Kenwood TM-D710GE - Manual (Page 8)

4
01 APRS Operation (Written by Bob Bruninga, WB4APR)
This data from Steve Dimse’s FINDU is plotted on APRSdos to show the user density in the USA in February 05 (2008).
Although it appears that most of the USA is low density, remember that a WIDE5‑5 launched anywhere in the remotest
area will still get to the cities and add to the QRM there. And there are 100 times more low density users surrounding
these cities on all sides that really adds up to heavy QRM. We recommend WIDE2‑2 in the 8 per degree or more and
surrounding areas. 3‑3 should be used only in the 5 per degree or less areas.
The grid size is 30 miles and each is averaged with all 8 of its surrounding adjacent grids. The file is over 11,000
stations.
But the great news is that the New n‑N Paradigm is the right approach. It encourages WIDEn‑N everywhere while letting
the high density areas trap large values of N to prevent overload in their areas only.
APRS Global Internet System
Although APRS is a local, tactical real‑time two‑way communications system, the enormous free bandwidth of the
Internet was added in the mid 1990s to allow global monitoring of all real‑time data from all local communities around
the world. Everything on any APRS frequency is being monitored locally and fed globally into the APRS internet system
by hundreds of IGates. See live list (complete) or a Map of I‑G symbols.
Not only does this allow for global monitoring of any local activity, it also allows two‑way point‑to‑point messaging
between any two APRS users anywhere on the planet (that has an APRS infrastructure). Think of it as everything goes
in, so it is available to everyone, but the only things that come from the Internet back to local RF are messages and
selected position data requested locally.
KENWOOD Contributions
KENWOOD has developed its series of transceivers, the TH‑D7, TM‑D700 and TM‑D710 to best support the original
objectives of APRS. The display of APRS information on the front panel of these transceivers gives the mobile operator
instantaneous access to all local information being provided on the APRS channel about all surrounding ham radio
activities.
There are many APRS clients and programs that have been written that sometimes have concentrated too much on the
display of maps and vehicle positions while leaving out much of the original fundamentals of APRS and the efficiency of
the APRS network in support of two‑way local area communications. The KENWOOD transceivers have avoided that
simplistic approach to APRS by implementing a rich and full feature set that includes most of the original APRS features
that enhance this local information distribution concept. The KENWOOD transceivers are not just Vehicle Tracking
Systems, but are designed to be Real‑Time Information Distribution Systems for mobile operators with these features:
• Position Entry: The transceivers are not dependent on GPS for their value since manual position entry and 5 common positions
can be saved.
• Map Displays on attached GPS: Although these transceivers provide Map plotting via attached NMEA GPS units with map
displays, the radios are fully functional without maps and can display on their front panel all aspects of bulletins, messages,
weather, as well as information on the direction and distance to others including their antenna heights and gain.
• APRS Network Fundamentals: KENWOOD fully implemented the more subtle aspects of the APRS fundamentals that assure
optimum network efficiency and channel sharing among all users. The TM-D710 transceiver supports the decay algorithms and
proportional pathing. These two techniques provide good refresh rates for new and local information while minimizing the network
impact of old and distant data.
• Objects: The KENWOOD transceivers fully appreciate the value of APRS objects and display them prominently. The object
location is shown just like other stations either on the attached map display or on the front panel with distance and range. These
objects are what give APRS the local information value to local users.
• Two-Way Messaging: Unlike passive one‑way tracking devices, the KENWOOD transceivers provide the mobile user with full
two‑way messaging and display. This real‑time human‑to‑human communications is what makes APRS so valuable in support of
special events and emergencies.
• Field Data Entry: Although the KENWOOD transceivers are excellent field data display devices, their menus have also been
designed for easy data, position and message entry. Often overlooked is the ability to use a number of TH‑D7A/E or even
TM-D700A/E transceivers as excellent field data entry and clipboard entry devices at many field events. See http://aprs.org/
aprsevent.html .
• Individual Information Access: The KENWOOD individual radio displays enhance the distribution of ham radio information to a
large number of users by giving them individual front panel and key pad access to all of the online APRS data. A common mistake
of fixed operations with computers is the use of large display screens for large groups to see but which fails to recognize that
each individual viewer actually needs access to the keyboard to truly access the individual APRS information he may need at any
instant. The individuality of APRS radios with individual displays spreads this data access throughout the field.