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glfer.1
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glfer.1
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.TH GLFER 1 "January 2010" "Version 0.4.2"
.SH NAME
glfer \- spectrogram display and QRSS keyer
.SH SYNOPSIS
.B glfer
[\fIOPTIONS\fR] ...
.SH DESCRIPTION
.B glfer
is a program that displays the power spectrum of a signal as a function of time
in a format known as a waterfall display; this is also called a
.B spectrogram.
The horizontal axis represents time. The time scale depends on the sample rate
and the number of points per FFT.
The vertical axis represents frequency, from DC to the Nyquist frequency
(half the sample rate).
The estimated power of the input signal is indicated by the color;
the spectrogram window has an automatic gain control (AGC) that
ensures always the maximum visual contrast and which, in
the current version, cannot be disabled.
.PP
Resizing the main window in the horizontal direction just changes
the length of the time scale; resizing it in the vertical direction
enlarges the portion of spectrum shown in the window. The entire
spectrum can be seen by scrolling the spectrogram window using the
scrollbar on the right.
Moving the mouse pointer on the spectrogram window shows the frequency
corresponding to the pointer position and the signal power at that
frequency on the status line at the bottom.
.PP
The first time glfer is run it will ask to select a control
port (serial or parallel) for the TX keying functions; if the mouse is
connected to the serial port be sure NOT to select its serial port for
controlling the TX otherwise the system may hang.
All the settings can be saved to a configuration file; in
this case they will be automatically loaded when glfer is launched.
.PP
Please note that the program must be run as root (or suid
root) to gain access to the transmitter control (parallel or serial)
port.
.PP
You may have to use a separate mixer program to
adjust the input volume and to enable the desired input.
.SH SPECTRAL ESTIMATORS
\fIglfer\fR can use several different spectral estimators to compute
the input signal power spectrum:
.SS Periodogram
the "classical" periodogram, which is obtained as the squared amplitude of
the discrete Fourier transform, after tapering the data with a
"window function" selectable among the Hanning, Blackman, Gaussian,
Welch, Bartlett, Rectangular, Hamming and Kaiser types. As usual,
the FFT number of points and the overlap between data blocks can be
freely changed.
.SS Multitaper method
The multitaper method is a weighted combination of periodograms
computed with different windows, all belonging to the same family and
having certain peculiar properties.
.PP
This method was described by David J. Thomson in "Spectrum
Estimation and Harmonic Analysis", Proc. IEEE, vol.70, Sep. 1982.
Besides the FFT size and overlap, it is possible to change also a
relative bandwidth parameter and the number of windows to use for
the analysis.
.PP
This method requires more CPU power than the first one, due to the
fact that several FFTs are performed on the same block of data,
using different windows. The resulting spectrum is similar to a
classical periodogram, but with much less variance (i.e. less
variation in the background noise [speckle]). Performances are also
similar to the periodogram, maybe it makes detection of QRSS
signals a little easier, but this doesn't means they are always
more readable.
.SS High performance ARMA
The (so called) "high performance" ARMA model assumes that the
input signal is composed only of white noise plus a certain number of
sinusoids and tries to extract the relevant parameters (sinusoids
frequency and strenght) from the data.
.PP
Reference article for this implementation is "Spectral An
Overdetermined Rational Model Equation Approach", by James
A. Cadzow, Proc. IEEE, vol.70, Sep. 1982.
.PP
At present this method is still experimental. There are two
parameters that can be varied: t is the number of samples used for
computing the samples autocorrelation and p_e is the order of the
AR model. This latter must be less than t, and both number should
be fairly small in order not to overload the CPU. The number of
sinusoids is estimated autimatically from the samples autocorrelation.
Use the default numbers as a starting point and experiment!
Unfortunately this spectral estimator performs poorly with
non-white noise (as we have usually in the RX audio, due to the IF
filters) and high noise levels. On the other hand it provides a
very good visual SNR with signals not buried in the noise
.SS LMP
This method is experimental
.SH OPTIONS
.TP
.B "\-d, \-\-device FILE\"
use \fIFILE\fR as audio device
(default: /dev/dsp)
.TP
.B "\-f, \-\-file FILENAME"
take audio input from \fIFILENAME\fR (WAV format)
.TP
.B "\-s, \-\-sample_rate RATE"
set audio sample rate to \fIRATE\fR Hertz
(default: 8000)
.TP
.B "\-n\ N\"
number of points per FFT to N (preferably a power of 2, default: 1024)
.TP
.B "\-h, \-\-help"
print the help
.TP
.B "\-v, \-\-version"
display the version of glfer and exit
.SH FILES
.TP
.B "~/.glferrc"
User startup file.
.SH BUGS
There was some report of problems in the audio acquisition routine, it
seems that some audio card/driver don't work well with \fIselect\fR; this
needs further investigation
.SH TODO
Maybe the Spectrogram should scroll as in other programs, all the
picture moving right to left
.PP
Jason decoder (in progress)
.PP
Spectrogram speed independent of FFT size
.SH VERSION INFORMATION
This man page documents
.IR glfer ,
version 0.4.2
.SH AUTHOR
glfer was written by
Claudio Girardi <[email protected]>
.SH "REPORTING BUGS"
You are welcome to send bug reports to Claudio Girardi
<[email protected]>. It would be helpful to include with the bug
description also the output of the \fIconfigure\fR script.
.SH COPYRIGHT
Copyright \(co 2010 Claudio Girardi <[email protected]>
.PP
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.
.PP
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
.PP
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
.br