linking pc, autohlm 4000, Grmn 128, NASA GPS rep

[DAPPER]

I have managed to link the Garmin 128 to talk to the Autohelm 4000 and the NASA GPS repeater. Yet as soon as I connect the pc with Garmin cable 010-10150-00 the connection with the Autohelm and NASA GPS repeater ceases.
Who can help me with this please?

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[Twister_Ken]

Re: linking pc, autohlm 4000, Grmn 128, NASA GPS r

Garmin's service people have always been very helpful whenever I've had a query.

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[Guest]

Yahhjo Group ... GPS Nav

over 140 members contributing ....... I'm sure someone could help you ...

URL http://groups.yahoo.com/group/gps-navigator/

join us and I'm sure we'll find a way .....



<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[warrior40]

I usually use a sextant, a lead line and just lash the wheel when I need a free hand ..

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[DAPPER]

Thanks for the advice.

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[snowleopard]

i heard that nmea output is only supposed to produce enough power for one receiving device. i feed autopilot and dsc off my gps but in theory it's not guaranteed to work. you may need a repeater.

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[LadyInBed]

Re: nmea output

The NMEA standards allow a single "talker", and several "listeners" on one circuit.

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[paulrossall]

Re: nmea output

Does this mean I should be OK linking up my Garmin 12 with a Simrad TP30 and a Yeoman Plotter? Would the garmin be the "talker" and the other 2 listners? This is a massive move into the technological era for me and I am resorting to the old fashioned "I'll just keep my fingers crossed" method

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[snowleopard]

Re: nmea output

hope you're right, it would be a pain otherwise.

<A target="_blank" HREF=http://www.ybw.com/cgi-bin/forums/showflat.pl?Cat=&Board=pbo&Number=326613&page=&view=&sb=&o=&vc=1>here</A> is another thread where this was discussed



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[kdf]

Re: nmea output

NMEA is single talker, multiple listeners. What this means is that one station talks and all others can collect and process the info coming down the line. If you want to have multiple talkers ie: GPS, wind, depth all combining their infomation together so that say a PC or a Nav Repeater can pick it up you need either 1) a NMEA mux which has multiple inputs (one for gps, one for depth and so on) and one or more outputs (with all the data from all the inputs) or 2) a proprietary networked system like B&G or Ratheon where each instrument has an input and an output and each reads in the data from the previous instrument and adds their own, then outputs the combined data on the output port.

If you want to have mupliple devices all pick up a gps position from a GPS then you can connect all the devices to the gps output and keep your fingers crossed. It may work and usually does but as you add more and more listeners the output voltage level from the GPS drops and can reach a point where the data is unreadable.

Hope this helps.
-Kevin


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[Aeolus_IV]

Re: nmea output

When I asked this question there were two points made:

1/ NMEA0183 can have a small number of listenners attached to a single talker
2/ Not all equipment implements NMEA0183 correctly at the hardware level

The second point requires some explaining. NMEA0183 is a differential transmission standard, meaning that the two wires both carry a data signal, but one is the opposite of the other (hense labelling + and -). This is akin to RS 442 (always get the digits wrong on this one).

However some hardware cheats and uses cheaper RS 323 drivers for their NMEA0183 interface. This is an old fashioned signal and ground system. Sometimes you can mix these - sometimes you cannot. Your first step is to find out what each of the interfaces really is - then you'll know if you can mix and match, it sounds like you have a mixture.

Jeff.

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[MartinGPerry]

To answer the original question

I have a GPS128 with single NMEA out being split and going to:

Radar
Yeoman plotter
Autohelm 5000
ICS Navtex with NMEA repeater display
PC with charting software
Global GPS repeater

The input impedance of all these input devices is so high that the actual current they take from the signal is minutely small and I would expect to be able to hang more devices on the end before I saw any problem at all with signal degradation.

As everything is ok on your setup until you plug the PC cable in - then that is almost certainly where the problem lies.

Suggest you make your own PC cable, there are only three wires involved and if you visit http://www.garmin.com/support/faqs/faq.jsp?faq=68 you will see exactly the connections you need to make between the 128 and your PC

Martin





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