Said, What tool(s) did you use to generate that data and output the graph?
Thanks, John On Fri, Oct 17, 2014 at 6:10 PM, S. Jackson via time-nuts < time-nuts@febo.com> wrote: > Jim, > > Here is the resulting 10MHz phase noise plot from the 20MHz TCXO output: > > > In a message dated 10/17/2014 11:32:49 Pacific Daylight Time, > saidj...@aol.com writes: > > > Hello Jim, > let me answer through Time Nuts as this may interest other parties as > well. > Yes, using a fast flip flop to generate 10MHz out of the 20MHz TCXO 3.0V > CMOS output from the LTE-Lite module will preserve the phase noise > (actually > improve it by up to 6dB due to the 20log(n/m) noise improvement) and will > not add any spurs if you use the clean 3.0V output from the LTE-Lite > module > or an external clean power supply (please note the LTE-Lite TCXO RF output > is 3.0V due to the internal 3.3V to 3.0V Low Noise regulator feeding the > TCXO and buffer). > Use fast logic such as 74AC74, 74FCT74, or the like. We do exactly that on > our ULN-2550 boards to generate 50MHz and 25MHz out of the 100MHz, and > using a fast CMOS divider will result in additive phase noise that will be > below the crystal oscillator phase noise floor. > That will result in significantly better phase noise and much lower spurs > than using the synthesized 10MHz output from the board, and one 74' chip > can generate both 10MHz and 5MHz out of the 20MHz LTE-Lite output. This is > exactly what we would do here if we needed a clean 10MHz from the 20MHz > LTE-Lite board. > I believe you can order low-noise divide-by-2 blue-top boxes from Wenzel > already packaged-up and connectorized as well. > Hope that helps, > Said > Hi Said > I was one of those looking for 10Mhz but I just thought again now that it > might be just as well to divide the standard 20Mhz output by 2 using a FF. > I think that would preserve all the desirable characteristics of the 20Mhz > signal which I understand to just be square wave at CMOS 3.3v levels > anyway. Is that correct? > Thanks > Jim > > > _______________________________________________ > 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. > _______________________________________________ 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.