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some fixes

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Carles Fernandez 2014-04-22 20:37:40 +02:00
parent 5f9e46cc23
commit 4046bcfdd4
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README.md
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** Welcome to GNSS-SDR!**
**Welcome to GNSS-SDR!**
Check [gnss-sdr.org](http://gnss-sdr.org "GNSS-SDR's Homepage") for more information about this open source GNSS software defined receiver.
@ -376,11 +376,11 @@ Getting started
1. After building the code, you will find the ```gnss-sdr``` executable file at gnss-sdr/install.
2. In post-processing mode, you have to provide a captured GNSS signal file.
1. The signal file can be easily recorded using the GNU Radio file sink in ```gr_complex<float>``` mode.
2. You will need a GPS active antenna, a [USRP](https://www.ettus.com/product) and a suitable USRP daughter board to receive GPS L1 C/A signals. GNSS-SDR require to have at least 2 MHz of bandwidth in 1.57542 GHz. (remember to enable the DC bias with the daughter board jumper).
We use the [DBSRX](https://www.ettus.com/product/details/DBSRX2) to do the task, but you can try the newer ETTUS daughter boards as well.
2. You will need a GPS active antenna, a [USRP](http://www.ettus.com/product) and a suitable USRP daughter board to receive GPS L1 C/A signals. GNSS-SDR require to have at least 2 MHz of bandwidth in 1.57542 GHz. (remember to enable the DC bias with the daughter board jumper).
We use a [DBSRX2](https://www.ettus.com/product/details/DBSRX2) to do the task, but you can try the newer Ettus' daughter boards as well.
3. The easiest way to capture a signal file is to use the GNU Radio Companion GUI. Only two blocks are needed: an USRP signal source connected to complex float file sink. You need to tune the USRP central frequency and decimation factor using USRP signal source properties box. We suggest using a decimation factor of 20 if you use the USRP2. This will give you 100/20 = 5 MSPS which will be enough to receive GPS L1 C/A signals. The front-end gain should also be configured. In our test with the DBSRX2 we obtained good results with ```G=50```.
4. Capture at least 80 seconds of signal in open sky conditions. During the process, be aware of USRP driver buffer underuns messages. If your hard disk is not fast enough to write data at this speed you can capture to a virtual RAM drive. 80 seconds of signal at 5 MSPS occupies less than 3 Gbytes using ```gr_complex<float>```.
5. If you have no access to a RF front-end, ou can download a sample raw data file (that contains GPS and Galileo signals) from [here](http://sourceforge.net/projects/gnss-sdr/files/data/).
5. If you have no access to a RF front-end, you can download a sample raw data file (that contains GPS and Galileo signals) from [here](http://sourceforge.net/projects/gnss-sdr/files/data/).
3. You are ready to configure the receiver to use your captured file among other parameters:
1. The default configuration file resides at [./conf/gnss-sdr.conf](./conf/gnss-sdr.conf).
2. You need to modify at least the following settings: