Author: Flavio Gori ­




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.





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:
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:
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 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:

MacCro - Good Shareware Oscilloscope/Spectrum Analyzer:

MacRTA - Commercial- Precise Oscilloscope and Spectrum Analyzer:

Canary - Commercial - Very good Spectrogram created for Bioacoustics:

SoundView - a very good freeware:

Useful site to check new Macsoftware release:


The site devoted to "Spectrogram", just for PC: