Re: [Discuss-gnuradio] FSK modulation/demodulation for Universal Access Transceiver

[Marcus Müller]

Hi Olivier!

Nice to meet you.
So, first off, a hint: GRC has a "screen capture" menu / toolbar button that lets you just export your GRC canvas, so you don't have to make a screenshot of your whole dual-desktop screen (by the way, cropping that would have worked, too ;) ).

UAT == ADS-B transmitter, right? Have you seen [1], and are you aware of Nick Foster's gr-air-modes, an ADS-B receiver?

So, we'd love to help you, but "only gibberish" is hardly a good error description. Does the RX signal in time domain look OK, or is there very little amplitude, or values close to 1, indicating clipping? What about frequency domain, does the RX signal resemble the TX signal?

Then: UHD specifically tells you there is something wrong with how you've configured things. You will need to fix that first.

Best regards,
Marcus

[1] https://www.youtube.com/watch?v=NSLqRXyxiBo

On 26.05.2016 17:03, Olivier Goyette wrote:

Hi everyone,

I'm currently doing an internship at school and i'm working with USRP N210 and GNUradio. It's been a month since I began working with these 2 tools, so excuse me if I may sound noob, but I really need some help. I've been asked to start thinking about developing an UAT for civil aviation. I've read a ton of standards and papers concerning this new technology, so I won't relate it all over here, but the main thing about it is that it uses FSK mod/demod for the information to be transmitted and received.

I'm currently stuck on a problem that's been haunting me for the last 2 weeks and that's why i'm asking for your guidance. When I run the mod/demod on simulation(attached #1), everything works fine. I'm sending abcdefghijklmopqr and on the receiving side i got the same thing. Now the problem is that when i'm trying to send it via the USRP with a cable between RX and TX(attached #2), i only get gibberish on the receiving side !

What have I done wrong ? I don't get why it's not working.

Thank you for your time, your help will be more than welcome

Olivier

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