Re: [Discuss-gnuradio] Failure of sending square wave over USRPs (back-to-back)

[Activecat]

On Sat, Mar 15, 2014 at 11:14 AM, Marcus D. Leech <address@hidden> wrote:
> The SBX does analog downconversion, nothing more.  It knows nothing about
> the incoming signal, and doesn't demodulate it in any way.
>
> That is what SDR is all about--the signals are represented as
> complex-baseband (i/Q) format for processing by computer algorithms.
>
> The SBX (or any other daughtercard) is simply doing downconversion (or,
> upconversion for TX).

Even the simplest quadrature downconversion also needs to avoid clock
drift.  http://en.wikipedia.org/wiki/Quadrature_modulation#Clocking

If your "analog downconversion" above refers to quadrature
downconversion, then it is very important to have a phase lock loop
(PLL) on the SBX to avoid clock drift.

How could this PLL only present at the host (gnuradio flow graph), but
not Ettus SBX daughtercard ?
Does the flow-graph PLL able to correct all effects due to clock drift of SBX?