[CrossCountryWireless] Results of 60 Meters APRS Experiments #automation
Jef - N5JEF
I thought this well worth sharing. Very successful experiments with APRS via 60 meters mobile NVIS.
- Jef N5JEF #nvis #aprs
---------- Forwarded message ----------
From: WA8LMF via Groups.Io <firstname.lastname@example.org>
Date: Wed, Aug 22, 2018 at 11:01 AM
Subject: [CrossCountryWireless] Results of 60 Meters APRS Experiments
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
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
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
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
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