<><><><><><><><><><>
Bob McLeran and Judy Young                  Manatee Cove Marina
MV Sanderling                              Patrick Air Force Base
DeFever 41 Trawler                          Melbourne, Florida

Thursday, December 11, 2008, 4:33:55 PM, Bob wrote:

BM> "The R40 is programmed to accept data from the Loran in the NMEA 1082
BM> and NMEA 1083 formats . . . The NMEA 1083 data standard will, in most
BM> cases, provide Lat/Long, TD course and speed data for the radar display
BM> . . .The connection to the R50 Display Unit is made with a common BNC
BM> connector. RG 58 A/U Coax cable of any length may be used to complete
BM> the interconnection to the Loran C. A two wire, shielded cable may be
BM> used in place of the RG 58 coax if necessary. . . ."

That should be NMEA-0183, I expect.

BM> Two questions come to mind:

BM> (1) Is the  NMEA 1083 sentence format from a GPS now the same as it was
BM> back in 1989 from a Loran C when this unit was made? (I realize the data
BM> stream may contain more information now than it did in 1989, but are
BM> GLL, GTD, VTG and BWC sentences now the same as they were back in 1989?)

Yes - NMEA occasionally adds new sentences but I think most things
will still work.  If your GPS has a choice of NMEA versions, you may
need to use the earlier version.

BM> (2) Can any decent-sized wiring be used other than shielded cable as
BM> long as I can attach a BNC connector at the display unit end? (The NMEA
BM> data from the GPS comes from an 18 or 20 guage wire, and I'd prefer to
BM> just run a little heavier wire and end it with a BNC connector if that
BM> were possible.)

I usually use #22 wire, but any size should be fine - it is just a
signal, no significant current required. (I thing the wiring from my
Garmin GPS17 antenna/receiver is only #28).

BM> I'd appreciate any thoughts you might have regarding this lash-up.

--
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca