Single GPS antenna

edessa

edessa

Pre-takeoff checklist
Joined
Mar 4, 2014
Messages
329
Location
Highland Heights, OH
Display Name
Display name:
edessa
Does anyone know if you can use coax splitter with a single GPS antenna for use with a Stratus ESG and a GTN 650?
I have the Stratus ESG with a 42G15A-XT-1 GPS antenna.
 
It can be done. I don’t know if it is approved.
 
Aviation GPS antennas have (with very few exceptions) active amplifiers built into them, which means the unit connected to the antenna needs to supply power to it.
A splitter would have to isolate one power supply while allowing the other one to still power the antenna.
There are such things out there, but they cost as much as an antenna. This is one example:
allavionics.com

Passive GPS Antenna Splitter – AllAvionics.com

Passive GPS antenna splitter with excellent gain flatness for all GNSS frequencies. 2 outpouts, 1 input. BNC, TNC, & N Connectors Available.
allavionics.com allavionics.com

Do you really want to mess with the receive path of what might be your primary IFR nav source? Not even sure if you'd be in compliance with Garmin's installation requirements anymore.
I'd probably do it if my fuselage real estate was limited and I wanted to share one antenna for a transponder and a secondary GPS. But I'd still reach out to the equipment manufacturers first to see what they say.
 
AV8R_87 said:
Aviation GPS antennas have (with very few exceptions) active amplifiers built into them, which means the unit connected to the antenna needs to supply power to it.
A splitter would have to isolate one power supply while allowing the other one to still power the antenna.
There are such things out there, but they cost as much as an antenna. This is one example:
allavionics.com

Passive GPS Antenna Splitter – AllAvionics.com

Passive GPS antenna splitter with excellent gain flatness for all GNSS frequencies. 2 outpouts, 1 input. BNC, TNC, & N Connectors Available.
allavionics.com allavionics.com

Do you really want to mess with the receive path of what might be your primary IFR nav source? Not even sure if you'd be in compliance with Garmin's installation requirements anymore.
I'd probably do it if my fuselage real estate was limited and I wanted to share one antenna for a transponder and a secondary GPS. But I'd still reach out to the equipment manufacturers first to see what they say.
Click to expand...
I was just trying to avoid adding more holes to the fuselage.
As far as Garmin is concerned, I purchased the unit used repaired with an 8130. It's out of warranty and I'm sure Garmin wont talk to me since i'm not a dealer. They wouldn’t even answer my question regarding the STC paperwork and told me to contact my local dealer.
As Jesse mentioned it's the approval for adding the splitter from the feds that would be the biggest concern.
 
1. Yes, you can but it needs to be a gps specific splitter.
2. It's like pulling teeth to get a shop to do it
 
I don't have a 650 install manual handy, so I'll give you an example using the 430W manual:
Cable loss between the antenna and the receiver has to be between 1.5 and 6.5dB for most antennas, with some requiring a cable loss of between 3 and 7dB.

RG-400 cable has about 1.5dB of loss per 6.5ft. There's probably 10-12ft of coax between the antenna and the radio in a 172 or similar sized airframe, variable with antenna position. So let's say 3dB of loss. Each connector adds about .15dB of loss. You have six of them (1 at antenna, 4 at the splitter, 1 at the radio), so 0.9 dB of loss. The splitter will cut the power in half, plus a few other losses, manual states -3.6 – 6.0 dB, -4.8 dB typical. Add them up, you're at 8.7dB of loss and out of Garmin's requirements.

Also, the install manual doesn't say anything about installing splitters. It shows a direct connection between the unit and the antenna. You put a splitter in there and they might say that you're not in compliance with their STC. Something goes wrong, it's your fault. That's a good reason for a shop not to touch this with a 10ft pole. Garmin has (or used to have) good product support, where they would answer such questions. I doubt they would give you an OK to install a 3rd party splitter that they've never evaluated themselves, even if the loss margin was ok.

(Here's a funny Garmin support story - there used to be a guy there named George Kelsh (sp?). Very helpful, he would always get things sorted out for you. Before Garmin, he worked at Bendix/King, same level of support. People would call him at Garmin to ask him Bendix/King questions, despite his best efforts to tell them he couldn't do that.)
 
edessa said:
Unfortunately not. Manual states to install it on top.
I'm just going to install the second GPS antenna.
Click to expand...
How about replace the ANTCOM antenna with a GA35 for the GTN and then have the GTN feed GPS data to the Stratus? Is it possible to dumb an ESG down to a ES? If not, is the tray compatible with an ES so you can swap with someone?
 
You must log in or register to reply here.
Back
Top