PSK: Arcotel Farcos 1800 EADS/RACOMS psk-4, ALE

Arcotel Farcos 1800 EADS/RACOMS psk-4, ALE.

Author: SergUA6 6.0
Band Width ~2200-2400 Hz
Low Range 500-600 Hz
Baud Rate 1800 Hz
n-Ary PSK/MPSK PSK-4
Carrier frequency 1600 Hz is standard, in this example carrier frequency is 1648 Hz
RX mode SSB

The signal is here.

Sonograms:

pic.1 General view

pic.2 Speed

Pictures:
pic.3 Phase constellation

ARCOTEL FARCOS 1800 EADS/RACOMS - this signal is from the same series as ARCOTEL MAHRS 2400 EADS/RACOMS, but it has other PSK mode, a little bit shorter bursts and slower speed. The presence of header with psk-2 duration about 70 msec is characteristic.

PSK: Arcotel MAHRS 2400 EADS/RACOMS PSK-8, ALE

Arcotel MAHRS 2400 EADS/RACOMS
PSK-8, ALE

Author: SergUA6 6.0
Band Width ~2800-2900 Гц
Low Range 300-400 Гц
Baud Rate 2400 Гц
n-Ary PSK/MPSK PSK-8
Carrier frequency 1800 Гц
RX mode SSB

The signal is here

Sonograms:

pic.1 General view

pic.2 Manipulation speed

Pictures

pic.3 Phase constellation

ARCOTEL MAHRS 2400 EADS/RACOMS - It Sounds similar to one of LINK-11 variants, so it is possible to confuse these two signals.
At attentive studying it is visible that it is psk-8 serial. on such short signals it is difficult to receive the qualitative picture on the phase plane, but if to run whole file, that all is easily clarified. The presence of the short PSK-2 fragments in the begining of each pachcage with duration 60 m, is is typical.

SA updating to version 6.0.7.0

Version 6.0.7.0

In version 6.0.7.0 the number of radical updates is realized. One of the new feature is the ability of reffer as "read only" to resource, where the analyzed file is located.

All SA versions work only with a copy of the original record, it was made with the purpose to guarantee safity of original record, in case of force majeures. But, in old versions the copy had been created in the same place, where the original record was located. Thus, the direct work with the records, which are located on CD, flash disk or network resource was too slow or even impossible.

The problem is solved in the current update, now the copy is created in the own SA "Temp" directory.
Since, sometimes it is extremely desirable to see the full path to initial file, this path is specified in the Status Bar of the main window. The path to the initial file is specified for active window, or, for the window, over which the cursor is placed. In the working windows, the relative path to copies, with which SA works, is specified.

Another serious enough, but outwardly not very noticable changes:

• the algorithm of the graphics displaing/mapping in WF module is optimised: speed is increased in several times, lthought on the fast computers it may be not so noticable, but on the weak ones, especially in a fullscreen mode the difference is very essential.
• the operation/work of the semi-automatic corrector is optimised: the algorithm is refreshed. Earlier on the fragments, where the signal is absent the proofer simply stopped, now it is fixed. Precision of correction is increased.
• the various collisions which could be called by operations of user are removed. For example, earlier, in WF module or VMW the automatic increasing/reduction of the graphic's scale at moving of the cursor and pressed on mouse button at the same time, would led to uncontrolled process.
• some minor moments are solved.

Good luck.

MT-63 and some other non standard OFDM signals.

Non standard OFDM signals.

Being engaged into analysis of MT-63, there was found out several similar signals. As it has appeared, it is not such rarity. Before we will start to consider MT-63 in details, we will try to understand, basically, what are specifics and features of these signals .

Probably we wouldn't pay attention to this class of co -called pseudo OFDM signals, but examination of the developed module of the analysis of OFDM, has shown that there are signals, which are generated obviously not by standard technology, at least the analyzer is "slips" a little bit on the records, which quality seems to be exellent.

Besides, some discussions on our forum were linked to this question.

There are three signals which do not fit into the standard scheme of OFDM creation.

Probably, there is nothing unusual can be visible at once, but attempts to simulate Codan-16 by the standard technology do not lead to reception/getting of adequate model. The difference will be more obvious if to compare Codan-16 with Well-known CIS-12 tone, from the point of view of the main relations of space between channels and speed of manipulation, these signals have approximaly identical structure, and thus we can expect approximaly identical spectral allocations. However distinctions are very essential.

It is well visible that Codan-16 has too obvious almost complete partition of channels, while the classical methods do not provide it. CIS-12 tone has the typical result of the classical OFDM creation , and the overwhelming majority of cases OFDM signals look same.

