bruce.griffiths@xtra.co.nz said: > The 16MHz is necessary for the loop to function: The mixer mixes down the > 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and > device noise is sufficient to start the process. > 10MHz = 26MHz - 16MHz > 16MHz = 26MHz - 10MHz What makes it stable at 10 and 16 MHz rather than 10.000001 and 15.999999? I'm assuming we are starting with a good 26 MHz crystal and that it would be hard to get filters that good. -- These are my opinions, not necessarily my employer's. I hate spam.

Hal Murray wrote: > bruce.griffiths@xtra.co.nz said: > >> The 16MHz is necessary for the loop to function: The mixer mixes down the >> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and >> device noise is sufficient to start the process. >> > >> 10MHz = 26MHz - 16MHz >> 16MHz = 26MHz - 10MHz >> > What makes it stable at 10 and 16 MHz rather than 10.000001 and 15.999999? > > I'm assuming we are starting with a good 26 MHz crystal and that it would be hard to get filters that good. > > > Asynchronous modes such as 10.000001MHz plus 15.999999 MHz can be problematic if the loop delay is too high. http://www.femto-st.fr/~rubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf <http://www.femto-st.fr/%7Erubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf> http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203 <http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203> http://tf.nist.gov/general/pdf/1800.pdf Bruce

There are also loop gain and phase shift requirements to be met for stable operation (ie with no asynchronous modes). Bruce Greg Broburg wrote: > 10.000005 = 26 - 15.999995 > > 15.999995 = 26 - 10.000005 > > This pair of equations is insufficient to define > that the ratio between these two frequencies > is exactly 1.6 : 1 or 1 : 1.6 > > There must be an additional concept here. > > Greg > > > On 4/9/2011 6:59 PM, Hal Murray wrote: >> bruce.griffiths@xtra.co.nz said: >>> The 16MHz is necessary for the loop to function: The mixer mixes >>> down the >>> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and >>> device noise is sufficient to start the process. >>> 10MHz = 26MHz - 16MHz >>> 16MHz = 26MHz - 10MHz >> What makes it stable at 10 and 16 MHz rather than 10.000001 and >> 15.999999? >> >> I'm assuming we are starting with a good 26 MHz crystal and that it >> would be hard to get filters that good. >> >> > > > _______________________________________________ > 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. >

10.000005 = 26 - 15.999995 15.999995 = 26 - 10.000005 This pair of equations is insufficient to define that the ratio between these two frequencies is exactly 1.6 : 1 or 1 : 1.6 There must be an additional concept here. Greg On 4/9/2011 6:59 PM, Hal Murray wrote: > bruce.griffiths@xtra.co.nz said: >> The 16MHz is necessary for the loop to function: The mixer mixes down the >> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and >> device noise is sufficient to start the process. >> 10MHz = 26MHz - 16MHz >> 16MHz = 26MHz - 10MHz > What makes it stable at 10 and 16 MHz rather than 10.000001 and 15.999999? > > I'm assuming we are starting with a good 26 MHz crystal and that it would be hard to get filters that good. > >

Bruce Griffiths wrote: > Hal Murray wrote: >> bruce.griffiths@xtra.co.nz said: >>> The 16MHz is necessary for the loop to function: The mixer mixes >>> down the >>> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and >>> device noise is sufficient to start the process. >>> 10MHz = 26MHz - 16MHz >>> 16MHz = 26MHz - 10MHz >> What makes it stable at 10 and 16 MHz rather than 10.000001 and >> 15.999999? >> >> I'm assuming we are starting with a good 26 MHz crystal and that it >> would be hard to get filters that good. >> >> > Asynchronous modes such as 10.000001MHz plus 15.999999 MHz can be > problematic if the loop delay is too high. > http://www.femto-st.fr/~rubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf > <http://www.femto-st.fr/%7Erubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf> > > > http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203 > <http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203> > > > http://tf.nist.gov/general/pdf/1800.pdf > > Bruce Additional references that estimate the degree of tank mistuning permissable before asynchronous modes occur: http://www.its.caltech.edu/~kaushiks/KS_RFIC.pdf <http://www.its.caltech.edu/%7Ekaushiks/KS_RFIC.pdf> http://www.its.caltech.edu/~kaushiks/KS_TCAS.pdf <http://www.its.caltech.edu/%7Ekaushiks/KS_TCAS.pdf> An early implementation: http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA457231 <http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA457231> Bruce

Bruce Griffiths wrote: > Bruce Griffiths wrote: >> Hal Murray wrote: >>> bruce.griffiths@xtra.co.nz said: >>>> The 16MHz is necessary for the loop to function: The mixer mixes >>>> down the >>>> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal >>>> and >>>> device noise is sufficient to start the process. >>>> 10MHz = 26MHz - 16MHz >>>> 16MHz = 26MHz - 10MHz >>> What makes it stable at 10 and 16 MHz rather than 10.000001 and >>> 15.999999? >>> >>> I'm assuming we are starting with a good 26 MHz crystal and that it >>> would be hard to get filters that good. >>> >>> >> Asynchronous modes such as 10.000001MHz plus 15.999999 MHz can be >> problematic if the loop delay is too high. >> http://www.femto-st.fr/~rubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf >> <http://www.femto-st.fr/%7Erubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf> >> >> >> http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203 >> <http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203> >> >> >> http://tf.nist.gov/general/pdf/1800.pdf >> >> Bruce > Additional references that estimate the degree of tank mistuning > permissable before asynchronous modes occur: > > http://www.its.caltech.edu/~kaushiks/KS_RFIC.pdf > <http://www.its.caltech.edu/%7Ekaushiks/KS_RFIC.pdf> > > http://www.its.caltech.edu/~kaushiks/KS_TCAS.pdf > <http://www.its.caltech.edu/%7Ekaushiks/KS_TCAS.pdf> > > An early implementation: > http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA457231 > <http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA457231> > > > Bruce > > If one needs a frequency comb: http://tf.nist.gov/general/pdf/2168.pdf Bruce