[time-nuts] trimble Thunderbolt, how to get 25 or 27 mHz from it??

John Ackermann N8UR jra at febo.com
Fri Jan 19 08:01:16 EST 2018

Sorry to hijack the thread, but the Si5351 looks interesting for another 
project I'm working on.  I know it specifies "low jitter" but has anyone 
looked at the phase noise?  Is it usable for RF applications?


On 01/18/2018 08:53 AM, D. Jeff Dionne wrote:
> Chris,
> You don't need to do that.  The SiLabs part will accept the 10MHz sin from an OCXO directly into the XA pin.  That pin normally connects to a crystal, so there is a high gain amp in the chip to square it up already... I did the tests a while back, see the thread here:
> https://www.silabs.com/community/timing/forum.topic.html/si5351_msop10_packag-wocK
> Caveats: others had trouble with biasing, and found just squaring the OCXO up first worked for them. SiLabs software is not set up to allow any other frequencies except 25 or 27MHz, so you do need to calculate the register values yourself.
> J.
>> Is there an easy way to get 25 or 27 MHz from my Trimble Thunderbolt as a reference clock at 1v P to P square wave for a Si5351a synthesizer chip please? I have the David Partridge divider board from way back that is still going strong, but 25 MHz is not an option as it divides only. Thanks, please keep replies to the level an idiot might comprehend :) -- Best Regards, Chris Wilson. mailto: chris at chriswilson.tv
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