Re: [Discuss-gnuradio] Re: How to syncronize 2 XCVR2450 daughterbords

[Matt Ettus]

Bruhtesfa Ebrahim wrote:
> Jason Uher wrote:
> > > So, could you explain me how to syncronize these boards to use same
> > > oscillator and where can i get detailed information about the steps to
> > > make it.
> > > Also, is there some other way to decrease phase noise between
> > > daughterboards?
> > >
> > > thanks!
> > >
> > > Bruhtesfa
> > > --
> >
> > The instructions for linking the clocks are here:
> > http://www.gnuradio.org/trac/wiki/USRPClockingNotes
> >
> > Jason
>
> Thanks!
>
> But I am confused with one thing.
>
> I have read that the VCO on daugherbords uses PLL frequency synthesizer 
> by using the USRP clock as a reference. If I syncronize the two USRPs(to 
> work as a master and slave), will the Daughterboards,XCVR2450 operating 
> on them become frequency and phase synchronized?

YES.  That is the whole point.

Each XCVR2450 has its own local oscillator which is locked to the master 
clock on the USRP motherboard.  You can make both USRPs share the same 
master clock by following the directions above.  You CANNOT make both 
XCVRs use the same local oscillator, you can only make them lock their 
own LOs to the master clock.  However, both will then produce 
phase-locked, frequency-locked output.


> Also on the USRP clocking notes, a step is desribed to "disable the 
> daughterboard clock and enable the motherboard clock". So, which is the 
> reference for the PLL frequency synthesizer by default, the 
> daughterboard clock or the motherboard clock?


That does not apply to you.  That is for old RFX boards, not XCVR2450 
boards.

Matt