Re: [Discuss-gnuradio] doubt about the tune()

[intermilan]

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From: address@hidden
To: address@hidden
Subject: RE: [Discuss-gnuradio] doubt about the tune()
Date: Thu, 5 Aug 2010 09:10:50 +0800

       Thank you for the answer.then I have another quertion.why the value is 4M? why not other values like 3M or 5M?and can you tell me where is the code to set the DC offect?

                                                                                                                                                                     Thank you

> Date: Wed, 4 Aug 2010 10:14:32 -0700
> From: address@hidden
> To: address@hidden
> CC: address@hidden
> Subject: Re: [Discuss-gnuradio] doubt about the tune()
>
> On Wed, Aug 04, 2010 at 05:08:44PM +0800, intermilan wrote:
> >
> > hi all:
> > I recently run the test_usrp_standard_tx/rx.cc to do some test.and after I run the test_usrp_standard_tx.cc, I got the follow information:
> > which: 0
> > interp: 64
> > rf_freq: 2.5e+09
> > amp: 30000.000000
> > nsamples: 3.2e+07
> > Subdevice name is Flex 2400 Tx
> > Subdevice freq range: (2.3e+09, 2.7e+09)
> > mux: 0x000098
> > baseband rate: 2e+06
> > target_freq: 2500000000.000000
> > ok: true
> > r.baseband_freq: 2504000000.000000
> > r.dxc_freq: -4000000.000000
> > r.residual_freq: 0.000000
> > r.inverted: 0
> > xfered 3.2e+07 bytes in 4 seconds. 8.002e+06 bytes/sec. cpu time = 0
> >
> > as you can see, I want to set the frequency at 2.5G(RFX2400) ,but there is a parameter called r.basebande=2.504G.I know it is the return valus of the tune().but I want to know what is the function of this parameter and how did 2.504G come out. can anyone help me to figure it out?
> > Besides,why the frequenct of the DUC is set at -4M? how did it come out?
>
> It moves the DC offset 4MHz away from the center of your desired
> spectrum. r.baseband_freq + r.dxc_freq = target_freq.
>
> Eric