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On 03/31/2013 07:22 PM, souf308 wrote:
OK I think I actually found out how to use the info file. But I still need some help to configure the parameters in the OP25.grc and use the samples (sorry to bother you with those beginners questions) ---------------------------- Here is the info file (from the website) (dp0 S'capture-rate' p1 I250000 sS'source-decim' p2 I256 sS'source-dev' p3 S'USRP' p4 sS'center-freq' p5 F434075000.0 s. --------------- So * 'capture-rate' corresponds to the parameter 'samp_rate' in grc file hence samp_rate=250000
- 'center frequency'=434075000.0
*but what about 'channel_rate'? (=250000?)
*In this formula (channel_rate/(2.0 * math.pi * op25.SYMBOL_DEVIATION)) what is op25.SYMBOL_DEVIATION???
*what is samp_per_sym??
Thanks in advance for you help
Souf
Hi Souf, yes the capture rate is the sample rate. sample per symbol is what changes the channel rate, don't change the channel rate directly; I believe the channel rate should be between 19.2k and 43.2k. decimation changes the pre_channel rate, looks like he had it set at 256. I have found that it is best to play a file is with the flow graph set exactly as it was set when the file is captured. If you want to have a go with a capture I made I put the file up for download at: http://www.fileswap.com/dl/9kfgeOXMz/ I think the frequency, sample rate, decimation, and symbol_per_sample information is in the tar file. put a throttle right after the file source or the file will play in about 11 seconds instead of the real speed of about 40 seconds. so when you play the file first you tune to the frequency, next on the BB-1 tab you wait for the carrier freq to pop up, then go to the X-late1 tab and use the offset to get the channel at zero and narrow the bandwidth with the xlateBW slider, then go to the Dbits tab select autorange and change the marker to dots. you'll see the dots go from scattered into 4 perfect lines and you'll hear the transmission. Thanks