SmartBeaconing™, when set up properly works well in most situations where an APRS beaconing device is being used in a moving vehicle.
Let me first state that the purpose of APRS is
not to draw line on a map that exactly traces your path. APRS is intended to provide situational awareness to those who are monitoring the APRS network. In the case of a moving vehicle, APRS can provide "here I am (the last time I beaconed)" information to others who need to know where you are.
Yes, you can string together a historical record of your position reports and draw your path on a map, but the accuracy of that line to your actual path will depend on how frequently you send a beacon that is heard by the receiver. The problem with sending beacons at a fast rate is that you will take up too much of the local shared-resource APRS infrastructure. The problem with sending beacons at a slow rate is that your line on the map won't trace your path very accurately.
Simply beaconing every 2 minutes will provide a reasonable approximation of your path when you are moving, but it may not catch every turn or bend in the road that you are travelling. Additionally, if you neglect to turn off your beacon when you park your car, you might send beacons every 2 minutes for hours that provide information about your position that is no different from what you transmitted 2 minutes ago.
SmartBeaconing™ was developed by Tony Arnerich KD7TA and Steve Bragg KA9MVA to address these problem. With SmartBeaconing™, if you are moving at a fast rate, you send beacons more frequently. If you are moving at a slow rate or not moving at all, you send beacons at a slow rate. Corner pegging is an additional feature of SmartBeaconing™ that attempts to capture your changes in direction by sending a beacon when you change direction by a certain amount. You can read more about SmartBeaconing™ here:
http://www.hamhud.net/hh2/smartbeacon.html
The key parameters to SmartBeaconing™ are (in
bold):
Low Speed -- If your actual speed is less than the Low Speed, your beacons will be sent using
Slow Rate.
High Speed -- If your actual speed is greater than the High Speed, your beacons will be sent using
Fast Rate.
If your actual speed is between Low Speed and High Speed, your actual beacon rate will be the Fast Rate times High Speed divided by your actual speed. The result of this is that when you are going fast, you send beacons more frequently and when you are going slowly, you send beacons less frequently.
The additional parameters for corner pegging are:
Turn Angle -- This is the minimum amount of direction change that you have to experience before corner pegging will kick in.
Turn Slope -- This increases your sensitivity to direction changes when you are moving fast and decreases your sensitivity to direction changes when you are moving slowly. In other words, if you are moving fast, it takes less of a direction change before a beacon is forced by corner pegging.
Turn Time -- This is minimum amount of time that has to expire before corner pegging can force a beacon. Imagine you are driving around in circles in a parking lot. Without Turn Time, the Turn Angle parameter would cause you to send beacons one right after another.
Yaesu has a separate APRS manual for the FTM-100D. You may have to download it from Yaesu's web site if it didn't come in the box with the radio. It contains good information about setting up your radio for APRS including a section on SmartBeaconing™. The FTM-100D has three different sets of SmartBeaconing™ parameters, so make sure the settings you are adjusting are the settings the radio is actually using.
It looks like the default SmartBeaconing™ values in the FTM-100D are:
Low Speed = 5
High Speed = 70
Slow Rate = 30 minutes
Fast Rate = 120 seconds
Turn Angle = 28 degrees
Turn Slope = 26
Turn Time = 30 seconds
Note that the speeds are unitless, so if your radio is set up for "mph" in APRS menu 11-3, those values are in miles per hour. If your radio is set for "km/h", those values are in kilometers per hour and they are not converted from miles per hour.
The default parameters are not bad and will result in you beaconing every 2.33 miles if you are driving between 5 mph and 70 mph. When you are stopped, you will beacon every 30 minutes.
My favorite settings are Low Speed = 5, High Speed = 90, Slow Rate = 12 min, Fast Rate = 80 sec. That gives me a beacon every 2.0 miles if I am driving between 5 and 90 mph and I beacon every 12 minutes when stopped.
One final point... APRS is dependent on the ability of digipeaters and I-gates to hear you. If, your transmitter is shadowed from the nearby digipeaters and I-gates, you may not be heard reliably. If there are no I-gates near you and you don't get picked up by a digipeater, your beacon may not make into the APRS-IS (and, thus, to web sites like APRS.fi). If there is other APRS activity in the area, your beacon may collide with someone else's beacon resulting your beacon not getting through. Increasing your beacon rate will only make things worse for everyone, so don't be tempted to do it.
