Update SA to version 6.2.2.0/1

Update SA to version 6.2.2.0/1

In this version added the ability to copy the various fragments of the signal from WF module.

Copy fragments signal from the sonograms, can not operate sufficiently exactly. This is not a problems of SA, it is a fundamental limitation FFT.

The fact that the FFT, in general case , makes a transition from time domain into the frequency domain, and such a thing as time loses its meaning. Within the FFT block does not have time, and to say exactly where in that block is one or another component of the spectrum is impossible. This leads to the fact that selecting/separating out a segment of the signal at the sonograms, there is always uncertainty within the block FFT. Sometimes this quantity is large enough. Hundreds of milliseconds or few seconds and more, depending on size of block FFT.

Copying a fragments of the signals as waveform is much more accurate, but has own problems. Impossible to say exactly, from the image of waveform, exist/included a some frequency components in the selected segment or no.

Although the selection of segments from by waveform and is much more accurate, nevertheless, also not an accurate method. Accuracy is limited to one or two samples. In general, the problem is really accurate measurements and actions, is surprisingly/unexpectedly deep and multifaceted task.

Also introduce the possibility of transferring a fragment of the signal directly in the FSK-2 dem, and solves the problem of obtaining "clean" bit stream, in many difficult cases.

A small example of obtaining a "pure" bit stream from the rather complicated to demodulate the signal.






As usual, apart from updates, fixed bugs found by users. And including minor corrections to improve the work of the various modules and the whole program.


Good Luck!

Update SA to version 6.2.1.8

Update SA to version 6.2.1.8

In this version, we fixed an error in the function of BRC (Baud Rate Correction) discovered by users, and introduce/added a two modifications.

The first.


Sometimes, it is easier to work with a relative or even abstract concepts, because no matter the specific values, but important that they fit into a certain framework. This applies to the oversampling and shifting of signal by frequency.

Usually, it is required that a signal was in the middle of the spectrum, and the sampling frequency was not much excess.

In this version You can select the frequency shift or frequency oversampling, just selecting the desired point from the list. In some cases, it greatly reduces the time and effort. Possibility of manual input for precise actions, of course, also saved.

The second

VMW module can potentially provide extremely high accuracy, at the request of Spanish colleagues, we insert in the current update stroboscopic method of measurements.

The idea is that, if the data in the record is sufficient, You can get very precise parameters of the signals.

However, there are problems, large amounts of data require very large computing and time.

Given the characteristics of the module VMW, we just calculate and to display every 1 st, 2 nd, 4 th etc lines/rows in the visualization VMW. For all the simplicity and elegance of this method, it provides exellent/perfectly accuracy of measurement.

This is one of the realizations of the stroboscopic measurement method. And like all such methods, it provides increased accuracy with increasing period gating, in this case by rows.

In the screenshot above, perfectly clear that the old method to accurately measure the period of the sine (exactly 1000 Hz) is extremely difficult, error of 20 nanoseconds is not noticeable. In really, an error and in 100 nanoseconds is very difficult to visually detect the slope of the lines is enough small.

A new method for gating each 1024 lines, clearly and accurately detect the difference in a nanosecond! Actually the accuracy is increased compared with the first/old method in 1024 times.

Need to be cautious, as stroboscopic methods for periodic signals may give a false and sometimes very misleading results, due to skip of parts of signal. To prevent this, you should always start measuring without gating. And gradually increasing the accuracy to measurement via of gating.

Good Luck!

SA Update to version v 6.2.1.6

SA Update to version v 6.2.1.6

In this version speed of calculations, at search of a correlative triangle in OFDM module, is increased non less then 30%.

The algorithm of resampling of records is completely reconsidered.

Earlier we marked, that resampling algorithm in SA though provides precision accuracy on sampling rate, nevertheless distorts Amplitude frequency characteristic/Phase frequency characteristic (AFC/PFC) of signals. Though, it does not have the great importance in overwhelming majority of cases, as distortions affect the upper part of a spectrum. But the problem exists, we knew about it, and we promised whenever possible to solve it.

The problem is most brightly shown at resampling of OFDM signals, as OFDM signals are very sensitive to this sort of distortions.

In current version 6.2.1.6, resampling function works practically with absolute accuracy, in reasonable limits of course.

It is most easier to show the difference on the sonograms.

1

An old algorithm: there are distortions AFC/PFC on the upper channels of OFDM signal, which are visible even on sonogram.

New algorithm: there are no distortions.

2

An old algorithm: resampling of the record with sampling rate 68 mHz, on 60 mHz. As anti-alias filters aren't used, manual pre-processing is demanded, for removal of unnecessary components of the spectrum.

New algorithm: an excellent quality. Anti-alias filters are used by default. Although it isn't the main criteria of qualitative resampling, nevertheless it strongly simplifies operation with resampling function , excepting manual pre-processing.

Also the minor bug, which were found out by our users are solved.

Good luck!

FSK: "Avaris" - domestic(Russia) system of special communication on VHF

"Avaris" - special-radio service(VHF), FM-GFSK, Br-9600.

Author: SergUA6

Band Width ~12000 Hz

Baud Rate 9600 Hz

RX mode Source I/Q record

The record of fragment of work of "Avaris" system.

