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GPS multiple feeds - how many?

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Phil White

Joined: 10 Jan 2006
Posts: 45
Location: Downers Grove, IL

Posted: Mon Nov 02, 2009 7:58 pm Post subject: GPS multiple feeds - how many?

I am building an RV-10, and beginning to assemble and wire a panel.  My 

main GPS is a Garmin 396.  I need it to feed my GRT EFIS, a Tru-Trak 

autopilot, and a 406 MHz ELT.  Will I have any problems with impedance 

matching, or signal degradation if all 3 are fed from the GPS directly?  

I don't know the input impedances of any of these fed boxes, or what 

sort of power the Garmin can generate on its RS-232 feed.

    I read the 2007 post about using a DB25 connector to facilitate the 

multiple connections, but wonder if one needs a buffer or amplifier of 

any sort to handle 3 outputs from one.

Phil in IL

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melvinke(at)coho.net
Guest

Posted: Mon Nov 02, 2009 9:05 pm Post subject: GPS multiple feeds - how many?

My Garmin 395, and now a 496, drives a Trutrak autopilot, Argus 5000,  

and automatic position reporting transmitter perfectly well, without  

any consideration of impedance compatibility. Consultation with Garmin  

tech support had indicated that these portable GPS units are expected  

to drive three devices without degradation of signal. and I can  

confirm that. I tied together the five pins of a DB9 connector as a  

"NMEA-bus", and it works well.

Kenneth Melvin, N669TJ, RV-9A

On Nov 2, 2009, at 7:38 PM, Phil White wrote:



 	  Quote: 	
		   

 >



 I am building an RV-10, and beginning to assemble and wire a panel.   

 My main GPS is a Garmin 396.  I need it to feed my GRT EFIS, a Tru- 

 Trak autopilot, and a 406 MHz ELT.  Will I have any problems with  

 impedance matching, or signal degradation if all 3 are fed from the  

 GPS directly?  I don't know the input impedances of any of these fed  

 boxes, or what sort of power the Garmin can generate on its RS-232  

 feed.

   I read the 2007 post about using a DB25 connector to facilitate  

 the multiple connections, but wonder if one needs a buffer or  

 amplifier of any sort to handle 3 outputs from one.

 Phil in IL

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MauleDriver(at)nc.rr.com
Guest

Posted: Tue Nov 03, 2009 5:28 am Post subject: GPS multiple feeds - how many?

I have a 396 (not in the '10) and all those other components but I can't 

answer your question.



It occurs to me that a cost effective solution may be to simply add a 

$150 external GPS from GRT.  It can drive at least the EFIS and the AP.  

And it would be  permanently mounted like the EFIS and TT though I'm 

sure you are planning to 'permanently' mount the 396.



Bill "just finishing up the panel and going back to fiberglass" Watson

RV10 40605



Phil White wrote:

 	  Quote: 	
		   



 I am building an RV-10, and beginning to assemble and wire a panel.  

 My main GPS is a Garmin 396.  I need it to feed my GRT EFIS, a 

 Tru-Trak autopilot, and a 406 MHz ELT.  Will I have any problems with 

 impedance matching, or signal degradation if all 3 are fed from the 

 GPS directly?  I don't know the input impedances of any of these fed 

 boxes, or what sort of power the Garmin can generate on its RS-232 feed.

    I read the 2007 post about using a DB25 connector to facilitate the 

 multiple connections, but wonder if one needs a buffer or amplifier of 

 any sort to handle 3 outputs from one.

 Phil in IL

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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