Matt Ettus wrote:
> The rev 4 and newer USRPs have a clock generator chip that is
spec'ed to
take a signal as low as 150 mV p-p. However in my testing I found I
needed a voltage as high as 8 or 9dBm. 8dBm is about .8V, so that
should still work.
Sorry if this isn't relevant to everybody on the list, but it is
*very* important to those of us who are using external clocks with the
Rev 4 USRPs.
I tried out varying clock inputs, and verified Matt's claim that 800
mV pp was required for consistent USRP operation. This didn't seem
correct to me, because Analog (who makes the clock distribution chip)
normally is very good about their specifications.
After further testing (and datasheet reading) we discovered two things:
(1) If you're using an external clock, in addition to the changes
specified under "Rev 4 USRPs - For the Slave Boards" at:
http://www.comsec.com/wiki?USRPClockingNotes
You should probably also remove C924, the 0.01 uF cap going to X2 pin 3.