More to do with amateurs using narrow band modulations, and the LB GPSDO being moderately good close in. Phase noise out beyond a few kHz goes more or less unnoticed on SSB
Andy www.g4jnt.com On Wed, 31 Mar 2021 at 13:35, Dana Whitlow <[email protected]> wrote: > Chris, > > It may be that the modulation and subsequent demodulation scheme used for > satellite TV and the > like is rather more robust than many people give it credit for. > > Dana > > > On Wed, Mar 31, 2021 at 7:09 AM Chris Wilson <[email protected]> wrote: > > > Hello everyone > > > > Monday, March 29, 2021 > > > > Thanks for the replies, some went a little over my head, which is not > > hard :) I am wondering how people successfully use a Leo Bodnar > > programmable GPS source to provide an external LO for an LNB as opposed > to > > its internal xtal. What is different, in simple terms please, between my > > Ublox output and the Leo Bodnar one? > > > > > > Best regards, > > Chris mailto:[email protected] > > > > > > LJ> On 3/29/21 10:14 AM, John Ackermann N8UR wrote: > > >> That's probably a really bad idea. The phase noise from the TIMEPULSE > > >> output is pretty bad compared to a "real" RF source, and by the time > > >> it's multiplied up to 10 GHz you'll have more noise than signal. > > >> Attached are some phase noise plots and a couple of spectrum analyzer > > >> captures to give you some idea what to expect. > > > > >> BTW, even the Bodnar unit may not look too good at 10 GHz -- remember > > >> that you increase phase noise by 20 dB for 10 times multiplication. > > > > >> John > > > > LJ> What's the signal bandwidth from Es'Hail? > > > > LJ> The optimum strategy is a *very quiet* crystal oscillator that you > > LJ> discipline with the 1pps, and choose that oscillator so its frequency > > is > > LJ> what you need. > > > > LJ> What we've done in the past is use the reference to clock a NCO in > > FPGA, > > LJ> and use one of the well known spur reduction techniques that pushes > the > > LJ> spurs away from the center before running it to the DAC. This > degrades > > LJ> the performance at, say, 100kHz away, but improves the performance > > LJ> within 1 kHz. This relies on knowing what the loop bandwidth is in > your > > LJ> 10GHz LO PLL, since inside that bandwidth it's the reference, but > > LJ> outside it's the DRO or GaAs oscillator. > > > > > > LJ> There might be some DDS chips that implement this kind of thing - the > > LJ> latest chips from ADI are pretty sophisticated. > > > > > > > > > > > > >> On 3/29/21 12:25 PM, Chris Wilson wrote: > > > > > > >>> 29/03/2021 17:20 > > > > >>> Can I use my Ublox NEO-M8T-0-10 as a LO for a modified satellite > > >>> LNB on 10 GHz? It needs 25 MHz and the Ublox is my only GPS locked > > >>> source for such a frequency. I want to receive the Es Hail downlink > > >>> with excellent stability. I can lock the receiver to 10 MHz which is > > >>> available from my Trimble Thunderbolt. If the Ublox would do I would > > >>> not have to buy something like the Leo Bodnar GPS. Thanks. > > > > > > >> _______________________________________________ > > >> time-nuts mailing list -- [email protected] -- To unsubscribe > > send an email to [email protected] > > >> To unsubscribe, go to and follow the instructions there. > > > > LJ> _______________________________________________ > > LJ> time-nuts mailing list -- [email protected] -- To > > LJ> unsubscribe send an email to [email protected] > > LJ> To unsubscribe, go to and follow the instructions there. > > _______________________________________________ > > time-nuts mailing list -- [email protected] -- To unsubscribe > send > > an email to [email protected] > > To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send > an email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
