Stephen, You are a rock star of APRS usage and things to make us go Hmmmmm I wonder?? Thanks for documenting your travels and findings. KO4L Lloyd On Wed, Aug 22, 2018 at 2:01 PM, 'Stephen H. Smith' wa8lmf@... [ui-view] <ui-view@...> wrote:
For many decades now, long-range HF APRS operation has been done almost
exclusively on 30 meters. It will beam APRS posits over long distances
(2000
miles/3000 Km or more), but it does have a problem. At 10 MHz, there is
little to no NVIS (high angle) propagation. As a result, 30 meters has a
skip
zone of 250-300 miles (400-500 Km) most of the time. In other words, you
normally DON'T HEAR stations closer than this on 30M.
For some time now, I have felt that NVIS (Near-Vertical Incidence Skywave)
propagation (high take-off angles that will bounce signals back to earth
close
to the originating station (but on the other sides of mountains) would be
useful in large areas of the Great Basin/inter-mountain west. During
numerous
trips between Los Angeles and the mid-west over the past several decades,
I
have frequently noted the difficulty in being heard out of deep canyons
and
from secondary roads on the other side of mountain ridge lines from major
Interstate highways.
Propagation on 60 meters is almost the exact opposite of 30 meters in this
respect. 60 meters does NVIS propagation very well, and will provide
coverage
from 0 to 300 miles (500 Km) most of the day quite consistently. This
summer,
I tested the potential of 60 for APRS applications on two road trips. The
first was from my QTH in central Michigan (East Lansing) to Rice Lake,
Wisconsin about 400 miles (640 Km) to the northwest. The other was the
annual 1100 mile (1700 Km) trek to the Evergreen (Colorado) Jazz Festival.
The mobile setup was a Yaesu FT-891 transceiver running into a MFJ
monoband
whip for 60M (that appears to be a rebranded HamStick) mounted on a
split-ball
body mount on the left-rear part of the body of my 2006 Jetta TDI. The
transmit
power was about 15 watts. [I could have run the FT-891 at a full 100
watts
output.. However, since the 60-meter channels are shared ham/non-ham use,
I
wanted to keep the ERP low enough that others could talk over my beacons
if
necessary.]
The APRS application running on the mobile Panasonic Toughbook was G4HYG's
"APRS Messenger". This soundcard modem application can function as a
mobile
tracker, beaconing alternately on 300-baud classic AX.25 HF packet, and on
MFSK16. Messenger's MFSK mode actually sends the payload of an APRS-style
AX.25
packet, including the packet-style path headers and checksum at the end,
over
MFSK16. For an additional comparison, I had a TinyTrack 3 set for HF
300-baud mode and MIc-E format to evaluate the relative effectiveness of
the
longer plain-text posits sent by Messenger and the shorter Mic-e packets
sent
by the TinyTrack. The callsigns were WA8LMF-6 for the AX.25 mode,
WA8LMF-66
for the MFSK mode and WA8LMF-2 for the TinyTrack Mic-E beacons. [I was
also
beaconing WA8LMF (no SSID) on conventional 144.39 two-meters APRS with my
Kenwood D700.]
The fixed station/igate at my East Lansing QTH was a Yaesu FT-857D
connected to
a 105' (32 meter) center-fed dipole fed by 450-ohm ladder line and an Icom
AH-2
auto-coupler. The software was identical to the mobile (APRS Messenger and
UIview) running on an Acer E3-111 "netbook" mini-laptop that runs Win 7 on
a
dual-core Pentium 4. [I like these mini-laptops for APRS applications,
where
you leave computers running 24/7 for weeks at a time, because they consume
only
9-10 watts.] I also had the TightVNC remote control program running on
the
Acer so I could view the machine's screen and and tweak settings remotely
while
on the road. The beacons successfully found their way to findu.com and
APRS.fi, courtesy of my igate.
These tests took place on US "Channel 5" of the fixed-frequency
channelized
60-meter band. This is 5403.5 KHz USB. Partly because it is the shortest
wavelength channel on 60M so the mobile whip is the "least inefficient".
And
partly because by informal convention, "Channel 5" is the "data channel"
on
60. [There is no segregation between voice and non-voice modes on 60 as
there
is on the other HF bands. You can legally use any mode on any of the 5
channels.]
__________________________________________________________
The results more than met my expectations. The trip to Rice Lake, WI was a
loop
- outbound "over the top" of Lake Michigan via Michigan's Upper Peninsula,
while the return was via Madison WI and Chicago around the "bottom" of
Lake
Michigan. The 60-meter coverage was essentially continuous. In remoter
parts
of the Michigan UP and north-eastern Wisconsin, where two meters heard
nothing,
the 60-meter posits just kept coming in.
