Websdr
is web server software that allows many users to listen to different
parts of the radio spectrum over the web. It was written by
Pieter -Tjerk de Boer, PA3FWM. The
server at K7UEB is not only
available for users all over the world to listen to, and use for
experiments; it is also a robotic radio,
spotting
stations on the digital mode PSK31 (and maybe soon RTTY and PSK64).
Hardware
The hardware consists of a Dell GX620 with an M-Audio Delta 1010LT
96KHz audio card connected to three
Softrock
receivers. All three receivers are connected in parallel to a
Hustler
4BTV vertical on the roof. The hardware resides at the K7UEB
club station on the campus on
Walla
Walla University.
Presently, the 20 meter SSB receiver has very poor sensitivity,
and the 40 meter receiver has an intermittant problem with the
oscillator quitting. Maybe I'll get a chance to fix those
sometime.
Software
The heart of the robotic radio is the software. The software is
running on
Ubuntu
Linux version 10.04. Administration of the software is
accomplished remotely over
NX using
Google's
neatx
server which allows remote X sessions that can be connected to, and
reconnected to at will, from most any client computer connected to the
network.
Audio routing is handled by the
Jack
Audio Connection Kit, which allows the audio to be split and sent
to several different processes that each need it for their
purposes.
The
start
up script I use shows the detals of how all the software is
started, the options used, etc.
Websdr
Websdr uses
OSS
sound (/dev/dsp), but the developers of Jack firmly believe that OSS
should be depreciated, so there wasn't a good way to connect between
Jack and the Websdr server. Pieter suggested I could use named
pipes
to couple the output of Jack to the input of websdr, so I wrote
jack-fifo, a C program which does that.
It
is available under the
GPL license for you to examine or use too, if you wish.
There is a lot of QRN
from powerlines at the K7UEB QTH, so I added a noise blanker into
jack-fifo to try to remove the noise. It works pretty well, but
there
are still more improvements I want to try with the nosie blanker.
Spotting Robot
The spotting robot uses several pieces of software, and several
instances of all that software, for the different bands/modes that are
being spotted. Sound from Jack is sent to
sdr-core
(DttSP), which is the same DSP software that the Flex radios use.
The output of sdr-core is coupled to
Fldigi which demodulates
the digital signals and sends the spotting data to the
PSK Reporter web site, which
displays it on a map and in other ways.
Qustions:
Rob "dot" Frohne "at sign" wallawalla "dot" edu