What I have learned about APRS, Garmin, D72A...

[KJ0NAS]

Hello all.  I recently got my tech license.  I got it because I saw the APRS episode of Hak5, so obviously I am interested in APRS.  Finding information on APRs has not been easy so I figured I would share some info that I have accumulated.

I picked up a used TH-D72A.  I want an APRS system for my car that will use my Garmin Zumo 550 (I know the Nuvi 350 is better for APRS, but this is what I have).  I also wanted something I could put on my motorcycle really quick so my friends and family can see where I am at on one of my trip.  I am not going to talk or use messaging while on the bike.  So I am just going to get a handle bar mount for the D72A and a mag antenna.  But I want a handheld for my bike just in case that ends up being my only available line of communication while I am out camping.

Yes, the D72A is a little underpowered for mobile use.  That is why I just picked up an amp.  My plan for the car is to get an antenna and keep the amp in the car.  So when I move the radio from my bike to car I just have to plug in the power and antenna.  THOUGH I am thinking about mounting a power supply and the amp in a smaller ammo can so I have a small go kit when needed.  It could fit in on of my saddlebags.

Ok, so there's the setup, why I got into ham radio/APRS and what I currently have and plan to do.  So what have I learned?

I want to have my D72A and Zumo 550 talk to each other.  Doing the messaging thing would be neat, not sure how often I would use it though.  Reading the internet I thought all I needed was either the FMI cable or Argent Data's GTRANS cable.  I picked both up.  The GTRANs worked but the FMI didn't.  This had me confused.  Plus the GTRANS was just doing waypoints, no messaging.  This is where the documentation out there is either vague or not very direct.  What I have found out is the GTRANS cable only does waypoints.  So it will be good for events and whatnot when you need to know where your personel are. 

In order to do messaging you have to use the FMI cable BUT you need something that can translate the Garmin protocol to APRS protocol.  As far as I can tell the OpenTracker is the only think with that capability.  However, it seems redundant to get that as the D72A already has a TNC built in, so all I would use from the OT is the Garmin part.  But that assumes the D72A and OT can talk to each other.  I think they would, I don't see why not.  I am thinking about making my own.  The Garmin FMI and APRS are serial protocols, I am a software developer.  I am pretty sure I can make a translator out of a netduino.

I know someone recently asked about a good HT to get.  The D72A ia awesome.  That person also asked abut being Mac friendly.  That's really hard to find.  Chirp works with the D72A (after installing a driver from the TNC chip's manufacturer) but you only get to manage memory.  I dual boot my Mac using Boot Camp because there are times when a Windows app is the only thing available.  The Kenwood program does everything you need, even program the buttons of the SMC-33 (or is it 34) speaker mic.  If you get a D72A I highly suggest the Nifty guide.  The stock manual just tells you the function of each button.  The Nifty guide actually tells you how to use your radio.  (For a new ham I also highly suggest the Nifty band quick reference)

I would like to use a mobile radio for my car.  If a thoat mic works well I would think about a mobile radio for my next bike (which wil be a touring bike).  I want dual band so I can have one band do APRS and voice on the other band.  This is where it seems very limited.  Otherwise I would go with the Alinco DR135 with the OpenTracker replacement board if I wanted a dedicated APRS setup.  But it seems like the way to go is the Yaesu FT-7900R with an OpenTracker3.  Ideally for my bike I would like Yaesu to update the FTM-10R to have a data port or built in APRS.  Well, there are the Yaesu and Kenwood APRS mobiles, but those are expensive.

[K0JEG]

You can message with the keypad on the D72, but you'll need to switch the TNC from Packet mode to APRS mode. After you send the message, switch back to packet mode. Depending on the hardware you're using, you might want to just keep the D72 in APRS mode, letting it beacon and all the other stuff, and just use your GPS as a display unit.

There is a program that started out on Linux called Xastir. It isn't the most friendly software in the world, but there is a Mac OS-x build that is well maintained. There is documentation available for getting it to work on mac with a D72.

Unless you're out in the wilds of Northern Montana, you should be just fine with 5 watts and a decent antenna. When I lived in an area without local digipeaters I used a 1/2 wave antenna on the back of my bicycle and it worked just great. Besides, 50W on a motorcycle might cause RF exposure problems. Even on I-70 in southern Utah ("next service area 150 miles") I get into digipeaters on 10 watts (TM-d700 on L power setting). Hwy 50 through Nevada was a different story however...

[KJ0NAS]

Right.  I am not going to use the radio while on the bike.  I know I can message from the D72, but it isn't as easy as with the fleet management stuff on the Garmin.

[W5DQ]

...... translate the Garmin protocol to APRS protocol.

Have you or can you select a different protocol on the Garmin GPS unit?

On my old Garman eMAP GPS unit, I can select either for it to speak 'GARMIN' or 'NMEA-0183'. Selecting NMEA-0183, the eMAP communicates with my Kenwood TH-D7A (granddad to your 72A). The eMAP provides waypoints and GPS info to the 7A and the 7A provides decoded APRS station location info to the eMAP which displays these on it's small display. Attaching a Byonics Tiny-Trak III to the computer port on the 7A and I can do APRS messaging via the 7A's APRS interface.

Gene W5DQ

[KJ0NAS]

NMEA is just standard GPS strings.  The Garmin protocol includes other stuff, like the information needed for fleet management.  I want to use the fleet management interface to send and receive messages.  But that's all I need since the TH-D72A does everything else.

[W5DQ]

NMEA is just standard GPS strings.  The Garmin protocol includes other stuff, like the information needed for fleet management.  I want to use the fleet management interface to send and receive messages.  But that's all I need since the TH-D72A does everything else.

Fleet of what? Cars? Boats?

Can't help you there as I don't know anything about Garmin's fleet s/w. Sounds like you need to get someone smart on Garmin interface protocols and develop a translator to do what you need. I would be really surprised if such existed as an off-the-shelf s/w pkg  - unless of course someone has been there before you and has done it and made it available in public domain 

Gene W5DQ

[KJ0NAS]

http://www.youtube.com/watch?v=Aum8Y3EK6yI

I am going to make it though I might just get an OT+.

http://developer.garmin.com/lbs/fleet-management/

Other than the OT+ I don't think it has been done.