Sonograms:

pic.1 General view

Diagrams:

pic.2 Signals demodulation

Pictures:

pic.3 General structure of the signal

"Avaris" - domestic(Russia) system of special communication. In a basis of this system, lies using of special repeaters under similar mark "Avaris". Repeaters provide expect the basic functions, also functions of recording coded/encrypted speech messages and their subsequent transfer to concrete addressees or group of users. In this system, and not only in this, speech is digitized by means of the delta modulation. The received digital stream is ciphered and transferred, in this case, GFSK modulation is used.

SA Update: RRC filter is added.

SA update to version 6.2.1.4

Three new elements are added:

1.In the module of form viewer: median filter had been replaced by new RRC filter. By default alpha = 0.5

2.RRC filter is also added in the module of FSK-2 demodulator.Alpha=0.5 by default. If RRC filter is in OFF state, then the filter, which is analogous to the main filter, works in the signal's form viewer module.

3. The following elements are added in the module of FSK-2 demodulator:

1) elements of image vertical scaling

2) an indicator of filtration process

3) the buttons of filtration start and back into initial state.

4) the cutoff range(frequency) in RRC filter can be specified from 5 Hz to Fd/2 Hz. where Hd is sampling rate. In usual(special, soft) filter cutoff range can be specified only from 30Hz to Fd/3, in the force of realization specifications.

Special attention is focused on saving of signal's fase before filtration and after filtration. The phase do not change

guaranteed.

Also some minor bugs, which had been found by users, are correct.

MFSK: NEXEDGE

NEXEDGE

NXDN - 4800, 2400. C4FM, BW ~ 10000 Hz, 5000 Hz

1. an example of NXDN with manipulation speed 4800, sendby Rulez Reloaded

2. an example of NXDN with manipulation speed 2400, send by Rulez Reloaded

Author: SergUA6

Band Width ~10000 or 5000 Hz

Baud Rate 4800 or 2400 Hz

n-Ary (PSK/MPSK) C4FM

Count of Carriers 4

ACF ~ 80, ~ 40 ms

RX mode Source IF record

Sonograms:

pic.1 General veiw NXDN with speed 4800

pic.2 Generalview NXDN with speed 2400

Diagrams:

pic.3 Manipulation speed 4800

pic.4 Manipulation speed 2400

Pictures:

pic.5 Sub-optimum demodulation 4800

pic.6 Sub-optimum demodulation 2400

pic.7 ACF NXDN in 2400 mode, only 80 ms

NEXEDGE - is the communication system using NXDN protocol. NXDN is the joint development Kenwood and ICOM companies. The protocol is declared as opened one, modulation which is used on VHF, is the classical C4FM. The Same type of modulation is also used in the other

known communication system APCO-25 on the basis of standard P-25.

On it similarity comes to an end, P-25 and NXDN are incompatible.

As a whole, the signal is easily identified, especially in SA last versions: there are special possibilities, for confident enough identification C4FM. Two variants of the signal are prepresented on the records: broadband, under the standard channel by a strip/band 12.5 kHz, and narrow-band under the channel 6.25 Khz. The maximum technical speed accordingly in a broadband mode 9600 bps, in narrow-band 4800 bps. Thus clock frequency of manipulation for C4FM turns out twice less, 4800 Hz and 2400 Hz.

SA update to version v 6.2.1.2: An output from discriminator and program processing.

SA update to version v 6.2.1.2

Two new elements are added.

The double half-wave detector, and the module of FSK-2 demodulator.

The double half-wave detector, generally, has narrow enought area of application, and as a whole, it strongly loses to the quadrature detector. However, has a high processing speed, and in some cases, it allows to solve problems of reception of clock frequency of manipulation, while other methods work very poorly or don't work absolutely.

Usually, the problems with reception of clock frequency of manipulation occur, when the record represents as not the radiosignal, but the voltage of manipulation, received after FSK, FМ or АМ detector.

Just for such cases the double-half wave detector, which solves this problem successfully had been added. In generall it concerns FSK-2, modulations C4FM and some other signals.

More important updating, is the introduction of module of FSK-2 demodulator.

Current realization is the base concept, and means further development.

Synchronization on clock frequency is carried out manually (at least currently). It isn't difficult, but demands some skills.

Exact phasing is should be done in last moment/time!

The first step: to expose/specify exact clock frequency. It should be done by zero beating, which are well visible at the corresponding scale on an axis X. Frequency is entered directly in manual from the keyboard (at it finished of input must be pressing of "Enter" key), or changes through control elements on the panel.

The second step: is the installation of rough phasing through the slider in the bottom of display window.

Last step, is adjustment of a phase for reception of as much as possible accurate clear picture.

After all these actions, a line of action/line of solution should be exposed in the necessary position (usually on the middle), if the signal is qualitative enough, and it was possible to receive a good picture of separation of levels. And it becomes possible to get the bit stream. All what is above the line of solution is considered to 1(0), all that is below the line of solution to 0(1).

I want to underline, although the module is intended for FSK-2 signals, it has much more extensive application field, as all SA tools.

In particular, with its help it is possible to realize the following tasks easily:

1 - to identify such kind of modulation as C4FM

2 - To realize a quality estimation of various signals etc.

The more detailed information about how to work with this module and practical application of new SA features is described in the article An output from discriminator and program processing.

Good Luck~