Hello everyone,
I have a few doubts related to osmocom_spectrum_sense. I want to scan the band from 925MHz to 960MHz using a HackRF with the following parameters:
- sample_rate = 10 MHz
- FFT_size = 1024
- channel_BW = 200 kHz
According to the code, the frequency_step would be then of 7.6 MHz because of an FFT overlapping of 25%.
Then the scan of the whole band, which has 35MHz, should be done in 5 different steps (the center_freq should change 5 times). The program sets the first center_freq to 928.8MHz (=925M+(7.6M/2)) and the center_freq of the last step to 966.8MHz because it computes it in the following way:
max_center_freq = min_center_freq + nsteps*freq_step = 928.8M + 5*7.6M = 966.8MHz
But I think there is a mistake there, it should be:
max_center_freq = min_center_freq + (nsteps-1)*freq_step = 928.8M + 4*7.6M = 959.2MHz
Because in my opinion the center frequencies of the five steps are 928.8MHz, 936.4MHz, 944.0MHz, 951.6MHz and 959.2MHz (there is no need of an extra step centered at 966.8MHz because being centered at 959.2MHz we are analyzing a band beyond the 960MHz limit). Is it so?
Anyway, my main problem becomes visible when I execute the script from the command line. It prints the center_freq values at each instant of time and they are not the ones that I said in the last paragraph. As you can see in the attached file it only uses the center frequencies 928.8MHz and 936.4MHz, and the values of freq are also strange because they only go from 949.4MHz to 960MHz... I think that the problem is with m.data, but I don't know where the values it contains come from.
Any explanation of why it happens or how to fix it? I hope that I was clear with the explanation.
Thank you very much!
Marc.
output