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

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? Thanks, John ---- 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 > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

On Jan 19, 2018 6:01 AM, "John Ackermann N8UR" <jra@febo.com> wrote: > 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? > Datasheet states jitter in the 40-70 ps range. That is not very good. If you want something suitable for RF applications, look at the Si5328. It has jitter on the order of 300fs. I believe Leo Bodnar uses it in his GPSDOs and I can confirm the phase noise and Allan Deviation others have found and it is suitable for me for RF applications. It is not nearly as good as the Thunderbolt though. It will generate almost any frequency you want. Mark >

Hi Mark -- Thanks! To clarify, when you say you've found "it" acceptable, you're referring to the 5328? What caught my eye about the 5351 was the three (or eight) outputs. My idea was to build a board that would provide independent LO oscillators for multiple VHF/UHF transverters. It looks like the 5328 has two outputs, which is still useful but would require putting two or three of them on the board. Which isn't the end of the world. Thanks, John ---- On 1/19/2018 8:56 AM, Mark Goldberg wrote: > On Jan 19, 2018 6:01 AM, "John Ackermann N8UR" <jra@febo.com> wrote: > >> 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? >> > > > Datasheet states jitter in the 40-70 ps range. That is not very good. If > you want something suitable for RF applications, look at the Si5328. It has > jitter on the order of 300fs. > > I believe Leo Bodnar uses it in his GPSDOs and I can confirm the phase > noise and Allan Deviation others have found and it is suitable for me for > RF applications. It is not nearly as good as the Thunderbolt though. It > will generate almost any frequency you want. > > Mark > > >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

I am using Leo Bodnar's GPSDO that is based on the 5328 and what looks to be a good TCXO as an external reference clock for a Perseus SDR. Using that, I measured phase noise and Allan Deviation of the best sources I have available and found the phase noise and Allan Deviation to be close to what has been measured on more expensive equipment. From a quick look at the 5351's data sheet it's jitter appears to be on the order of 100 times more than the 5328, and would result in unacceptable phase noise for my application. I would expect that the 5328 with the Thunderbolt as an input source would be even better than Leo's GPSDO. Note that the two outputs from the 5328 can't be two arbitrary frequencies, and I have found that different values of the various dividers can produce the same output frequency by varying levels of close in spurs. See my sites listed below for all the details: https://sites.google.com/site/perseusmods/ https://sites.google.com/site/perseusmods/home/performance https://sites.google.com/site/spectrumlabtesting/ 73, Mark W7MLG On Sat, Jan 20, 2018 at 6:59 AM, John Ackermann N8UR <jra@febo.com> wrote: > Hi Mark -- > > Thanks! To clarify, when you say you've found "it" acceptable, you're > referring to the 5328? > > What caught my eye about the 5351 was the three (or eight) outputs. My > idea was to build a board that would provide independent LO oscillators for > multiple VHF/UHF transverters. It looks like the 5328 has two outputs, > which is still useful but would require putting two or three of them on the > board. Which isn't the end of the world. > > Thanks, > John > ---- > > > On 1/19/2018 8:56 AM, Mark Goldberg wrote: > >> On Jan 19, 2018 6:01 AM, "John Ackermann N8UR" <jra@febo.com> wrote: >> >> 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? >>> >>> >> >> Datasheet states jitter in the 40-70 ps range. That is not very good. If >> you want something suitable for RF applications, look at the Si5328. It >> has >> jitter on the order of 300fs. >> >> I believe Leo Bodnar uses it in his GPSDOs and I can confirm the phase >> noise and Allan Deviation others have found and it is suitable for me for >> RF applications. It is not nearly as good as the Thunderbolt though. It >> will generate almost any frequency you want. >> >> Mark >> >> >> >>> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/time-nuts > and follow the instructions there. >