Another variable comes into play. Propagation on 60M does change with the
time
of day and day vs night. On the outbound trip, the shortest hops from the
mobile to the igate were in daylight, starting at about 0800 EDT (local
time).
I arrived in Rice Lake (greatest distance) at about 2100 EDT; i.e. just
after
dusk. On the return trip, exactly the opposite with the longest hops in
the
AM daylight, and the shorter hops well after after dark as I approached
home.
The closer hops (under about 150 miles/240 Km) started failing on the
return
trip because it was now well after sunset; i.e. 2200 - 2400 hrs EDT.
The trip to Colorado was perhaps more interesting because 1) It was a
much
greater distance from home and 2) The route was much closer to being a
constant
latitude. [Since HF propagation is the result of the upper atmosphere
being
ionized by solar radiation and particles, and because those particles are
deflected by the earth's magnetic field, HF propagation effects are quite
sensitive to latitude north or south. By driving a nearly straight
east-west
line, one keeps at least one variable in the test more-or-less constant.]
After driving from central Michigan to Chicago and joining I-80, the rest
of
the trip was almost due west along I-80 to the Colorado border.
The 1100 mile trip from MI to Denver takes two days. The mid-point of the
trip
is at the west side of Des Moines, Iowa, where I always spend the first
night
about 550 miles (880 Km) from home. All along the route, I would
periodically
stop to connect to WiFi at gas stations and fast-food joints to check my
own
UI-Webserver via VNC and APRS.fi to see if I was reaching my solitary
60-meter
igate in Michigan. [The ultimate convenience is in Iowa,, where every
rest
area on the Interstate has free WiFi beamed into the parking lot from a 9'
fiberglass 2.4 GHz collinear whip on top of the building. You can easily
get
WiFi from a laptop inside your parked car.]
I had expected that the signal would start dropping out at 300-400 miles (
500-650 Km) from home, but I had constant coverage on 60M for the entire
day's
drive.. To my surprise, the signals were still booming into my Michigan
igate
when I arrived in Des Moines at about 1900 hrs EDT. After check-in, I
left the
gear running in the parked car, while I played with the Internet in my
motel
room. [I have 110 AH of sealed AGM batteries in the trunk of the car,
isolated
from the starting battery, so I can safely leave electronics on for many
hours
after engine-off.] The Michigan igate's reception started failing about
2300
hrs EDT. (At this point I was in US Central time where it was 2200 hrs
local.)
Most striking, I noticed the AX.25 beacons starting to fail about 45
minutes
earlier than the MFSK16 ones. It dramatically demonstrated the enormous
superiority (10-15 dB advantage) of MFSK16 over classic two-tone FSK
300-baud
packet under weak-signal conditions.
I had assumed that I would be out of range of my home station on 60 meters
well
before the end of the first day, and had intended to switch the mobile
setup to
30 meters that evening, for the rest of the trip. (I had an identical
HamStick
for 30 meters stowed in the car.) Instead, I kept the setup on 60 meters
the
morning of the second day. When I departed after breakfast at 0900 hrs
EDT
(0800 local), no beacons were being heard by my Michigan igate. By the
time I
stopped at another Iowa WiFi rest stop about an hour down the road, in the
Avoca, Iowa area, the MFSK beacons were coming in again. By the time I
arrived
in the Omaha, Nebraska area, the AX.25 FSK beacons were coming in also.
Both
formats continued to be received until I reached the Lincoln, NE area,
about an
hour west of Omaha. At this point, I did switch to 30 meters.
On the return trip, the last night on the road was in Avoca, Iowa where I
switched from 30 meters back to 60. Again, I saw no evidence of my beacons
reaching my igate in the morning until about 0090 hrs local (1000 hrs
EDT). .
Again, the MFSK16 beacons "opened the band" with the AX.25 ones starting
to
appear about an hour later.
_________________________________________________________
The final conclusions are: 1) 60 meters CAN provide quite consistent
APRS
coverage from 0 to 400 miles (640 Km) or so. 2) The MFSK mode has a
huge
advantage over classic 300-baud FSK, providing nearly two more hours a day
of
usable progation. Sometime this fall, I will be making a trip EASTWARD
on
I-80 crossing the Appalachian Mountains to Philadelphia. This will be an
opportunity to try NVIS propagation out of some smallish valleys in the
eastern
mountains. Ultimately, I would like to try absolutely maximizing the
NVIS
receive performance by building a turnstile antenna consisting of two
60-meter
dipoles crossed, supported as inverted-Vs on the same mast, and fed in
quadrature with coax phasing lines. Stay tuned!
__________________________________________________________
Stephen H. Smith wa8lmf (at) aol.com
Skype: WA8LMF
EchoLink: Node # 14400 [Think bottom of the 2-meter band]
Home Page:
Live Off-The-Air APRS Activity Maps
<>
Long-Range APRS on 30 Meters HF
<>
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Lloyd KO4L