Author: Flavio Gori
email: gori@mail630.gsfc.nasa.gov
Abstract.
Si propone lo studio e la realizzazione di un software tecnico
per computer Macintosh, in grado di simulare Oscilloscopio, Analizzatore
di Spettro e Spettrogramma/Sonogramma (tempo su frequenza), in
grado di adattarsi alle necessità specifiche dei Ricercatori
nel campo delle basse lunghezze d'onda del campo radio, al di
sotto di 15 kHz. Tale proposta è aperta ai contributi di
tutti gli appassionati del settore, che sono caldamente invitati
a collaborare.
Al termine dell'articolo si propongono alcuni siti dedicati a
software simili a quanto da noi richiesto, per quanto non del
tutto adeguati, già esistenti.
A NATURAL RADIO MAC-SOFTWARE PROJECT.
Why:
In the radio waves field, as happen in many other research
fields, hardware instruments are as important as expensive. In
the past years only professional laboratories could afford them.
Later some Spectrum Analyzer and Oscilloscope were available for
a restricted team of ham. Finally computer became so powerful
permitting software developers to design programs able to resemble
powerful hardware though extremely cheaper in front of hardware
instruments. This is not to say that software is cheap, of course,
only to say that is cheaper in front of those hardware tools.
So hardware and software have to become cheaper, but this is well
known, beside to be another story.
Around 1996/97 computer became powerful enough to run powerful
technical software. Not in every situation software have enough
power to run good instruments and usually Spectrogram/Sonogram
(sound in the time/frequency domain) need large memory space beside
strong power to run software and let user be aware about what
is going on in real time.
If CD, external hard disk, DVD or tapes, or any other means can
be easy to use for a professional team research, for amateur people
involved in this field, can become a hard problem to solve. Especially
in the VLF/ULF fields, a Spectrogram/Sonogram is, I believe, the
perfect tool to understand what is going on in a frequency group
where many things have to be found. This mean that probably the
perfect tool have to show everything appear in those long frequency:
just a Spectrogram/Sonogram can do.
This, unfortunately, means that we need so many memory space to
store it, unless you can find a system to start software when
"the" signal you are looking for may appear. I believe
that sometime an unexpected signal may be extremely important
and a not triggered threshold could lose it.
This article should serve as a first step to create a good
kind of discussion, as well as propositive, between Inspire members
involved in Natural Radio emissions, below 15 kHz until 0.01 Hz.
I am sure that all of you know very well what a perfect software
tool may have, to meet our need. Probably we need Oscilloscope,
Spectrum Analyzer and Spectrogram/Sonogram.
Maybe all inside a unique package, or in different instrument.
These tools already exists, of course, though designed for different
fields of use and very seldom they can meet our Natural Radio
need at all. We have to underline that one software exists created
just for VLF and below: it is "Spectrogram" for
PC. Please take a look there to understand many features our software
have to have, though it also lacks something important.
In my three years long research through the Internet it never
happen that one software works at all for what I need.
So I'll begin this first step, hoping that all of you may give
his ideas to understand what the perfect software have to be.
My ideal package:
What I am thinking about is a package-software-instruments including three tools as a Digital Scope Oscilloscope - who let me monitor 24 hours a day but record only when a given threshold amplitude noise is passed for "n" time. In this situation the record will start from the very first moment the noise began. If we have a recording session, the scope will monitor the condition one time every (for example) minute. If the noise amplitude is still on, the scope will record the situation, writing the UTC time of the measurement. When it find changed and the amplitude came back below the threshold, it will write the changing situation, its hour and minute, stopping recording. Of course the same have to do when the amplitude go lower than expected.
A Spectrum Analyzer should allow saving in automatic
just when a signal arrive, or when signal go over a given threshold,
savings memory on hard disk and work to the observer. Again, the
S.A. should allow to use all the base of the computer display
as the software allows monitor a large amount of frequency. It
will be wonderful monitor a wide frequency range, say until 30-50
kHz, if we want.
If and when we might be able to resolve the memory space problem
(where to store a big amount of data) we should consider a Sonogram
(time vs. frequency) software. I am sure it can be considered
as "The perfect tool" to understand a frequency range,
especially (but not only) a range not fully understand at all.
No other instrument can supply more data and in so good shape,
in my opinion. We could think something like the follow.
The Spectrogram/Sonogram capability as SoundEdit
(unfortunately SoundEdit is no more developed by MacroMedia,
and I don't know who is working on it now, if someone is doing
that please let me know. You can click on the Inspire Project
Home Page: http://image.gsfc.nasa.gov/poetry/inspire/
for better understand, in the VLF signals site)
would be a must, though a software for us should allow the logarithmic
scale too and very well done. Moreover we need to control
in the ULF realm, say as low as 0.01 Hz with a perfect resolution,
choosing the bandwidth to work/record, as well as to write about
7-10 notes-bars in every sonogram page, for future memory. One
more must has to be the real time sonogram making: hear
and see in the same time, in real time. One more plus: in every
sonogram page its important the time scale (as hh:mm:ss, in GMT
or in any other time we like set, as the time of our Mac) to better
resolve the time of the various signals we see on the sonogram,
also to correlate them with other recording from other sides of
the world.
The VLF radio range has to fight with the strong 50 (or 60) Hz
noise. A hard problem to solve, especially for who lives in the
so-called modern town, worldwide. In the last years some people
has become to think how get better with this trouble. One way
to try, would be to design a solution in two steps: one hardware,
designing an interface notch filter, able to catch the noise and
its harmonics, filtering all the way, reducing this strong noise
for about 70-80%. The other part of the noise should be cut off
by a similar filtering by software, to be enclosed in our package.
