Thank you Kevin

The data rate of sampling is 2MHz

I have a full install of gnu radio here perhaps I can play with some scope 
sinks ? 

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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