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

[intermilan]

   Thanks again.
   I have found the code.But what I want to know is why  the value of the LO offset is automatic set at 4M. Why not other values?Is there any reasons for it? 
 
                                                                                                   Thank you.
 
> Date: Thu, 5 Aug 2010 19:12:12 -0700
> From: address@hidden
> To: address@hidden
> Subject: Re: [Discuss-gnuradio] doubt about the tune()
>
> On Thu, Aug 05, 2010 at 09:10:50AM +0800, intermilan wrote:
> >
> > 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?
>
> The value you're talking about is called "lo_offset" in the code, and
> is an attribute of the daughterboard class. Some have a zero for their
> offset. The default value for each was choosen as a reasonable compromise.
>
> In python, if db is a daughterboard object,
>
> off = db.lo_offset() # Return the current LO Offset
>
> db.set_lo_offset(1.0e6) # Set LO offset to 1MHz
>
> IIRC, after calling set_lo_offset it doesn't take effect until the
> next time you call "tune"
>
> See http://gnuradio.org/doc/doxygen/classdb__base.html
>
> To possibly head off some other questions, please take a look at:
>
> http://gnuradio.org/doc/doxygen/classusrp__standard__rx.html
> http://gnuradio.org/doc/doxygen/classusrp__standard__tx.html
>
> And of course, there's always the source code :-)
>
> Eric
>
>
> >
> > > 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
> >