ARLA/CLUSTER: PSKmail, a historia de um projeto.

[João Costa > CT1FBF]

The history of the project

The PSKmail project was started by Rein Couperus, PA0R early 2005. The
baby  steps were taken with a modification of gMFSK, the mode of
choice was PSK63 and  traffic was handled by the one and only server
(PI4TUE) that existed. Soon another server joined the effort, SM0RWO
in Stockholm, and suddenly the project had “multiple” users (two) and
had to evolve. For a time there was only the server in Stockholm and
two clients (PA0R and SM0RWO) and the project made necessary
adjustments for the hf environment. Soon more servers started to
appear, IS0GRB/Roberto, added a much needed server in the
Mediterranean.

Then more and more servers joined, such as WB5CON/Fred and
DL9YCS/Jörg. The Intermar group then followed with several servers. At
the start only email traffic was handled and, as stated earlier, only
done so using PSK63. Soon more services were added, web browsing was
one of those. One of the more important additions was APRS.

Traffic was handled nicely by PSK63 but yours truly, SM0RWO, felt the
need for speed and noticed that the Fldigi project offered PSK125.
Quickly Fldigi was integrated and PSK125 was the mode of choice for a
long time. That urge for faster modes resulted in a move to PSK250
which is an excellent mode, it is of course faster and thus wider (abt
250 Hz). Wait a second, we almost always use 500 Hz filters in our
rigs. Why not aim for a 500 Hz wide mode then? That mode was PSK500
and we moved there around summer of 2009. Lengthy discussions within
the group resulted in the consensus that it was time to break free
from the chains of the old PSK31 keyboard to keyboard concept.

PSK31 was indeed a fine idea but it had to make some sacrifices in
order to reach its goal of being a suitable successor to rtty.
Processing times could not be long, it had to deliver data pretty much
in a similar way that the rtty operators were used to and one apparent
problem was a lack of forward error control. A missing character here
and there can mostly be handled by the human brain, not so by a
computer with checksum control of received frames.
VK2ETA, John Douyere, made it his task to create the more robust modes
where FEC and an interleaver net was added to the PSK modes, the new
mode is designated as PSKRobust 500/250/125 and has been a real
success.

In fact PSK robust 500 has been the default EU mode ever since. Mode
profiles were added by Rein, these control the server speed and mode
that can be adapted by the server. The server can move a connected
session to a faster mode when the conditions are right and can of
course select a more robust mode when the conditions deteriorate.
While writing this asymmetric linkup has been implemented. By that we
refer to a connection that does not use the same mode and speed in
both directions. For instance its now possible to have a weak client
use a slow and robust mode while the server uses a very fast one. The
mode scope now ranges from THOR4 to PSK500,
using PSK, MFSK and THOR modes to cater for differing adverse conditions,
including polar flutter, multipath, Doppler and QRN.

Introduction
How much bandwidth does the mobile ham really need?
Like most questions, there are several answers to this. The best one probably
being “it depends on your lifestyle”. If you are used to broadband internet
access and don’t want to give that up when you are en route, you are a
potential candidate for internet access via satellite, and you will
have to bear the cost of that luxury. If on the other hand you are en
route to relax, and you don’t need instant information, you could try
PSKmail for bare bones information delivery.

Pskmail gives you a 500 Hz wide channel to the internet. This is
enough to get the most important email, the weather forecast and the
daily update on the sunspots. Being nomadic, we live on a boat during
summer and in a camper during winter, I get by with 200 Hz and a half
hour session with the server most of the time. How much email do you
really need daily to keep up to date?

Of course we combine daily PSKmail with a webmail session once a week,
to get the ‘picture ‘ if you know what I mean. And to get the non-ham
stuff.
But I can upload software patches to the internet on a daily basis while living
on a Mediterranean beach which does not have a ADSL socket.

What is PSKMail?
PSKmail is a narrow band arq system for use by amateur radio hams via
short wave (HF) communication. It does not use a special controller,
you just need a
computer with a sound card.

The PSKmail server uses the fldigi program as a modem, and can use
PSK, MFSK and THOR modes, including the new robust PSK modes which
include soft viterbi decoding and interleave to increase immunity to
qrm and qrn. The client is written in java, and has the modems built
in. The operator can choose several modes and speeds when starting a
connection, to match channel conditions.

The main characteristics of PSKmail can be summed up as:
● A semi duplex ARQ Chat client capable of transferring files
● A full fledged solution for HF APRS, including integration with the map
clients
● An internet connection that can be used where there is no internet
connection.
Such as from a boat at sea or a cottage somewhere or on expedition or…
● Narrow, efficient, data modes are used. Thus enabling even the most modest
setup.
● Servers on short wave provide long range connectivity
● No expensive and bulky modem, all you need is a PC, a transceiver and an
antenna
● Available on multiple operating systems (Linux and Windows, MacOS and FreeBSD)

PSKmail Manual (PDF File)
http://pskmail.org/downloads/jpskmail_manual-1.5.7.pdf

PSKmail WiKi
http://pskmail.wikispaces.com/

PSKmail downloads
http://www.pskmail.org/PSKMaildownloads.html

Link
http://www.cqdx.ru/ham/new-equipment/pskmail/

Fonte: SPARKY’s Blog