Re: [Hackrf-dev] 1090 MHz

[Andrew Rich]

I am wondering if I can read the I and Q file with a script language such as 
perl and make a display 

I have used perl and gd graph for this before

A 

Sent from my iPhone

> On 6 Aug 2017, at 10:14 am, Kevin Reid  wrote:
> 
> gr-fosphor

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Re: [Hackrf-dev] 1090 MHz

[Andrew Rich]

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  wrote:
> 
>> On Sat, Aug 5, 2017 at 4:45 PM, Andrew Rich  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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Re: [Hackrf-dev] 1090 MHz

[Kevin Reid]

On Sat, Aug 5, 2017 at 4:45 PM, Andrew Rich 
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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