Mobilinkd TNC2



APRS or Amateur Packet Reporting System is a perty cool system.  It makes it easy to send messages and position information over an RF link to others in the area.

With the MARC group (http://marc-hq.org) we use APRS on our motorcycles and SAG (Support and Gear) vehicles.  This lets net control know where we are, but also makes it easier fro a SAG to find a motorcycle when when additional support is needed.

Some of our motors are equipped with a device called a tracker.  This is a transmit-only device that sends the rider's location at specific time intervals.  I have a couple of issues with this.  First, since it's transmit only, it can't listen first to make sure it isn't transmitting on top of someone else.  Second, it can't be a digi-peater.  A specialized device that extends the range of the APRS network.

The other thing I don't like is transmitting location information at fixed intervals.  This can lead to unnecessary transmissions (like while stopped), and also missed turns.  Smart Beaconing deals with these issues.  With smart beaconing, the transmitter will send a location report when the motorcycle has moved a certain distance, change it's heading, or an amount of time has passed since it last reported.

What does this look like?  When on a freeway and going around a slow bend, smart beaconing will cause a report to go out each time the heading changes more that about 15 degrees (or whatever you have it set to).  If are on a long straight highway, it will beacon when you have traveled more than a mile.  If you are stuck in traffic and haven't change heading, or moved more than one mile, for 15 minutes then it position report will be sent out anyway.  Just to keep your location fresh.

For charity bicycle events, smart beaconing makes a lot of sense.

I decided to implement APRS on my motorcycle using the Mobilinkd TNC2.  I connected it to a Baofeng UV-5R, using a cable I purchased directly from Mobilinkd.  The TNC2 is a small device that has a battery built-in.  I found that I can run an all day event on the battery in the TNC2 and the UV-5R without any problems.  This requires no power connections to my motorcycle battery making installation really easy.

I'm using the RAM Mount RAM-HOL-BC1U to mount the radio on my bike.  To mount the TNC2 I purchased some stand-offs at Home Depot and mounted a small plate on the back side of the RAM Mount.  I then velcro the TNC2 to the plate.  This setup has worked great for me.

I should mention that this isn't a stand-alone system, the TNC2 is just a TNC so it does require something to drive it.  I'm using APRSdroid on my phone and a Bluetooth connection to the TNC.  It was easy to setup and works great.






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