[aprssig] This Year's Cross-Country Road Trip With HF APRS
Stephen H. Smith
wa8lmf2 at aol.com
Sun Aug 30 23:26:23 CDT 2015
This year, as usual, I made the annual cross-country road trip from central
Michigan to Los Angeles, Cal, with the obligatory stop in Colorado for the
Evergreen Jazz Festival at the end of July. Just before the trip, I
upgraded my homebrew 30M magloop to a new third-generation design. I increased
the loop circumference from 10' (3 meters) to 20' (6 meters; i.e. from a
diameter of 3.2 feet (.93 meters) to 6.4 feet (1.9 meters) and changed the
scheme for resonating the loop.
According to the KI6GD magloop calculator, I boosted the efficiency from about
35% of a full-size dipole to 68%; i.e. barely 1 dB down from a dipole. I set
my home station Kenwood TS-50 to do the APRS Messenger dual-mode alternate
beaconing on MFSK16 and AX.25 packet APRS before I left. [The latest revision
of APRS Messenger now makes it trivially simple to beacon alternately on the
two modes using the UZ7HO Soundmodem for the packet side.]
This has been an absolutely lousy ratty solar max compared to the solar max
around 2001-2004, where I routinely carried out perfect SSTV two-ways from the
car to Japan, Australia, New Zealand & South America. During the solar minimum
4-6 years ago, I routinely carried out APRS Messenger PSK63 QSOs from the car
to almost anywhere in the US 18 hours a day or more. I could make contacts from
the mobile in downtown Los Angeles or Las Vegas to stations in Kentucky and
Thunder Bay, Ontario pretty much any time I wanted.
This summer, the absolutely non-stop sequence of solar explosions, coronal
mass ejections, geo-magnetic disturbances, high solar "A" and "K" indices, and
exceptionally flaky sun spot behavior combined to render this positively the
worst summer I have ever experienced for HF mobile operation in over 25 years
of making this trip.
Usually, I run mobile live SSTV (from the WA8LMF "Mobile SSTV LiveCAM"
dash-mounted camera) on 20 and 15 meters on this summer trip, especially as I
cross the scenic parts of Colorado and Utah. In between SSTV sessions, I
beacon constantly on 30M APRS with both the APRS Messenger MFSK16 mode, and on
classic AX.25 packet APRS. During the the 6300-mile (10,000 KM) trip, I copied
exactly ONE SSTV image on 20 meters.
The 30M band sounded totally dead most of the time. I barely copied ANY AX.25
APRS at all, -BUT- the MFSK16 mode in APRS Messenger was absolutely amazing.
For the first 1000-1200 miles (1600-1900 KM) up to western Colorado, I was
copying my 50-watt home station transmissions from the magloop 18-20 hours a
day, even when the band otherwise sounded completely dead with no AX.25 signals
Even on the west coast in Los Angeles and the San Francisco Bay area, and in
the interior of Nevada, I was copying my home station 8-12 hours a day most of
the time, again on an otherwise completely dead band. This is a distance of
around 2000 miles (3200 KM) under absolutely rotten propagation conditions.
Repeated checks at WiFi hotspots from my mobile laptop confirmed that about
half the packets from my mobile, that reached the Internet, were being igated
by my own home station in Michigan.
Once again, this has demonstrated the incredible superiority of MFSK16 over
conventional AX.25 packet on HF if you want to be seen from the remotest places.
Stephen H. Smith wa8lmf (at) aol.com
EchoLink: Node # 14400 [Think bottom of the 2-meter band]
Home Page: http://wa8lmf.net
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