Primarily for general aviation discussion, but other aviation topics are also welcome.
By Rjk983
Apologies for starting another EC question - maybe it needs its own forum now :D

We have a bendix king kt74 fitted in our RV. We are getting a paw for ADSB IN and PAW/FLARM.

But I notice that the PAW can also be used as a position source via an extra usb-rs232 cable.

I’ve been googling and it looks like some have tried to use the PAW with the KT74 but with no success (going back to 2015 or so).

Has anybody managed to get it working? If not has anyone managed to get any Non certified gps source working?

@robp, @paulsengupta any pointers? I only ask as you both chipped in to those old discussions.
Because of where our PAw is mounted on the rear wall of the luggage compartment it is a long way from the KT74. For this reason we have never considered trying to link to the transponder and have simply bought the certified Trig with the EC rebate.

Sorry if that isn't helpful

Rob P
I believe Rob tried it with his old Skyforce (?) GPS and it didn't work? The Skyforce isn't WAAS/EGNOS though I don't believe. The PAW GPS is.

I have no personal experience with this. I don't know how the KT74 knows it has a "certified" GPS attached, whether this goes on input (ARINC vs RS232?) or whether it looks at the WAAS/EGNOS flag in the messages or something else.

What I did do was ask the BK representative at one of the major US shows. He pointed me towards a "secret" menu where you could go in and specify it. I had wanted Rob to try this at the time to see what happens but he had better things to do with his time like fly... :D

So the answer I have to give is..."Shrug". I don't know. I'd like to experiment and try it, but so far no one has bought me a KT74 to experiment with! :clown: You could experiment and report back. All it takes is a £3 interface from China and a bit of wire, so if you don't blow anything up in the meantime by wrongly connecting something, it won't cost much more than time to find out before shelling out on one of those Trig GPSs (though if you haven't claimed your EC rebate, you could do so buying one).
Last edited by Paul_Sengupta on Wed Jan 06, 2021 7:21 pm, edited 1 time in total.
Actually quite helpful - I started off looking at the trig TN72 and convinced myself it was the way to go but then spotted the paw output and confused myself!

On first view it looked like the PAW would be the simpler option if it could work as it was only one additional cable, but the TN72 does have the advantage of giving SIL 1.

I presume you also need to get the trig GPS puck?
I also asked someone from Trig, but they would neither confirm nor deny the fact that it was the same internals...but they did say that *if* the transponder were the Trig transponder, then they'd have expected BK to have their own requirements in their programming, perhaps via this "secret" (probably just the setup) menu.

Rjk983 wrote:I presume you also need to get the trig GPS puck?

I suspect it would need some sort of antenna...

Why not get an RS232 cable and try it from the PAW first if you have easy access to the connector on the back of the transponder?
@leemoore1966 thanks Lee, that is one of the posts I found earlier.

I was hoping it had been tried again more recently! As usual I’ve left it to the last minute and probably don’t have time to experiment with the PAW (which we are about to order...) and still get the rebate if we end up having to go,for the trig. so will do a bit more thinking about how we get ADSB out.

welkyboy wrote:Buy SE2 instead?

It was one of our considerations, but we have decided on PAW for “in” as it displays all types, and we already have a transponder that is capable of ADSB out so we’re hoping for a simple enhancement.

SE does give us a redundancy option for ADSB in if the PAW were to be u/s so is still in the mix.