Version 6.1.0.3: SA OFDM Module expansion.

SA update to version 6.1.0.3

In version 6.1.0.3 we continue to expand possibilities of SA OFDM module.

New components are added in the module(new components are selected with red color), old ones are moved to more convenient positions. The general view of the module:

Description of the new elements:

1 - regulation of FFT image scale by vertical

2 - moving of FFT image

3 - shift/displacement of the whole signal, for the fast correction of inaccurate position of the signal on frequency. Accuracy is in 1 hrz.

4 - regulation of FFT image scale by horizontal. The regulation is discrete.

Other elements are same as in previous version.

Detailed description:

The working window is divided into two parts.

Top part: is intended for output of the image of a correlative triangle and the various additional information. It is also used for exact positioning of the signal's LS concerning to the marker (the yellow line in the middle).

Bottom part: for output of image of FFT spectrum.

Let's consider the common example of operation with the new elements of OFDM module.

Let’s take an already known signal DRM from our site. As we already know, clock frequency of manipulation is about 37 Hertz, thus it is possible to reduce strongly time of calculations, by having installed lower limit of speed at search of LS and LG at 36-37 a Hertz, and upper limit at 38-39.

"The magic triangle" has two sides, left is the "good one", right is the "bad one" (an explanation of this feature will be described in the OFDM module tutorial part II).

Here we consider the common approaches.

For this purpose that Operation FFT would be spent really over "correct" LU, it is necessary to locate the signal so, that the marker would be situated or on "the good" side or exactly on the peak.

Actually, it is better to locate the signal on the middle of the good side.

For exact positioning of the signal concerning to marker, it is simply necessary to click on point of a slope of the triangle, and the signal automatically will be taken up into needed position. For position specification, it is possible to do smaller steps in hand-held, through the left and right buttons of the slider of moving on a signal.

After the signal will be exposed in the necessary:

to regulate view of FFT image,

to correct signal's shift by maximum of the triangle's peak

and, in general, to estimate that purely it has turned out.

The main purpose of all these operations is to receive FFT picture of representation LU of a part of the symbol, this part is pure information itself. Moving on the signal symbol-by-symbol, we can learn a lot of interesting and useful information. For example:

how many frequencies are used in the concrete symbol,

how many of them are used in general

and others undetectable before/earlier things.

For example, on this signal to learn: how many channels are used, we need to count them in hand-held, or to use special markers to count them. If precisely to take place on the most left frequency of FFT image, and to make double cliques, this frequency will be marked by two (cliques double) markers; now, if to click precisely on the most right frequency, one of markers "will go" into it.

In the window of correlative triangle it is possible to read, how many frequencies are between the markers, what are the frequencies for the lower channel and for the upper one, what common spectrum is occupied with working channels and etc.

Concerning to this signal as result we have :

1)in total, there are 229 working channels

2)there are three, from them, which are located exactly on centre are not used( it is visible on all symbols) from the remained 226 channels, there are three more are pilots-tones.

Thus 223 channels participate in information transmission. The signal’s spectrum occupies the bar in 9500 Hrz. In reality, it is a bit wider, as the channel is not a line, the line is in frequency area after FFT and this line is only for one symbol, instead of whole signal in time.

Taking into account, all information from the previous update SA to version 6.1.0.0/1 and article SA - operation with OFDM module, these new tools are certainly essentially expand possibilities of analysis OFDM in SA. Detailed tutorial about how to use new possibilities of SA OFDM module, and further development and improvement of SA OFDM Module will appear soon.

Good luck~

MPSK: QMAC signal.

QMAC

MPSK, 30-th Ch, Br~43.1, Sh~53-54, + 1 Ch as synchro

Author: SergUA6

Band Width 2000 Hz

Low Range ~400 Hz, shift is possible.

Baud Rate ~43.1 Hz

n-Ary (PSK/MPSK) PSK-8(pi/4 DQPSK)

Count of Carriers 20+10+1

Step between carriers ~53-54 Hz

RX mode SSB

Here is the record of this signal.

