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Wed Nov 18 21:02:00 UTC 2009


two environments in what later evolved into the topic of this report,
BLENDED APRS DEVELOPMENT.  At our planning meeting for the NWAPRS Summer
Gathering Scott (N7FSP), brought up "Blended APRS Networks" to allow the
sharing of APRS information across the various networks in the area so that
users were able to better share information between networks without the use
of the Internet. Simply put, we haven't discovered an easy way to implement
the crossband sharing of data specific to a mountaintop WIDEn-N digipeater.
Our work continues.

In steps Scott (N7FSP), and Casey (KJ7XE), who both have interest and most
importantly, mountaintop access, where development of a VHF 9600bd
experiment could continue. Scott settled on 144.35Mhz as it appears widely
under-utilized across the spectrum. The real "jewel" in this development was
the reduction in implementation cost by combining a Kenwood TM-D700 and
external Kantronics KPC-3 to come up with one "easy" digipeater package
resulting in 1200bd and 9600bd APRS on VHF with no need for another (UHF)
antenna, feed line or coax, or other ancillary equipment needed to install a
separate UHF radio at the remote location. The Kenwood D700 is configured to
digipeat APRS on the radio's A band on 144.35Mhz and internal TNC at 9600bd,
while the B band is tuned to 144.39Mhz and uses an external KPC-3 set at
1200bd. The cost savings is better than two separate radio systems at the
mountaintop, and upgrading a typical VHF radio plus KPC-3 digipeater is
easy; just replace the radio with a Kenwood TM-D700 and you're in business
on two freqs, one at 1200bd and the other 9600bd. The XTAL/CRYSTL digipeater
is the FIRST true "Double Sided Digi" (quote to K7MCR) that we know of.

OK, so we have lots of room for growth at the 9600bd environment, which
means more data can be pumped to the users on 9600bd. We're still working
out exactly what we want to expand with, but for the most part there's room
for those 10 second trackers or club announcements and flood closure
warnings or whatever.

Now comes the problem we're attempting to resolve now, with our BLENDED APRS
DEVELOPMENT project. As it exists now, two mobile travelers, one on the
primary freq 144.39Mhz at 1200bd, and the other on the secondary freq
144.35Mhz or 440.800Mhz at 9600bd, both driving down I-5 equipped with
Kenwood TM-D710 radios and AvMap G5 GPSs, neither will know of each other's
presence unless they're both communicating on a common voice frequency. A
nearby home station, typically setup for the primary freq, will only see the
one station unless his APRS application, typically UI-View, is also pulling
data from the APRS-IS. Many don't, relying only on the RF picture plotted on
their screen. Another nearby home station, new and improved, but monitoring
only the secondary freq with a 96kb-only TNC, will see only the one station
unless his APRS application is also pulling data from the APRS-IS. A third
home station, pulling only the APRS-IS feed, may see both stations while the
fourth home station, with deeper pockets, has UI-View running on his
computer connected to a KPC-9612 and two radios, one on 144.35Mhz or
440.800Mhz and the other 144.39Mhz.



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