[I am posting this on the list, instead
of an individual reply, because I think it may be of general
interest to other users.]
On 12/28/2024 1:35 PM, Todd AL7PX via
groups.io wrote:
I am interested in using and joining this mode of operation
but fail to fully understand the basics of operation.
I have used and currently have installed Winlink RMS client
software and have completely operational. I access my local RMS
VARA high speed Vara FM and also use VarAC HF mode. I also have
have FLdigi latest version installed and using for sitorB
monitoring and other modes. Can someone please explain to me
what use does APRS
and fundamental operation use do (other than location) and
explain thoroughly give example of all software combined
actually do? How are messages sent? What SW are you using?
FLdigi? I like to utilize 30 meters but fail to find others who
use this band for much of any mode other than FT8, which I have
no interest in whatsoever.
APRS (the Automatic Packet Reporting System) was originally
conceived of by the late WB4APR (Bob Bruninga - an EE professor at
the US Naval Academy ), as an all-purpose system for distributing
information of interest to hams over the air. Unlike most digi
comms, APRS has no two-way hand-shaking logical "connection"
between stations. It uses the "unconnected information" a.k.a.
"UI-Frame" beacon mode of packet radio to send one-to-many
broadcast-style messages. [APRS was patterned on the
battle-field "situational awareness" messaging systems being
developed by the Army and Navy at the time.]
In addition to the well-known position reports from vehicles,
APRS is used to send reports from unattended weather stations,
announcements of events like ham fests and swaps, coordinate
search-and rescue efforts, etc. APRS can also exchange short
one-liner cellphone-style-SMS text messages between specific
callsigns, and even to/from internet email addresses.
For over 40 years, APRS has been conducted with 1200-baud VHF
packet and 300-baud HF packet on HF. The earliest use of APRS
was to report positions of boats in U.S. Naval Academy yacht races
on Chesapeake Bay in the 1970's.
Originally an exclusively RF-based activity, connections between
RF and the Internet were added to APRS in the mid 1980s. APRS
"igates" (Internet GATEways) can connect RF activities in areas
far too distant from each other to communicate directly on RF
alone. (This is similar to the Internet "worm holes" created by
EchoLink, DMR, Yaesu C4FM, D-Star etc.) It can also connect
people with radios to people with just an Internet connection,
such as a smart phone).
VHF packet-based APRS is done all over North America on the same
VHF channel -- 144.390 MHz. As a mobile, you drive into and out-of
the range of hundreds of base station "digipeaters" and "igates"
as you travel, each of which will automatically retransmit your
beacons and messages over the local area on RF -- and pass your
beacons to the "APRS-IS (APRS Internet System). The APRS-IS is a
inter-connected system of dozens of Internet servers and mapping
websites world-wide.
Traditionally, APRS was done with hardware radio modems a.k.a.
"TNCs" - "Terminal Node Controller". These would be connected via
an RS-232 serial port to a computer running APRS "client" software
for messaging and mapping position reports.
Today, APRS is overwhelmingly done with soundcard-based packet
"soft modems" like the "UZ7HO Soundmodem" or "DireWolf" linked via
TCP/IP to APRS client applications like "UIview" or "PinPoint
APRS". These "soft modems" use the same kind of "sound card
interface" as most other digi modes.
Note that APRS DOES NOT use software like WinLink, VarAC or
FLdigi -- APRS is a completely different activity that just
happens to be able to exploit the KISS-over-IP connection present
in the VARA modem software.
300-baud HF packet-based APRS has been used for over 4 decades at
the very top end of the 30-meter band for long-range APRS in
locations without 2-meter APRS coverage. The actual RF frequencies
of the two-tone 200-Hz-shift FSK transmissions are 10.149.200 MHz
& 10.149.400 MHz. Typically this is done by tuning the radio
to 10.147.600 MHz USB "dial frequency" which will yield the 1600 /
1800 Hz audio tones most classic hardware packet devices respond
to.
Classic AFSK-based 1200-baud packet radio works well on VHF-FM,
but classic packet is a HORRIBLE mode for HF. It
is absolutely intolerant to the QRM, noise, selective fading and
multipath distortion common on HF. There is no
forward-error-correction like most modern digimodes, often
requiring transmissions to be repeated over and over again to get
through.
In the last few years, far superior data-transmission modes for
HF use have appeared. The VARA soundcard soft modem is orders of
magnitude better at "getting through" than classic packet on HF.
With data wrapped in two layers of forward error correction, it
can provide error-free copy on signals so weak they can literally
cannot be heard in the radio speaker! On the other hand, with a
strong noise-free signal, it can automatically increase speed to
exceed the throughput of a 1200-baud VHF packet modem in a 500 Hz
CW bandwidth on HF.
For about two years now, I have been advocating using VARA for
APRS activity as a VASTLY superior replacement for classic
packet on HF. I have tested it for this purpose over 10s of
thousands of miles of mobile operating on 30 meters. I have
even done three-way shoot-outs comparing 300-baud-packet vs VARA
va FLdigi in MFSK16 mode on road trips. APRS-over-VARA is now
beginning to take off -- about a dozen stations around North
America are now active on the mode regularly. I am routinely
hearing and being heard by G4HYG in Scotland on the
APRS-over-VARA mode. Several stations are now running
APRS-over-VARA igates 24/7.
Because of VARA's incredible weak-signal capability, it is
practical for a mobile or RVer to be tracked and to communicate
almost anywhere with low power and modest antennas; i.e. Yaesu
FT-818 "porta-luggie" and a 30M HamStick-type whip or random wire.
During my 6300-mile round-trip from central Michigan to Los
Angeles and back this October, mu mobile was being heard and gated
to the Internet almost constantly using a FT-891 transceiver with
Quicksilver Radio "QuickStik" mobile whip connected to my mobile
Panasonic Toughbook mobile laptop. I had numerous two-way
messaging contacts over the same setup as well.
Stephen H. Smith wa8lmf (at) aol.com
Skype: WA8LMF
EchoLink: Node # 14400 [Think bottom of the 2-meter band]
Home Page:
30 Meter APRS-over VARA Frequency Change
Coming 1 Jan 2025. Details Here:
- APRS over VARA --
"Studio B" Ham Shack on Wheels
-
