Re: [Discuss-gnuradio] FSK with RFX2400

[kaleem ahmad]

I am facing another problem in (fsk_tx.py,  fsk_rx.py) , At receive end it do
not always write the received data to file. Although it always receive
signal which I can see from fft window and received 'seqno' are also printed
on command prompt but when I check the received file I find it empty.

What can be the problem....???????

Kaleem Ahmad

Firas A. wrote:
> 
> Hi,
> 
> 
> 1) See :
> http://gnuradio.org/trac/wiki/UsrpFAQ
> http://gnuradio.org/trac/wiki/UsrpFAQ/Clocking
> http://gnuradio.org/trac/wiki/UsrpFAQ/Gen
> 
> 2) To make  nearly 0 Hz frequency shift between your TX and RX you have to
> use a third device Spectrum analyzer or third USRP (no need to warry about
> its calibration since the error will be the same for both) as follows:
> 
> a) Start transmitting single tone from TX USRP (using usrp_siggen.py)
> 
> b) Observe and record spectrum analyzer received tone frequency. 
> 
> c) Stop TX USRP.
> 
> d) Start transmitting single tone from your RX USRP  (using
> usrp_siggen.py).
> 
> e) Observe spectrum analyzer received tone frequency. Adjust your
> transmitting frequency from your RX USRP until you get exactly the same
> value found in step-b
> 
> 
> 3) I appolagize about my previous post so many spelling errors!.
> 
> 
> Regards to all,
> 
> Firas
> 
> 
> --- On Thu, 7/24/08, kaleem ahmad <address@hidden> wrote:
> From: kaleem ahmad <address@hidden>
> Subject: Re: [Discuss-gnuradio] FSK with RFX2400
> To: address@hidden
> Date: Thursday, July 24, 2008, 5:07 PM
> 
> Hi, 
> 
> Can some one explain in a little bit detail about where is the clock or
> oscillator (on daughter board or on mother board) and how much is its
> resulution for RFX2400 daughter board. 
> 
> I tried to solve the problem of frequency mismatching by calculating the
> frequency shift at receiver end by using usrp_fft.py and then by
> adding/subtracting that frequency from RX USRP frequency as explained by
> Firas and Patrick. But it dont solve the problem although it improves the
> quality of data but because of this effort at least I understand that the
> problem is really some where because of frequency mismatching. 
> 
> So it will be helpful for me if some one either give some good document of
> USRP explaining clock/oscillator or just explaing the fuctionality of it
> by
> him/her self.
> 
> Thanks 
> 
> 
> 
> Firas A. wrote:
>> 
>> Hi Kaleem,
>> 
>> Each USRP has its on reference crystal oscillator. This oscillator may
>> have maximum +/- 50 PPM ( Matt said the new USRPs has maximum 20 PPM)
>> frequency error. Lets assume the error is 10 PPM in each USRP. This
>> means,
>> that at 2500 MHz (2.5 GHz) the error = 2500 * 10 = 25000 Hz = 25KHz. 
>> 
>> Now imagine that the first USRP has +25 KHz frequency deviation error and
>> the second one has - 25KHz frequency error. This means + 50 KHz frequency
>> mismtch between your TX and Rx Frequencies. This is probably what is
>> causing this high error rate that you see.
>> 
>> To solve this problem you simply do :
>> 
>> 1) Use usrp_siggen.py to send single tone at F1 frequency (For example,
>> use F1 = 2475 MHz) from your TX USRP. The best thing is F1 be the
>> frequency used in your FSK experiments.
>> 
>> 2) With your RX USRP, start usrp_fft.py with frequency F1 and decimation=
>> 128 (or 256). You should see your transmitted tone but may be it's
>> frequency is shifted. Calculate this frequency shift.
>> 
>> 3) Add/subtract this frequency shift to your RX USRP frequency tunning
>> function.
>> 
>> 4) Now your two USRPs frequency mismatch should not be the problem. If
>> the
>> errors is still there, then you have to search for another reason.
>> 
>> Regards,
>> 
>> Firas
>> 
>> 
>> 
>> --- On Wed, 7/23/08, kaleem ahmad <address@hidden> wrote:
>> From: kaleem ahmad <address@hidden>
>> Subject: Re: [Discuss-gnuradio] FSK with RFX2400
>> To: address@hidden
>> Date: Wednesday, July 23, 2008, 5:23 PM
>> 
>> I have just provided the information which can be helpful for you, and
>> the
>> code is also attached with it and a sample received file is also there
>> along
>> with actual sent file.
>> 
>> Please just scroll up and you will find my message with all this
>> information. Additionally OS is 'openSUSI' a favour of Linux. But
> if
>> you
>> still need some more info then please let me know.
>> 
>> Thaks
>> 
>> 
>> 
>> Patrick Strasser wrote:
>>> 
>>> kaleem ahmad wrote am 2008-07-23 11:38:
>>>> Dear All,
>>>> 
>>>> Can anyone also address the first part of my question aslo, I mean
> how
>> to
>>>> improve the quality of received data. I mean is it normal with GNU
>>>> Radio/USRP that we receive so currupt data or I am doing something
>> wrong.
>>>> Any suggestion please 
>>> 
>>> Before you wrote
>>> 
>>>> after using tune
>>>> to set the proper ferquency I was able to run transmitter and
> receiver
>>>  > sussfully. I didnt change anything else in the example.
>>>  > The problem is data
>>>> which I receive is too much corrupt (lot of data errors)..
>>> 
>>> Your description is not very exact. You could help us to help you with
> 
>>> more information:
>>> 
>>> What is your setup? OS, distribution, used version of packages, GNU 
>>> Radio, hardware setup, used parts (cable, antennas), environment.
>>> What do you do? Which code do you use?
>>> What did you change?
>>> What did you get? Error messages? (add _exact_ transcripts of errors)
>>> What did you expect?
>>> Please provide exact information, code should be attached. If you 
>>> changed something, mark the changes so helpers will find it easier.
>>> 
>>> If you have recorded samples of a good and bad transmissions, send us
> a 
>>> representative part of it. If you need to show more than a hand full
> of 
>>> kilobytes, put them on a web server or ftp server and provide a link.
>>> 
>>> Are you sure to have read the FAQ and introducing documentation?
>>> 
>>> Patrick
>>> -- 
>>> Engineers motto: cheap, good, fast: choose any two
>>> Patrick Strasser <patrick dot strasser at student dot tugraz dot
> at>
>>> Student of Telematik, Techn. University Graz, Austria
>>> 
>>> 
>>> 
>>> _______________________________________________
>>> Discuss-gnuradio mailing list
>>> address@hidden
>>> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>> 
>>> 
>> 
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