Sorry for my indecently short answer - there was not enough time and effort, plus the power was turned off when I almost finished translating my article:
IQmonitor Pro program - operation in extended search range mode
I debugged the IQmonitor Pro program mode - work with an extended search range.
This mode is due to the use of the third harmonic of the local oscillator of the PCI card tuner
allows you to expand the range of actually received signals up to theoretically 7.5 GHz
and up to 1.9 GHz practically.
First, let's see how it works on the example of the 0.8°W position - double-click on
peak of the transponder, which is at a frequency below the lower limit of the upper Ku subband:
At 11297 MHz (253 MHz below the lower frequency of the Ku high subband) 2.5dB below the lock threshold
a signal with SR=30000 kC/sec, FEC 3/4 and 8PSK modulation was registered. Moreover, occupied by him in fact
the bandwidth is exactly three times the width of the transponder peak in the spectrum.
This is a direct indication that the signal is received at the third harmonic of the local oscillator. Therefore, we turn on the mode
advanced search by checking the Expand search band checkbox
Now in the hint near the cursor, in addition to the frequency at its position, a second line has appeared, which indicates
frequency of the transponder that can be received at the third harmonic of the local oscillator by double-clicking on the spectrum:
As you can see, this frequency is 1.4 GHz higher and lies on the upper edge of the Ku high subband.
Let's try to find this transponder there:
As you can see, we have successfully locked this transponder at the "true" frequency at the first harmonic of the local oscillator.
Moreover, with a large margin for lock - after all, the amplitude of the first harmonic of the local oscillator is significantly higher than the amplitude of its third harmonic.
If you spare your time and scroll through my blog in the opposite direction, you will find a picture,
which confirms the reception of a television image not only on the third, but on an even weaker
FIFTH! ! ! harmonics of the local oscillator.
And now look at an example of using the OMICOM budget card, which, according to the passport, cannot
accept transponders with a center frequency greater than 12750 MHz and symbol rates less
1000 kS/s, for receiving an ultra-low-speed transponder at the frequency of the new, extended Ku
range:
Don't let the headline fool you - before experimenting with the Turksat 5A, I watched the news on
Firebird and just forgot to change the name of the satellite when the USALS system turned the antenna with the aperture
1.05m at 30.9°E.
It is easy to see that on the usual RF spectrum in the Ku band, the transponder is barely distinguishable
hump with an amplitude of ~1 dBm. I would never have paid attention to him, but on the spectrum of high
resolution with a frequency step of 124 kHz, the IQmonitor Pro program singled out the peak with one spectral line
amplitude of 5.5 dB, which is perfectly confirmed by the transponder tuning time curve.
In the advanced search mode, a signal was successfully found at a frequency higher than 1.9 GHz, which occupies
band three times the frequency step of the HR spectrum, that is, a transponder from the new range with a frequency
13424 MHz was received through the third harmonic at 11541 MHz!
The IQmonitor Pro program made it possible to improve the performance of the budget card twice in terms of frequency and four times in terms of
symbol rate. In fairness, I must say that the OMICOM card was tuned by me -
screens, a fan were added, and the supply voltage ripple, which reached 21 mV, was smoothed out
three electrolytic capacitors. But the main merit still belongs to the IQmonitor Pro program.