Re: [Discuss-gnuradio] Reference Clock power level for Ettus N210

[Marcus Müller]

Hi,
looking at the N200 schematics from files.ettus.com, I'd say:
stick to the 0dBm, your clock signal has to pass a transformer and some 
safety/matching circuitry and still ought to be more accurate than the on-board 
VCTCXO; the clock multiplexer 
(http://www.micrel.com/index.php/en/products/clock-timing/clock-data-distribution/multiplexers/article/29-sy89545l.html)
 datasheet says it needs at least a voltage swing of 0.1V after that.
I'm not very much of a circuits person, but I think you won't deteriorate much 
of your clock accuracy by using a clock buffer, which are quite inexpensive (if 
you need but one and are not afraid to solder... TI gives away samples for 
free).
Then again, you're trying to achieve a better clock performance than the 
on-board 10MHz ref clock, so I guess you shouldn't start introducing cheap 
hardware in the clock signal path...

Greetings,
Marcus

PS: maybe the address@hidden mailing list is better suited for this... I've 
added that to CC:

On 04/23/2014 03:07 PM, Antonio Petrolino wrote:
> Hi,
>
> I'm using a USRP N210 and I need a 10 MHz reference clock. From ettus.com I got:
>
> "
> Ref Clock - 10 MHz
>
> Using an external 10 MHz reference clock, a square wave will offer the best 
> phase noise performance, but a sinusoid is acceptable. The reference clock 
> requires the following power level:
>
> USRP2 5 to 15 dBm
> N2XX 0 to 15 dBm
> "
>
> So in my case (N210) I should have a minimum 0 dBm signal.
> Can someone confirm this information (N2XX 0 to 15 dBm) for N210? The bad news 
> for me is I have a -15dBm 10 MHz available...
>
> Thank you,
> Antonio
>
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