It is known that, sometimes the difficult enought methods are used at creation of OFDM.
For exmaple the methods of :

• reducing of out-of-band radiations
• increasing of the spectral density
• reducing of the peak-factor

But all these methods are not used untill complete partition of the channels, besides all, these methods do not distort the signals to that point, then the reverse demodulation by the classical ways becomes impossible, on the contrary, these methods are aimed to provide compatibility.

An obvious conclusion - these signals are created by other way. It is not the big secret or strong innovation, but nevertheless, it can cause complexities at the analysis, and basically, it can even to lead to incorrect results of the analysis.

Signals, which are similar to DIGTRX and Codan-16 are formed by FDM technology. Let's not go deep into details, but in general, the sense of FDM technology is: that the prototype of the one channel with the obviously established form is created, and then on the basis of this prototype, the grid of working channels is formed.

Practically the spacing can be any, orthogonality is not necessary.

It allows to reach more density of usage of the spectrum, in comparison with the classical multi-channel (not OFDM) systems.

We consider the task of analysis, not only as definition of parametres of a signal for the purpose of its identification, but also with the purpose to understand what is necessary for the signal's demodulation.

In this sense, the conclusions for Codan-16 and DIGTRX that these signals are the classical OFDM signals certainly is not true. These signals do not have CP, which "is easily calculated" from the relations of speed and spacing, they have not orthogonal grid of frequencies, and it is impossible to demodulate these signals by the classical OFDM approaches. From the point of view of analysis there should not be vaguenesses in the signal at the analysis. It is necessary to know all features of the analyzed signal and understand why these features are placed in the signal. Ofcourse it is not always possible, but one of the main goals of analysis is the full detalization of the signal and it's nuances.

Let's come back now to MT-63. Principles of creation, which were described above, had no success in case with MT-63. The signal is obviously formed by the standard OFDM technology, but the result is not standard. Fast enough we have ascertain that the signal is divided/separated on two groups of the channels: even and odd. These groups have shift/displacement relatively each other on half-clock/tact of frequency of manipulation.

That is, as the variant, by the standard resources of OFDM technology, two independent streams of even channels and odd accordingly, are forming. CP is added in each stream, and both these streams are merged into one. It is possible to provide the shift/displacement on half-clock/tact both at creation of streams and at their merging, as the result we receive pseudo OFDM, where according to all signs/characteristics, it is classical OFDM, but all attempts to demodulate it by the standard for OFDM methods are failing.

It is not easy to get to know how it is possible to devide/separate these streams at reception/recieveing by simple methods. Ofcourse there are solutions, but it turns out difficult enough.

Besides, the sense of such creation is not really obvious, because there are no particular advantages before the classics methods, at least we had not found them.

That would be interesting to get to know: why is there the necessity of such shift/displacement of even and odd channels? And that it gives basically? Except doubtful reducing of the peak-factor and obvious, considerable complicating of the demodulator.

OFDM Signal: MSM-1250

MSM-1250
Thales "SkyFax", RC5000 series - Javelin

Author: SergUA6 6.0
Band Width ~2400-2500 Hrz
Low Range ~600 Hrz
Baud Rate 125 Hrz in the channel
Count of Carriers 10 channels FSK-2 with frequency spacing 125 Hz
Step between carriers 250 Hrz between centers of the channelers
RX mode SSB

The example of this signal is here.

Sonograms.

pic.1 General look

pic.2 Speed of manipulation

pic.3 Detalization

MSM-1250 - the signal is 100% generated with usage of OFDM technologies, and it do not getting under MFSK In Reallyty, there is no problems to form not only similar signals, but also any multistrip(multi-band) signals with usage IFFT, as becomes in practice in 99.99 % percent of cases.

Certainly, any of prefixes are not used here, because there is no necessity in it, since there are no problems
with synchronisation , owing to the selected sort of manipulation and synchronism of transactions on all channels.

Besides, the spectrum is used with not maximum density, as there are "holes" with width ~ 125hrz between
channels "holes" in width of 125 hertz, because of the selected sort of manipulation. Technical speed of the
whole stream is 125*10 = 1250 bps, as it is reflected in The name of the signal.

SA Update to version 6.0.6.7/8

SA Update to version 6.0.6.7/8
Quality detalization on the wideband signals.

SA Update to version 6.0.6.7/8

The main difference of this version from all previous versions, is the new algorithm of drawing/calculation of a spectrum in the window of mapping.

This problem, which we have solved, is known for a long time to us, but on relatively narrow-band signals it had no essential value.

Active SA usage for analysis of wideband signals and records, basically it is I/Q records from various complexes, has shown, that the risk to skip or not to notice features or the interesting moments, is great enough. The Current update reduce this risk almost to zero. Anyway, in this case, it is easier to show, than to tell what and how has varied and in what side.

