[time-nuts] Unified VCXO Carrier Board

Gerhard Hoffmann dk4xp at arcor.de
Sun Oct 25 18:56:13 EDT 2015

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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