I realize this is a long shot, but does anyone have experience with the
Raytheon NMEA/SeaTalk bridge? I have an older one (4 years) that I'd
never used until recently when I bought a new Icom 502 and then I wired
in the bridge into my SeaTalk bus to transmit lat/lon info to the new
radio. When I first fire up the Autohelm GPS and the radio, it gets the
signal and the radio reads out the correct info, but after about 5
minutes of operation the radio data starts flashing and pretty soon it
reads "no data available." Because the bridge is solid state it's hard
to imagine that it works for a few minutes and then fails -- is this
possible? The bridge is wired into the bus in parallel with my
autopilot, and everything else on the bus is working perfectly. I want
to be sure the bridge is defective before I spend the $$$ to buy another
one; if it weren't for having to hook up another external antenna, it
would be cheaper to buy an inexpensive Garmin than to buy another bridge.

Jim

Stewart Vane-tempest wrote:

I have had a similar issue.

Setup is ST50 instruments, MLR GPS, ST2000 tiller pilot and DSC Radio.
INterestingly, it was my ST50 NAV repeater that gave no data errors. I
traced this to having the tillerpilot connected to the seatalk interface but
not powered on!

I wired the multiplexor in series with the existing seatalk network and then
took the NMEA output to the radio and the input from the GPS.

It might be worth checking which version NMEA you have set up as the
standard ( I forget the versions, but there are at least 2 out there!)

Hope this helps somewhat.

Regards,

Stewart

"Captino" wrote in message
...
I realize this is a long shot, but does anyone have experience with the
Raytheon NMEA/SeaTalk bridge? I have an older one (4 years) that I'd
never used until recently when I bought a new Icom 502 and then I wired
in the bridge into my SeaTalk bus to transmit lat/lon info to the new
radio. When I first fire up the Autohelm GPS and the radio, it gets the
signal and the radio reads out the correct info, but after about 5
minutes of operation the radio data starts flashing and pretty soon it
reads "no data available." Because the bridge is solid state it's hard
to imagine that it works for a few minutes and then fails -- is this
possible? The bridge is wired into the bus in parallel with my
autopilot, and everything else on the bus is working perfectly. I want
to be sure the bridge is defective before I spend the $$$ to buy another
one; if it weren't for having to hook up another external antenna, it
would be cheaper to buy an inexpensive Garmin than to buy another bridge.

Jim


You need to be able to SEE the data to know what's going wrong.

If you are playing the NMEA 'game', An old laptop PC with a serial port,
running Windows 95 or upwards gives you Hyperterminal (optional windows
component - may need installing from the windows disks or CD) which lets
you SEE the NMEA data being transmitted. You will also need a 9 pin D
plug, wired Data to pin 2, Common to pin 5 (or Data A to 2, Data B to 5
for proper balanced NMEA 2.0 if there isn't a common.)
DONT RUN THE LAPTOP DIRECTLY FROM SHIPS DC POWER, THE SERIAL INPUT IS NOT
OPTOISOLATED. I recommend running it off its own battery if possible,
otherwise if its AC adapter only has two wires on the input side, that is
fine as well. You will usually get away with it otherwise but check for
voltage between pin 5 and the common or B wire of the NMEA feed BEFORE
connecting it. There mustn't be more than a fraction of a volt!

All you need to do then, is start Hyperterminal (in programs - accessories
- communications), give the new connection a name, select 'connect using'
- 'Direct to Com N' where N is your com port number (usually 1 on a laptop
with only one serial connector) and on the next dialog box, select 'bits
per second' - 4800, 'data bits' - 8, 'parity' - 'none', 'stop bits' - 1,
'flow control' - 'none' then OK that and you should start seeing the NMEA
sentences and you can then start checking that you've got the correct ones
being outputted. When you've done, it'll ask you if you want to save the
session. Good idea, then you dont have to remember the settings next
time.

With that out of the way, If the data to the laptop starts good then
vanishes or gets corrupted with nothing else connected, its time to get
the NMEA/SeaTalk bridge checked by an expert. If its not giving the GPS
sentences you need after the first few minutes but is giving valid data
from other instruments they may come back when you are moving! Otherwise
if it stays OK get the DSC radio checked.

A second GPS just for the DSC is a ****** good idea anyway so you have a
backup. It doesn't need to be fancy, a Garmin GPS12XL with the extra
mount, power/data cable and an external antennae would be perfect as that
model will run off ships power continuously and is also a good handheld
with a decent battery life (no mapping). The GPS12 is far less suitable
as its maximum supply voltage is 8V, the standard 12V convertor for it
does NOT have the data connection available and it has NO external
antennae socket although if it is located somewhere with a decent view of
the sky for its internal antennae and you get the right lead/adaptor for
it it can be used. I am not sufficiently familiar with the new Garmin
models to recommend one of them, nor other brands. The advantage of a
cradle mounted handheld is that in an emergency you can take it with you.
If you set up for this, a quick disconnect connector on the antennae cable
is essential, you DONT need to be trying to unscrew a screw on connector
in a hurry!
--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
*Warning* SPAM TRAP set in header, Use email address in sig. if you must.
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