The arrows show the places of essential differences(not all ofcourse). Especially I would like to mark that, this new drawing algorithm, solves wide number of problems everywhere, where the spectrum is displayed. Now all lines, details and the common nuances of record/signal will be displayed, independently of sonorgam's size.

In version 6.0.6.8:

• the algorithm of graphics drawing in Phase Plane module is changed
• the values of FFT block are synchronized with the window , from which this module is called/launched
• the mode of complete/full spectrum showing is turned ON by default
• the limit of loaded into SA files is increased to ~ 150 megabytes.

The various problems both small, and rather serious, are solved. These problems were detected by users and beta testers. In particular, in the previous version 6.0.6.7 two minor problems, were detected and solved.

Good luck!

p.s

Sometimes people ask us, why the versions folow each other not consistently?

In reality, all updates are always going throught iternal tests, and it is very often, that already at this stage of testing, the version "dies" before birth, and there is changing of the versions is happen. There is nothing unusual in it, it is usual process. Internal testing does not guarantee skip of errors.
We express huge gratitude to all users and beta-testers.

SA Update: version 6.0.6.4.

SA Update: Version 6.0.6.4
Reverse synthesis of FSK/MFSK signals.

New in version 6.0.6.4:

• the minor problems are solved
• some algorithms are optimised
• ability of reverse synthesis FSK/MFSK of signals is added

What is the reverse synthesis for? There is the certain problem with the signals, which have poor enought quality. If, in SA, it is possible to define parametres, and there is the possibility to save the signal in the better quality compare to initial one, then it is desirable to do it. We will consider a standard example.

The record Piccolo-12 from the site http://www.signals.taunus.de/FFT/PICC-MK12-TFC.jpg, by the way, is the only one record, which is managed to be found in Internet by me. It is well-visible, that the level of interferences is very high. Standardly used, in such cases, amplitude limiters do not make the situation better.

Nevertheless, SA allows to define paremeters of this signal reliebly enough, and moreover, SA allows to save the resulting signal in the much better quality.

Reverse synthesis removes both out-of-band noises and interferenсes and in-band ones, which are hardly can be removed by other tools. The difference is perceptible both by ear and by sonograms:

• initial signal
• restored signal

Reverse synthesis in SA, restores the signal in the same frequency positions, and with the same frequency spacing and speed of manipulation, as an initial signal.

There are more examples:

BulDiplo - is the high-speed enough signal.

On the record of Chinese modem MFSK-64 - almost complete suppression of noise is well visible.

Ofcourse, reverse Synthesis, as any other tool, has it's own field of application.

No need to use it too much and all the time, no need to expect that this tool will solve all the problems with the noisy records.

The positive accuracy and thoughtfulness is needed, some experience and skills are also required.

Attention please: Never represent similarly edited records for analysis.

Everywhere and always I insist that the analyst should have for the analysis completely initial, not touched (and not edited) material. Only the analysit solves what to do with this material and how to do
it.

Reverse synthesis is the tool of analysis, but not the tool of decoration of the records for the further analysis.

Good Luck!

The small series of the articles about Scramblers by MSM Group. Direct Inversion.

Direct inversion.
Final Part III.
Direct inversion of speech spectrum.

Author: SergUA6 6.0
Band Width 2700 - 3400 Hz, it can vary, depends of tasks.
Low Range 100 - 300 Hz, it also can vary.
RX mode All types of modulation.

Sonograms

pic.1 Spectrum of inverted speech

pic.2 Spectrum of normal speech

1. The example of inverted speech, point(frequency) of inversion is 3600 Hz.

2. Exactly restored inverted speech.

Direct (simple) inversion - is the direct(simple) inversion of spectrum. It is one of the most widespread sorts of speech's masking. It is easily recognised by ear (in the case of absence of the strong interferences) and by the form the spectrum: it is well-visible on the spectrum, that the main energy is concentrated in the upper band of the frequencys, what is unusual for speech. Those who saw a normal spectrum of speech and inverted atleast once , will unmistakably define inversion further, even if it is got mixed up with other features. For today this sort of masking Makes impression unless on absolutely trustful people. Direct inversion is easily defined, easily removed, and in general it is more suitable for creation of insignificant minor problems , than for masking.

Nevertheless, the direct inversion is still widely spread today, by virtue:

• of it's simplicity
• of the absense of synchronization (the weak place of all synchronized scramblers)
• of the posibility to work in conditions of the strong interferrences

And anyway the function of the fast hiding of information is realized, althought the direct inversion isn't a barrier even in real-time.

The inverted spectrum is very easily formed by following steps:

• the frequency of inversion usually around 3000-4000 is selected
• after multiplication of an initial signal (speech) with this frequency is occuring
• then the lower lateral is selected from resulted DSB signal. This lateral is the inverted spectrum of the initial signal

The modern tools allows to do it very qualitatively. The same manipulations with the signal are used for restoring.