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Garmin GPS antennae question

Weefle

Well Known Member
Please school me in the GPS antenna world.

I will be installing a GTN 650 and a GNC 355. Both obviously need GPS inputs. How do they share the signal? Is it via RS232, ARINC or? I can't imagine having to mount separate antennas for both.

Thanks

Keith
 
GPS Antenna

Please school me in the GPS antenna world.

I will be installing a GTN 650 and a GNC 355. Both obviously need GPS inputs. How do they share the signal? Is it via RS232, ARINC or? I can't imagine having to mount separate antennas for both.

Thanks

Keith

Hi Keith,

You will need to mount a GA 35 antenna for each of your IFR GPS Receivers, on top of the aircraft. They are independent IFR Navigators, you wouldn't want an issue with one of them to affect the operation of the other.

Thanks,

Justin
 
But why two (very expensive) TSO GPS navigators?

I assume you will also have an EFIS with its own GPS antenna as well.

Carl
 
But why two (very expensive) TSO GPS navigators?

I assume you will also have an EFIS with its own GPS antenna as well.

Carl

Good question Carl,

My bucket list is to cross the pond one day to Europe with the 10. In Canada I have to have two nav sources for IFR. Rather than a GTN650 and GNC 255 I opted for the GNC 355. I'd rather have 2 GPS than 2 VOR/ILS units.

Cheers,
 
There are GPS splitters out there that should work for you. There are some technical limitations to them. Most allow only one of the GPS receivers to pass power to the GPS antenna (DC PASS), and all other receivers DC power is blocked. This means if you the GPS receiver plugged into the GPS PASS port loses power or fails, neither GPS receiver will receive a signal. There are some brands out there that will allow multiple GPS receivers to pass DC power, or be powered externally.

I use one of them for all of my non-IFR receivers (G5's, ADS-B receiver) and it works great.

I don't know the legality of using them in conjunction with an IFR receiver. But I am certain a splitter would work for what you are accomplishing to do!

One example:
https://www.instockwireless.com/gps221-outdoor-tnc-gps-splitter.htm
 

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Why not use a GPS + a VOR antenna into the 650 ??

My understanding of Canadian ifr rules is ‘two independent nav sources’. Since a failure of the 650 could remove two nav sources, it only counts as one. Canadians need a second, independent box. My guess is that using one antenna for two receivers also falls under this rule if any active electronics are involved (?).

Likewise, great care, and some knowledge, is needed before using a splitter. Some gps receivers are designed to deal with incredibly weak signals from passive antennas (no electronic amplification in the antenna itself). Others are designed for stronger signals from an antenna with a pre-amp. Usually these two types of receivers cannot share an antenna. Someone else commented on potential issues if both receivers are trying to supply DC power.
 
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