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6 OPERATIONAL EXAMPLES OF APRS
TH-D72A/E CONTENTS 43
Refer to the diagram below to understand what occurs when both Decay Algorithm and Proportional
Pathing are used at the same time.
Figure 6-3 Switching between Decay Algorithm and Proportional Pathing
(when Stopped = 1 (knot); Moving = 3 (knots))
As the example above shows, when the mobile’s speed exceeds 3 knots, Decay Algorithm stops and
Proportional Pathing begins. Similarly, when the mobile’s speed drops below 1 knot, then
Proportional Pathing stops and Decay Algorithm begins.
Note: The Stopped value cannot be configured higher than the Moving value. Also, the Moving value cannot be configured
lower than the Stopped value.
SmartBeaconing was developed by Mr. Steve Bragg, KA9MVA, and Mr. Tony Arnerich, KD7TA, in
1998. SmartBeaconing uses the speed information that is received from the GPS receiver and
traveling direction to efficiently transmit the beacon. There are two factors that come into play when
determining how SmartBeaconing functions: distance traveled since last beacon transmission,
addressed by using Variable Rate Beaconing to change the transmission interval with speed, and
heading change since last beacon transmission, referred to as Corner Pegging.
When your mobile station is moving at a speed less than LOW SPEED as set in the menu, the
position beacon repeatedly transmits at the interval of SLOW RATE as set in the menu. When your
mobile station is moving faster than HIGH SPEED as set in the menu, the position beacon repeatedly
transmits at the interval of FAST RATE as set in the menu. And if your mobile is traveling at any
speed between LOW SPEED and FAST SPEED, then the beacon transmits at an interval that varies
linearly according to the speed traveled. The transmission interval extends longer as the speed
becomes slower, and the interval becomes shorter as the speed gets faster.
Table 6-1 Relationship between Speed and Beacon Transmission Interval
6.1.4 Simultaneously using Decay Algorithm and Proportional
Pathing
6.1.5 SmartBeaconing (Written by Steve Bragg, KA9MVA)
6.1.5.1 Variable Rate Beaconing (Transmission Interval Changes with Speed)
Speed Transmission Interval
Over HIGH SPEED FAST RATE
Under HIGH SPEED
Over LOW SPEED
(Only when HIGH SPEED ≥ LOW SPEED)
(Only when HIGH SPEED ≥ LOW SPEED)
FAST RATE x HIGH SPEED / current speed = transmission interval time
Under LOW SPEED SLOW RATE
Now
Proportional
Pathing
Returns
to Decay
Algorithm
Velocity (Knots)
Status
12203335
Decay Decay DecayProportional Proportional Proportional Proportional