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Re: [Discuss-gnuradio] Mode S and ADS-B

From: Martin Dvh
Subject: Re: [Discuss-gnuradio] Mode S and ADS-B
Date: Fri, 06 Jul 2007 01:44:14 +0200
User-agent: Icedove (X11/20070607)

Eric A. Cottrell wrote:
> Hello,
> I finally checked in the infamous Mode Select code to
> branches/developers/wb1hbu/wip and I am glad this portion is done.
> I spent a couple of days cleaning the code up a little.  I also added
> some features.  Likely I missed using a few neat gnuradio functions.
> There is a usrp_oscope_ms.py program that displays the Mode Select
> signal, Reference Level, and Attributes.  Triggering off of channel 2
> (Reference Level) allows the display of Mode Select waveforms.  I made
> the attributes go negative so they are more visible.  I was surprised at
> the results.
> The usrp_mode_s_logfile.py program outputs Mode Select frame information
> to a log file.  It does no decoding of the data.  It logs the data bits
> and other attributes of the signal and error correction.  It is a good
> program to run if you are in a heavy air traffic area and want to
> generate megabytes of text within an hour.
Hi Eric,
I tried out your code.
Does it run on your machine in realtime?
I have a dual-core athlon X2 3800 and both processor go to 100 % when I run it.
(I didn't know gnuradio could use both processors , I though we still had the 

This gives me a lot of USRP overruns (UoUoUo) so it doesn't work very well this 
Does mode-s really need a samplerate of 8000000

Another question.
I know 1090 Mhz is the frequency they use in the US.
I googled for info on frequencies for mode-s and ads-b and it seems multiple 
frequencies could be used.
Does anyone know of an overview of the actual frequencies in use, at which 
(I live in the netherlands)

I tried increasing the decimation but then the code refuses to run (requires 
8000000 sps)

> 73 Eric
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