When I mentioned not being able to see distinct pulses I was describing after recording in gqrx and then opening the file in inspectrum
My mission is to make an rtl-sdr based 1090 MHz 2 MHz oscilloscope type view showing transponder pulses Like OOK on steroids A Sent from my iPhone > On 6 Aug 2017, at 10:14 am, Kevin Reid <kpr...@switchb.org> wrote: > >> On Sat, Aug 5, 2017 at 4:45 PM, Andrew Rich <vk4...@tech-software.net> wrote: >> Question. I have a flightaware blue rtl dongle for adsb. It picks up >> aircraft some 100 kms away ok. But when I run it with a software defined >> radio I don't see great amplitudes . Why is that ? I would have expected to >> see quite large signal peaks on the sdr program . Is it because the signal >> is spread out over 2 MHz that I can see a distinct signal strength ? Does >> the signal need to be compressed down to a narrower bandwidth ? > > These signals are extremely short in duration. Most SDR software does not > display all of the input signal in the waterfall, but samples it according to > the chosen display frame rate / scrolling speed, so any signal between those > samples will be missed. You need a rate much greater than 60 Hz to > consistently see these signals. (This does not mean you need a super-fast > monitor, just that the waterfall will scroll more than one row/pixel per > display frame.) > > If you have gr-osmosdr and gr-fosphor installed, try: > > osmocom_fft -F > > and enter 1090M for frequency and 2.4M for sample rate. You should see plenty > of horizontal lines flying by, as gr-fosphor is designed to use and display > 100% of the input signal. > > My own ShinySDR can also do high enough FFT rates and includes ADS-B decoding.
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