Sonograms:

pic.1 General view

pic.2 Speed in the channel

pic.3 Detalization

Diagrams:

pic.4 Phase constellation in the channel

QMAC - it is well known enough bar of HF equipment. There is an example of it's work in the record. The signal is multichannel, with obvious separating of channels. It is not classical OFDM signal, although, at first view it looks similar to OFDM. The signal has bright enough features. The record is made in mp3 format initially, so the quality of the record is so-so, it could be better.

Signals Analyzer: 2 license keys for the price of 1.

I guess this information will be usefull : everyone is able to get SA two license keys for the price of one.

Since Jule(2009), after purchasing the first SA license key, we send the second SA license key free of charge. Since the most part of users, as a rule, have two working computers.

I'v decided publish this information in my blog, because still most of people do not know about this ability to get 2 keys for the price of 1.

It is official information from our official site.

Sincerely yours, Maria and MSM Group.

Signals Analyzer: SA - OFDM module detailed tutorial. Part I.

SA - OFDM module detailed tutorial. Part I.

This tutorial is intented to help with solving difficult enough tasks of OFDM analysis.

The purpose of this tutorial - is to show what is possible to learn/understand/define with the help of current implementation of SA OFDM module and small "magic triangle":).

Click here to read full OFDM module SA tutorial by MSM Group.

From this SA OFDM module tutroial you will know:

• how to define the magic OFDM triangle
• how to recognize the right one triangle, in case, when there are several triangles in the signal
• when triangle can be negative and what does it mean
• what the correct "magic triangle" should look like
• specifics of "behavour" of the correct "magic OFDM triangle"
• and more interesting and usefull features for effective analysis of OFDM signals with help of SA OFDM module.

Soon the second part of OFDM module tutorial will appear.

Yours sincerely, Maria and MSM Group.

The unqiue OFDM module is added: Signals Analyzer updated. version 6.1.0.0/1.

Signals Analyzer new updated version 6.1.0.0/1.

In SA version 6.1.0.0/1 OFDM module is added. New SA OFDM module is the unqiue tool, which do not have analogues.

The detailed description of OFDM module is available in our site. Click here to read detailed OFDM module tutorial.

This tutorial is "must read", it is short, but infromative description of princples of OFDM analysis and principles of work with SA OFDM module.

Everyday more OFDM signals are appearing, and they are always problematical for the analysis. SA OFDM Module is intented to help and greatly simplify the analysis of OFDM signals.

From our description of version 6.1.0.0/0 You will know:

• basics and princples of OFDM analysis
• structure of OFDM signals
• "Magic traingle" as the sign of OFDM presence
• how to recognize "Magic triangle"
• easy steps of how to use OFDM module
• the results of SA OFDM module work.

Current implementation of SA OFDM module is only the first step in this direction. Further we will expand and develop OFDM module to receiving of constellation of the separate channel, to compensation of inaccuracies of sampling rate and displacement by frequency, and if it ill be possible, to OFDM module full automation of putting to rights parameters of record.

We are also planning to write very detailed and usefull article about work in SA OFDM Module, because possibilities of SA OFDM module are great, and some part of very vexed questions(which are often discussed on forums), can be easily enough solved with SA OFDM module help.

Sincerely, Maria and MSM Group.

What is signals analysis? And why the signals must be analyzed?

What is signals analysis? What is it nessecary for? Why is it not possible to use decoders without analysis of the signals?

Author: SergUa6 and other MSM Group members.

We receive many letters with such questions, despite the fact, that the answers to these questions are stated in number of our articles, we have decided to make this short, but informative article. Okay, let's begin from start.

Everyone who has receiver heard not clear sounds and strange signals, and each time there is the question what is it? Only extremely small amount of people can exactly identify these signals and sounds for sure. While most number of people still suppose, that the only one way to identify the signals it is their ears. This is an absolute error.

Let's consider "analysis by ear" on the real examples and situations.

Examples of What is impossible to do by "ear-analysis":

• to distinguish OFDM with 20th channels from OFDM with 18 channels
• to hear the difference between OFDM with manipulation speed 50 and 45
• to differ PSK from QAM
• to distinguish PSK-8 from PSK-4
• to hear the difference between GFSK from MSK
• to distinguish FSK with speed 1200 from PSK with speed 1200
• to distinguish MFSK-32 from MSFSK-30
• ear can't exactly define that frequency spacing is 110 for example, instead of 100
• You can't distinguish MFSK-64 from MFSK-60 by ear

I can endlessly countine this list of the real and widespread situations ,where "ear-analysis " fails and simply doesn't work.