Another kind of need is related to record for many hours, the
only way to get around high quantity of data. Only large mass
of data would allow us to detect the ones we need to extrapolate
anything useful.
This will be possible only when we could establish a station receiving
at home, and this will be when a noise canceler will work ok.
On the other side many of us would want record other kind of signal,
manmade or natural, in VLF radio frequencies, say no more than
40 KHz, as well as lower, say until 00.1 Hz. In the last one field,
we need a carefully recording tool, able to catch any kind of
signal may be around. What can be heard and what cannot be heard
by human ear. What can be create in "normal time "and
what need longer time, as a slowing varying signal, or field.
The sonogram capability should supply invaluable help. I believe
that this kind of "noise" might be extremely useful
to find also, if not especially, in the ULF side.
In these fields we don't need to record and display in real time
the incoming signals, though a Spectrogram software is still needed.
This may be considered a strong field of future research searching
for unheard signals.
One good promising research in the field may also be the noise
floor of a given place. A Spectrum Analyzer may be considered
the perfect instrument to understand the local situation without
burn too much disk space. This could be used beside the Spectrogram:
while Sonogram monitor every signal, Spectrum Analyzer can tell
us when and how the noise floor may vary. The recording system
to monitor noise, might be the one said about the threshold.
If we are looking for just a way to understand if, when and how
a local noise floor works, we may do as follow.
Say that we might record 24 hours a day but display just a signal/noise
ratio average every "n" minutes, in order to create
a display for the 24 hours, every day. After 30 days the computer
and the software will calculate an average to create one month
situation made by the 30 days averaging.
In the same system we could calculate the year averaged, from
the monthly base averaged.
An important and simple plus will be the computer-video capability
to split in two parts (up and down) the recorded files, to let
us compare two same date recording the same frequency, in different
years.
I' d like that at least two of these software instruments should
work in the same time, getting a real time comparing with a cross
reference, an important way to compare a research.
One fine utility would allow the Mac to start up the recording
session at the time we'll choose, and stop after "n"
time. Probably will be important do not start down the Mac: many
switches on/off could do a negative work over the inside parts.
What should be included is a "Timer" plug-in,
so we could start and stop our recording sessions as many times
as we want, scheduling for a night, a week or one month in a very
simple and useful way. We should leave home/lab for sea or mountains
with no pain. Better than ever if we'll be able to establish a
net connection. From our vacation site we could monitor the virtual
site lab, realizing what is going on.
The Bottom line:
So, the tool I think we need is a Spectrogram-Oscilloscope-Spectrum
Analyzer absolutely designed for VLF/ULF radio range. While
Oscilloscope and Spectrum Analyzer have to have
good trigger and Timer capability as well as the recording system
already described for long time recording session, Spectrogram,
in particular, has to be able to work in real time, with log scale
from 15 kHz down to 0.01 Hz, resembling SoundEdit as well
as Spectrogram; can directly record in the hard disk both
audio and graphics with no limitation beside the hard disk space
and can provide a bandwidth to choose, from 0.1 Hz to 15 kHz,
permitting to write some notes below each sonogram for future
reference.
A PowerBook with that software, a good ground, antenna and the
Inspire VLF receiver may be the standard portable receiving station
able to digitize immediately the session avoiding any loss from
A/D converting (tape to disk) and great saving time.
E mail me:
I strongly ask to every Mac user who would like use this package
software to drop me a line at this address: gori@mail630.gsfc.nasa.gov
Of course, and I'll say again, I'm asking you for additions/corrections
to the requirements earlier said. Opinions from all of you may
be extremely useful to develop the right software for Natural
Radio researchers.
Later, when I'll know which kind of product we want, I will ask
to some Mac software developers about the possibility to produce
such a tool, how much this software would cost for each person,
in a shareware way, keeping Inspire members informed about the
entire situation.
A product like this could be extremely useful for the scientific
Mac community worldwide, showing, one more time, that Mac can
do a very good job in all the fields. I ask you to inform as many
ham as you can about this project, to understand the real amount
of people who may be involved. This can supply important information
for the real base of users: everyone interested in the Project
please drop me a line to let me understand how many people are
in "the MacGroup".
So write me your ideas, your suggestions, what do you think a
good VLF/ULF software has to be for your need. No one can say
it better than you: people who go in the field, the Inspire(d)
people. Inspire Journal and LoScrittoio.it will publish your suggestions.
All together may produce "the" software we want.
Good links to realizing what is around:
MacTheScope Commercial package software,
unfortunately cannot record long time audio file in the Spectrogram
mode, many other features useful for us:
http://www.channld.com/software.html#anchor326873
MacCro - Good Shareware Oscilloscope/Spectrum Analyzer:
http://pderrin.cjb.net/maccro.html
MacRTA - Commercial- Precise Oscilloscope and Spectrum
Analyzer:
http://exo.com/~vesphd/MacSLMPage8.HTML
Canary - Commercial - Very good Spectrogram created
for Bioacoustics:
http://www.birds.cornell.edu/BRP/CanaryInfo.html
SoundView - a very good freeware:
http://www.physics.swri.edu/SoundView/SoundView.html
Useful site to check new Macsoftware release:
http://www.versiontracker.com/
The site devoted to "Spectrogram", just for
PC:
http://www.monumental.com/rshorne/gram.html