[aprssig] APRS on HF

Sun Feb 20 10:00:25 EST 2011

I don't believe the picture Stephen has painted of VHF infrastructure in the
west is as bleak as he indicates. I concur there are still some secondary
areas (off the primary lines of communication) where there is "less"
infrastructure, but for the most part I would say there is generally good
coverage for our half of the USA and Canada.

My primary summer mode of transportation is motorcycle, and my little TH-D7A
in the saddle bag seems to do just fine on the roads my motorcycle likes
best of all, anything that is NOT a freeway. If I'm really in our lovely
wilderness and not getting any signals into the system for another 30-45
minutes, who cares? But for the most part I can ride around most places in
the west and manage a regular flow of burps into the system. The Snake River
in Idaho is pretty well covered giving the immensity of the nearby
mountains, and the expanse of central Nevada is extremely well covered by a
few remote mountaintop digis. If you've traveled the "Loneliest Road in
America" across Nevada you'll know what I mean. APRS coverage there was
spectacular and it was eerie not seeing another car on the road for as far
as the eyes could see. Further north into Canada, Banff and Lake Louise have
spotted coverage for some incredible terrain, and the folks around remote
Prince George in BC, where there are few users have a great network of
digipeaters. Back south, I've always been impressed with New Mexico. Back in
the early days of APRS, the group there converted about 15 digis from an
under-utilized packet network to APRS over a few month period, and again,
many digis, few users, excellent coverage. Overall I think we have good to
excellent coverage in western areas where our APRS users live, work, and
play. My problem areas are the density metropolitan cities where there is so
much traffic you can't get a signal in edgewise and everybody increases
power and adjusts tx rates to every 30 seconds just to be tracked. Give me
the lonely expanse and limited-to-good coverage any day of the week.

As a long time user of APRS, since the mid-90s when I used to dial-up Bob's
modem and download the latest version of APRSdos, which typically took 45
minutes and drew an evil look from the wife when the phone bill came. We
were in Texas at the time, there were few digipeaters out west and soon as
you got 50 miles away from any metropolitan region the airwaves were silent.
HF APRS was popular, and fulfilled the gap resulting from lack of VHF
infrastructure. Anybody remember when Pete used to drive his big rig along
I-10/I-20 back and forth from Florida to California and tracking on 10.151?
HF APRS across most of America now has little to no relevancy and because of
that I don't operate HF APRS anymore, even here at the house. The 706 in the
car is configured for it, but unused except for voice HF. There is still the
need for HF APRS as it applies to maritime use or those very remote regions,
such as the Yukon and NWT, although we do have VHF in Yellowknife, NWT in
case anybody stops by.

For the most part I think we have VHF infrastructure where we want, and need
it. If I had the fixins for about 25 digipeaters we'd fill the gaps across
the west where I think we need them the most. That's not bad, IMHO.

I concur with Stephen's other remarks, but 600 miles out of a 2200 mile trip
is not bad, since that 600 miles is interspersed, not all at once, along the
route. I would bet there may have been similar lack of cell phone coverage
along those same sections of the path. After a trip somewhere I'll usually
check aprs.fi and see how well I got into the system. There are generally no
surprises. Areas where there are "people" have coverage, areas where there
were no/fewer people had less or no coverage, but a little further down the
road and the coverage resumed. It isn't "bad enough" to warrant having HF
APRS to supplement VHF APRS along for the trip. When VHF APRS drops off, I
go down the road, and it picks up again. There's nothing critical to me
about maintaining a constant track in the system, or to let others know
where I am all the time. To the best of my knowledge we have few if any
incidences where there was some emergency and tried APRS and it didn't work.
Sure, that's likely to happen in the wilderness after someone's fallen down
a cliff, but the purpose of APRS infrastructure hasn't been focused on
including these kinds of incidents.

David K7GPS
Spokane, 300 miles from the coast

Message: 20
Date: Sun, 20 Feb 2011 03:30:35 -0800
From: "Stephen H. Smith" <wa8lmf2 at aol.com>
Subject: Re: [aprssig] APRS on HF
To: TAPR APRS Mailing List <aprssig at tapr.org>

Support of mobiles in remote locations has been the main use of HF APRS in
North America.

In the American west (and all of Canada more than 100 miles/160KM north of
the
US border), the population density is EXTREMELY LOW and VHF infrastructure
very
sparse.    In the US alone, this is an area approximately ONE THOUSAND MILES
SQUARE (1600 KM square) in the western one-third of the country.    (Once
you
go more than about 100 miles east in from the Pacific coast, coverage
shrinks
to almost nothing, except along the major Interstate highways and islands of
coverage in cities that are hundreds of miles apart.)

Turn off the Interstates onto the secondary roads and scenic byways in the
west, especially in mountainous terrain, and you drive off the edge of the
world APRS-wise on VHF.     HF coverage covers this mountainous Great Basin
area (the interior west between the Sierra Nevadas in California and the
Rocky
Mountains of Colorado) very well.    Depending on the time of day, you are
either propagating eastward to igates in the MidWest and/or the East Coast,
or
westwards to igates on the populous Pacific Coast, or both.

HF APRS is also widely used by pleasure boats in the Caribbean, and off the
west coast of the US and Mexico, once you get more than about 30 miles from
shore.   Given the very limited capacity of a 300 baud (or slower) channel,
and
the fact that every transmission occupies the channel for a radius of
500-2000
miles, depending on propagation,    absolutely the last thing thing you want
to
do is gate VHF traffic onto HF.

About twice a year I drive from Los Angeles, CA to East Lansing, MIchigan
(my
home town where my sister and mother still live) --- a trip of about 2200
miles/3500 KM each way. For about 600 miles of this trip there is just NO
VHF
coverage at all.

One-way igates break a major feature of  APRS operation:  two-way messaging.

I have carried on extensive two-way messaging from my mobile with the HF
APRS
Messenger application on the last three or four cross-country trips.   Most
contacts have been RF<-->RF, but I have had exchanges with a station in Los
Angeles coming out of an igate on the East Coast while I was mobile in the
southern Utah desert -- an RF haul of over 2000 miles.        The
effectiveness
of PSK63 over weak signal paths is dramatic when working from a mobile in
the
boondocks of the Great Basin.

-------------------------------------------------------------------------------

--

Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      WA8LMF  or 14400    [Think bottom of the 2M band]
Skype:        WA8LMF
Home Page:          http://wa8lmf.net
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