Kenwood TH-D72A/E User Manual
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2 HOW YOU ENJOY APRS WITH TH-D72A/E (WRITTEN BY BOB BRUNINGA, WB4APR)
8
TH-D72A/E
Facebook on APRS
Purely as an aside, you can think back to the Kenwood VC-H1 handheld SSTV
device as an attempt (before its time) to add the visual aspect of social
networking to ham radio and APRS. This was a fantastic idea. And it was fully
integrated into all Kenwood APRS radios at the time, adding real-time video to
APRS digital and texting connectivity. You could think of the combination as
real-time “Facebook” on APRS. Unfortunately it was ahead of its time and the
VC-H1 handheld is no longer in production, but thousands of hams have them
and still use them. These SSTV handhelds along with readily available free
SSTV software make a great visual adjunct to APRS. This was in the early
2000 time frame before anyone had camera phones. Think of the potential.
Snap an image, and send it into APRS where it was picked up by a web site
that cataloged it by position, originator and a text description for viewing by
anyone. This can be a tremendous asset for ham radio public service. There
are a few such active links from APRS and SSTV to the web called the
Automatic Picture Relay Network, or APRN.
Refer to:
APRS Voice Alert
Three things dramatically brought back human connectivity to APRS. The first factor was Voice Alert.
The second was the addition of a Frequency field in all APRS position packets. And the third was the
emergence of VOIP Internet/ham radio linked voice. Voice alert is like a 3
rd
simultaneous radio
channel on the Kenwood APRS transceivers. It acts like an intercom channel for all APRS operators
to be able to quickly raise another nearby APRS voice alert station by a simple direct voice call. It
required no new hardware or software. It simply consists of setting CTCSS 100 Hz on the APRS
data channel and keeping the speaker volume up. This way, all packet noise was completely muted,
but the operator could still be called at any time with a CTCSS 100 Hz voice call. A secondary
benefit to this technique was a free proximity detector. If any other Voice Alert station got within
simplex range (maybe 5 miles or less) his periodic packets would give an audible alert. These new
features of APRS Voice Alert as indicated in the APRS Mobile Information Exchange drawing above
finally made it easy to keep the eyes on the road, but never miss the opportunity for human contact
with a fellow APRS operator on the open road. Voice Alert is now on the Function Menu in the
TH-D72A/E.
Frequency Data Field
At the nearly same time (2004), the Frequency field was added to the position packet specification.
This standardized the inclusion of a voice operating frequency in the APRS system. APRS was
never intended as an end-in-itself, but as a tool to be applied to all aspects of ham radio and human
contact. Knowing other station’s voice contact frequency in many cases is even more important for
establishing communications than knowing position. Now every ham could announce his monitoring
frequency in his APRS packet and could call others on their indicated frequency. Kenwood was the
first to leverage the value of this capability by releasing the TM-D710A/E in 2007. This radio (as well
as the new TH-D72A/E) not only automatically includes your voice band frequency in every position
packet but can also then tune to someone else’s frequency by simply selecting “Tune” as shown
below.