On Sat, Aug 5, 2017 at 4:45 PM, Andrew Rich <vk4...@tech-software.net>

> 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
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