[time-nuts] Unified VCXO Carrier Board

[Bruce Griffiths]

On Sunday, October 25, 2015 11:56:13 PM Gerhard Hoffmann wrote:
> Am 24.10.2015 um 22:21 schrieb Bruce Griffiths:
> > On Saturday, October 24, 2015 09:03:21 AM Charles Steinmetz wrote:
> >> The spec sheet says both TimePod inputs accept -5 to +20dBm into 
50
> >> ohms.  -5dBm is less than 0.4Vp-p, which requires less than +/-4mA
> >> from the source, so a 0-5v comparator output feeding a
> >> capacitor and a 560 ohm series resistor should work fine as long as
> >> the comparator can source and sink at least 4mA.
> > 
> > The fly in the ointment is that with such low level inputs (the LTC6957-4
> > evaluation board will deliver +4dBm into 50 ohm) the Timepod phase 
noise
> > floor is uncomfortably close to the phase noise floor of the LTC6957.
> > 
> >> Alternatively, a 0-5v comparator output could be buffered with three
> >> 'AC04 inverters in parallel, or an 'AC line driver -- but that adds s
> >> the PN of the gates.
> > 
> > Not if one uses a pair of drivers one to drive the Timepod Ch0 input 
and
> > one to drive the Timepod CH2 input.
> > 
> > It would perhaps be useful to measure the PN characteristics of 
several
> > comparators and other sine to square converter circuits using a 
Timepod
> > or equivalent.
> 
> For the sake of repeatability, could we agree on a common setup?
> Timepod would be ok for me. Levels, sources, filters, splitters...
> 
> regards, Gerhard
> 
> 
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Gerhard

I'll start another thread on this initially detailing how I measured the PN of 
the LT6957-4.

Bruce