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Has anyone used a Garmin GPS 18X to drive their ELT?

snopercod

Well Known Member
I fly with a ACK E-04 ELT, but the GPS input isn't connected since I don't have a panel-mounted GPS (I'm a Stratus/ForeFlight guy.) Since I do a lot of flying over remote, mountainous areas, and don't usually file flight plans, I got to thinking it might be worth $70 to add a GPS signal to the ELT:
For new generation 406 MHz ELT?s without GPS position information, the average time to process, and identify the aircraft location is 1-2 hours, with a search radius of about 2 miles or less. With GPS information, the time to locate the aircraft position is 10 minutes or less, with an accuracy of about 300 feet.​
The Garmin GPS 18X looks like a hockey puck with wires and provides an RS-232 output for driving other equipment, plus power wires. The -PC version takes 8?30 Vdc and the others need 5V. The cost on amazon is $66.95. The ELT manual has instructions for hooking up the GPS 18X, but I can't find any information on programming it. Apparently it has to be hooked up to a comm port on a computer via some mystery adapter cable and some mystery software. Also, one must provide ship's power to the ELT - to power the RS-232 transceiver I assume.

Has anybody done this? How painful is it?
 
I have the GPS 18x as my primary gps. Feeds my EFIS, Trutrak autopilot, APRS transmitter, and the ACK E04 ELT. It was five years ago, but no computer hookup or programming required.

You do need to make sure the GPS and ELT are set for the same baud rate (9600 in my case), there is a jumper in the ELT. The manual has guidance on how to make a test light with an LED that is used to verify the GPS position is being received. You also need to provide ship power to the ELT to run the electronics that process the position data.

I wish they would have used a different connector than the mini din, but it works fine.
 
Thank you!

I have the GPS 18x as my primary gps. Feeds my EFIS, Trutrak autopilot, APRS transmitter, and the ACK E04 ELT.
Oh thank you! So how does one connect more than one RS-232 (TIA 232-F, actually) device to the GPS 18X? Certainly there must be some sort of interface in there, right? A Trutrak autopilot is on my wish list so it would be great if this little device could feed it as well.
 
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Oh thank you! So how does one connect more than one RS-232 (TIA 232-F, actually) device to the GPS 18X? Certainly there must be some sort of interface in there, right? A Trutrak autopilot is on my wish list so it would be great if this little device could feed it as well.

Hello Snopercod,

The GPS 18X is a great little unit, but don't forget that it doesn't know anything about navigation, so if you want to drive your autopilot with a lateral deviation signal so it can follow a direct-to or a flight plan, you will need a real GPS navigator. For only $749, it is pretty hard to beat the Aera 660. It also has two serial ports and can provide NMEA to your ELT (and much more).

http://www.vansairforce.com/community/showthread.php?t=135203

PortraitMap15_7.jpg


Thanks,
Steve
 
For only $749, it is pretty hard to beat the Aera 660.
Very true; I really like that powerline feature. In my case, though, I already have a Stratus 2 and ForeFlight for my iPad. I can't see buying an Area 660 just to provide a GPS source for my ELT. Thanks for the suggestion, though. Does Garmin offer any notes on interfacing the GPS 18X to other equipment?
 
my experience

I also have a Garmin GPS 18x purchased from Amazon in both RVs as a backup GPS as GPS2 into my GRT EFIS and GPS1 into my Trutrack ADI. Just wired the output in parallel into both. I did not reconfigure the GPS 18x, just went with the factory setup and setup the GRT and no setup needed for the ADI. It works great in my RVs.
 
Thanks

Just wired the output in parallel into both.
That is so weird. A serial interface "talks" to the hosts and they talk back when the device is ready to receive. It seems like wiring two hosts together would confuse things. I guess I don't understand all I know about RS-232. Did you keep the DB-9 connector that comes with the GPS-18 or cut if off and just splice the wiring direct?
 
Like Tom said, just split it into your multiple receivers. It's a send-only interface, the only time I ever needed to talk *to* the GPS18 was on initial config to set up the sentences and baudrate...you only need to connect the ground and tx lines. I have a DB connector with a wire soldered across the top row, and one across the bottom row, that works as a distribution bus of sorts for the NMEA signal. I have a second one for Icarus altitude, as well.
 
my reply

They do not talk back, there is no acknowlegement, just data going from the gps to multiple inputs. in my case it does not confuse either device. I cut off the connectors that came with the GPS18, and just spliced in my two "loads", works great in my case. Found multiple post about the wiring info.

The data sheet that came with the GPS 18 had the info required to setup the GRT port.
 
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Design Notes on TIA/EIA-232-F Protocol

If anyone is interested in the details of the protocol, here are the Design Notes from Texas Instruments Interface Circuits for TIA/EIAĆ232ĆF. It seems like the data output of the GPS 18X should be between Pin 3 [Transmit Data Line] and Pin 5 [Signal Ground] of the DB9 connector. All the other pins have to do with handshaking or receive data.
 
And there are dozens of other serial output GPS modules that will do the same thing, often for <$20.

When I built my RV-7, I used one of these cheap GPS receivers as a second GPS input. One day I was flying along and all of my GPS's failed - I wasn't receiving any GPS serial data on the cheap GPS receiver, and my Garmin 430W was reporting it couldn't lock onto any satellites, along with my iPad mini couldn't get a valid GPS position.

It turns out my cheap GPS failed in a way that it jammed all of the other GPS receivers on my airplane. Since I didn't have a switched power source to that GPS, I couldn't shut it off.

I decided to spend the good money for a Garmin 18X OEM LVC receiver. It has worked flawlessly since I installed it in 2013. I'm not trying to say the Garmin 18x doesn't have the potential of failing the same way the cheap GPS receiver did, but my money is on the Garmin GPS receiver definitely being higher quality and less likely.

Full writeup:
http://rvplane.com/?categoryid=10000&dayid=1112
 
Just search for 'serial gps' or 'gps serial output'.
Thanks, Charlie. Man, they really are cheap, aren't they. I'm thinking that for the price difference, I'll probably go with the Garmin 18X, though. I trust Garmin not to let me down if I'm crashed out in the mountains somewhere.

Do I have this right that if your ELT is connected to a GPS, it pings the satellites every so often so the rescue folks can predict where you will be?
 
Do I have this right that if your ELT is connected to a GPS, it pings the satellites every so often so the rescue folks can predict where you will be?

My understanding of it is, no. The ELT is processing each position received and storing it in it's memory. When your ELT goes off, it uses the last GPS position it received to transmit to the sats with the distress signal. I believe I've read that the stored GPS position is considered valid for only a certain number of seconds (and not transmitted if it's expired), but I can't find documentation to back that up now.

ACK E-04 FAQ said:
How does the ACK E-04 handle the GPS data input?
The E-04 receives the data input from your GPS once per second. The ELT uses the last data received from your GPS as its location when the ELT is activated either manually or by the crash sensor.
 
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