Ofcourse it is possible to distinguish CW from RTTY by ear, same as we can differ male and female voice and etc. But it is better to close the question about abilities of ear-analysis. With each day there are more and more digital signals and protocols are appearing, already for today there are more then thoudands types of them, and all that can't be identified and analyzed by "ear-analysis". Let's leave for ears things which are ment for them: music, speech, CW.

We were surprised by the fact that there are people, who believe in "ear-analysis", mostly that part of people believes that there are only two types of the signals: CW and RTTY. Thus, "ear-analysist" name everything what is not getting under these two cathegories as "digit" type.

The main function of the signals analysis - is exact and precise definition of parametres of a signal, such as: speed, sort of manipulation and much more. That allows to identify the signal absolutely precisely and authentically.

pic.1 Function of Signals Analysis

The picture 1 shows the purposes and the place of analysis. To us it is well-known that many people ignore the analysis basically, because they believe that decoders "will understand" and decode any signal and even unknown sound. Probably many people from those who are reading this article, got into situation when the decoder program produces random set of digits or characters. And there are no ways to understand what are the reasons for it, and how much authentic is this set of characters and digits or is it simply random trash?

I don't think that i'm opening the big secret: but all decoders work only with that type of signals, for which these decoders were specially created. In case if the signal has another parameters, like different speed, or another modulation, or any other parameteres from the expected ones, then even best decoder can't realize it's functions and don't decode anything.

Ofcourse the good decoder program has customised parametres, but how it is possible to expose/specify the parametres, if they are not defined precisely or not even known at all? And where is a guarantee, what you try to decode some correctly identified signal, instead of absolutely another?

The good analyzer will help with solution of all these problems:

• with precise definition of parametres of the signal
• with identification of the signal
• with a choice of the suitable decoder, for any signal which you have accepted/have written.

pic.2

As it is well-visible from picture 2: it is impossible to decode any sound and signal without Signals Analysis.

The analysis itself is not so hard as it may seem at first look, but it requires training and learning as any other professional or hobby sphere. It is same situation when : as soon as you learn how to read books at school - you open another interesting world, while illiterate person do not even know about existence of such world.

But if to meet the illiterate person today is uncommon thing, to meet "ear-analyst" is the very usual situation, althought "ear-analysis" is very similar to illiteracy:)

MSM Group is applying all best efforts and doing all possible and also impossible, to help everyone who wants to become engaged into signals analysis and develop their skills in that direction.

Good luck!

FSK: Russian native Airforce "Chayka" - telecode "Chayka"

Russian Airforce "Chayka" - telecode "Chayka"

Command/short message system, crypto, FSK-2.

• An example of the signal with frequency manipulation in 75Hz (this record was send us by PassTR)
• An example of the signal with frequency manipulation in 150Hz (this record was send us by Skif585)

Author: SergUA6

Band Width ~ 600 Hz

Low Range ~ 500 Hz, shift is possible, recieveing in SSB

Baud Rate 75, 150, 300, 1200 Hz

Count of Carriers 2 well visible frequency of manipulation on speed in 75Hz, but on 150-300Hz it will be problematic

Step between carriers 500 Hz

RX mode SSB

Sonograms:

pic.1 General view

pic.2 Speed of manipulation

pic.3 The repeated fragment

Diagrams:

pic.1 The exact frequency spacing

Russian Airforce "Chayka" - One of native Russian systems (equipment "Chayka") of interactions of military air forces and land stations.

It is old enough system, is probably still used today, because the transmission is encrypted and it is hard enought to identify it with high level of reliability.

An implicit signs of this system: the preamble presence, an alternation of tones with frequency of manipulation in the beginning, and also rare enough rating of frequencies 500 Hz. There is well visible presence of the repeating part, which is aldo vegin from the short preamble, on the third sonogram . Speed is 1200, it is most likely used on VHF a range (usual practice), other speeds are used for connection on HF. Sea-gull is the English translation for Russian word "Chayka:'.