WAAS GPS/ADS-B question

[Dean Pichon]

I have decided upon the uAvionix echoUAT unit to provide ADS-B in and out for my RV-4. My aircraft has an existing GPS antenna connected to a Garmin SL-60, but I don't have a WAAS GPS source, so had planned to install the integrated (antenna + receiver) SkyFYX unit offered by uAvionix.

Now, I am second guessing myself and would like to know whether or not I could use the existing GPS antenna (or a new one in its place) with a GPS splitter to provide signal to both my SL-60 and the SkyFYX variant that requires an external antenna.

The benefit to me is that I would not need to install another antenna, and would avoid running the associated wire(s). The downside is that I would need to buy and install a splitter something like this:

https://www.gpssource.com/collection...d-gps-splitter

Thoughts or recommendations appreciated.

Thanks,

Dean

[Carl Froehlich]

You answered your own question:
- SL60 uses and external GPS antenna
- The SkyFLX is an integrated GPS antenna and receiver in the one puck.

These are two different animals and not compatiable.

The SkyFLX that has an external antenna might work with a splitter, but I’m very skeptical. Considering the gross price of a GPS splitter along with odds that it would not meet the WAAS requirement I would look at other options.

If you ever plan on using this plane for IFR work, this might not be the best path.

Carl

[Dean Pichon]

Originally Posted by Carl Froehlich

The SkyFLX that has an external antenna might work with a splitter, but I?m very skeptical. Considering the gross price of a GPS splitter along with odds that it would not meet the WAAS requirement I would look at other options.

If you ever plan on using this plane for IFR work, this might not be the best path.

Carl

Hi Carl,

Thanks for the reply. The SkyFYX with the external antenna is the one I am considering for use with a splitter in this scenario.

Every so often, I consider a major panel upgrade to incorporate IFR capability, but the task is so large given my current equipment that "throwing away" the uAvionix ADS-B solution does not bother me.

Thanks again,

Dean

[flightlogic]

I will let you decide which avionics is best for your situation, but I don't agree with splitting a GPS signal. I know they make the splitter and charge $300. But a gps signal is very very weak by design. Splitting it further risks poor performance.

[BobTurner]

It?s potentially much worse than just losing half the signal. Some antennas have built in amplifiers requiring dc voltage running up the coax. Some have different gains than others (look at the mess the early 4xxW Garmins had when they used an OEM antenna). Unless you are absolutely sure you know what you?re doing I would never suggest a splitter for this application.

[Larco]

IIRC the GA56 NON waas antenna is quite popular and used with the SkyFYX that requires an external antenna. They can be found on Ebay or here VAF classified for not much money, far less than a spitter that will probably not work. I know of at least 2 RVs using this same set up as you with this antenna. Recommend checking with Uavionix of course.
When upgrading the 430/530 to WAAS the GA56 became surplus so they sell pretty cheap and now used on several ADSB systems like Uavionix.

[Veetail88]

Originally Posted by Larco

IIRC the GA56 NON waas antenna is quite popular and used with the SkyFYX that requires an external antenna. They can be found on Ebay or here VAF classified for not much money, far less than a spitter that will probably not work. I know of at least 2 RVs using this same set up as you with this antenna. Recommend checking with Uavionix of course.
When upgrading the 430/530 to WAAS the GA56 became surplus so they sell pretty cheap and now used on several ADSB systems like Uavionix.

Pretty sure you need a WAAS gps for proper adsb out reporting, no? Or does the SkyFyx put out a proper WAAS signal with a non-waas antenna?

[RONSIM]

No issues, with several FAA reports asked for and rec'd ---- always clean. Always worked fine with Navworx, previously.

Ron

[BobTurner]

Originally Posted by RONSIM

No issues, with several FAA reports asked for and rec'd ---- always clean.

Ron

As has been discussed previously, the fact that a gps is working today, or last week, or on a hundred straight days does not mean that it will work under the worst case scenario where it is still supposed to work. e.g., Does it meet the performance spec? Almost no RV owners can answer that question. I?d call uAvionix and ask them if their promise of meeting specs is still valid with this antenna.

[Dean Pichon]

Thanks to all for the posts. The questions, concerns, and advice have helped with the inquiries made to the various suppliers.
So far, I have had preliminary conversations with Garmin, uAvionix, and GPS Source the division of General Dynamics that makes this splitter.

Originally Posted by flightlogic

But a gps signal is very very weak by design. Splitting it further risks poor performance.

Originally Posted by BobTurner

It?s potentially much worse than just losing half the signal. Some antennas have built in amplifiers requiring dc voltage running up the coax. Some have different gains than others (look at the mess the early 4xxW Garmins had when they used an OEM antenna). Unless you are absolutely sure you know what you?re doing I would never suggest a splitter for this application.

The GPS splitter I'm investigating amplifies the received signal. It can be configured to use a DC voltage provided on the coax by the GPS receiver or can accept an external supply.

The Garmin aviation tech rep I spoke with said the use of a splitter in this application is common. (Though, to be honest, I have not heard from anyone who has done it.) He admonished me to make sure to get the correct voltage for the splitter. The antenna that came with my SL-60 uses 5VDC according to the drawing I found for it on the internet.

Originally Posted by Veetail88

Pretty sure you need a WAAS gps for proper adsb out reporting, no? Or does the SkyFyx put out a proper WAAS signal with a non-waas antenna?

Originally Posted by BobTurner

As has been discussed previously, the fact that a gps is working today, or last week, or on a hundred straight days does not mean that it will work under the worst case scenario where it is still supposed to work. e.g., Does it meet the performance spec? Almost no RV owners can answer that question. I?d call uAvionix and ask them if their promise of meeting specs is still valid with this antenna.

The SkyFYX unit is a WAAS GPS receiver. According to uAvionix, the SkyFYX unit will work with my installed GPS antenna. This is a key issue and I will probably have a 2nd conversation with uAvionix to confirm, once I have all the details specified for the splitter.

I need to have a deeper conversation with GPS Source to determine connector specifics, EMI issues, and so forth. I also need to confirm the 25dB of gain provided by the splitter is acceptable to both receivers. There are probably other issues I have not yet considered, but this is what make this fun.

Thanks again for all the help.