IQmonitor Pro - setting parameters

IQmonitor Pro often scares off potential users with an abundance of interface elements that allow you to set dozens of parameters for optimal program operation.

What does optimal mean? - these are parameters that, depending on the task at hand, will provide either the maximum accuracy of determining the parameters of transponders at an acceptable speed of their search, or the maximum speed of constructing spectra of satellite signals with the condition of finding all above-threshold transponders, or determining the parameters of subthreshold signals, or searching for ultra-low-speed ( up to beacons) transponders to ordinary PCI (ex) cards, significantly exceeding the manufacturer's declared characteristics of DVB S2 signal tuners and demodulators. So, for example, the frequency step of the spectra from 1000 kHz has been brought to 4kHz (reduced by a factor of 250), and the resolution in the HR (high-resolution) mode has increased tenfold.

In this article (and there are several planned) we will consider the selection and installation of two parameters: the Noise level and the minimum value of the RF signal power.

An example of determining the Noise Level and Min level RF

First, we set the frequency range in which we will work (Fstart - Fstop) and the frequency step per one pixel of the dF graph: 11200 - 11450 MHz and 499 kHz. By clicking the Apply button, we get the layout of the spectra plate in the upper left corner of the screen. Select the 1 MHz spectrum frequency step in the Frequency step, MHz field and press the Spectrum button - after a few tens of seconds, the RF spectrum will appear on the screen (blue curve).

Using the slider on the right side of the tablet, move the dashed purple line of the power level of the analyzed spectrum frequencies (RF threshold) so that it is below most of the minimums of the RF spectrum (-50.5 dB). After that, use the Blind Scan button to launch a "blind" scan of the spectrum.

The blue outlines of the detected transponders start to appear on the screen. Their height is equal to the SNR of the found transponders, the "legs" are placed on the bandwidth occupied by the transponder, and in the middle between them (at the carrier frequency) there is a noise level point. The vertices of the transponders are tied to the RF spectrum, and through the points of the noise level, I drew a gray line, which is close to the noise level in the studied frequency band.

Then the green line of the average noise level was drawn so that it was, if possible, below all the minimums of the RF spectrum, and the areas of the figures, which are limited by the gray noise line, above and below the green line were approximately the same. The height of this line is the Noise Level, which we enter in the corresponding field of the main program window.

The amplitude of the spectrum above this line can be adjusted with the Scale RF parameter to emphasize the wanted signals, and the dynamic range of the output below the Min level RF is non-linearly compressed for visual noise suppression, which improves the readability of the spectrum. In addition, the Min level RF is used in spectrum deconvolution to deepen the minima between adjacent transponders.

Min level RF is recommended to be selected equal to or less than the Noise level of the receiving installation relative to the Noise Level :96: