Phase noise in PLLs is impacted by the VCO as was
stated and also impart by it's sensitivity, the number of
millivolts per kilohertz of frequency change. The other
major factors include loop filter and division ratio. There
are also various pll design topologies which impact noise
both directly and indirectly by division ratio. There is quite
a bit about this in the ARRL handbook and from various
chip designers such as Analog Devices. AD has a free
program to calculate phase noise and other PLL
characteristics for their chips.
R
On 5 Nov 2004, at 12:55, Martin Ewing wrote:
> Cheap PLLs, yes. A lot depends on the quality of the
> controlled oscillator. You can use a PLL to steer a
> crystal oscillator (oh so gently), and get minimal
> phase noise. Effectively, the crystal filters the
> noise sidebands. It could be a lot better than the
> excellent Orion VFO, for example, which has to work
> over a wide frequency band.
>
> 73, Martin, AA6E
>
> p.s. I guess this confirms Dave's later note, FWIW!
>
> --- David McClafferty <ve1adh@yahoo.ca> wrote:
>
> > I am only going by what I have experienced and read,
> > PLL's produce more phase noise than xtals
> > oscillators.
> >
> > Dave, VE1ADH
> >
> > --- John Clifford <johnclif@ix.netcom.com> wrote:
> > > > But why would you want to do it? Changing to a
> > PLL
> > > will
> > > > increase the phase noise.
> > >
> > > Are you saying that having PLL control over the
> > BFO
> > > xtals would increase
> > > phase noise?
> > >
> > > How?
> > >
> > > - jgc
> > >
> > > John Clifford KD7KGX
> > >
> > > Elecraft K2 #1678
> > > /KSB2/KIO2/KBT2/KAT2/KNB2/KAF2/KPA100
> > > Ten-Tec Omni VI/Opt1, Centaur, 238B
> > > Alinco DR-605TQ, DJ-V5
> > > Icom T90A
> > >
> > > IRLP #3978
> > >
> > > email: kd7kgx@arrl.net
> > >
> > > _______________________________________________
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> > >
> > http://lists.contesting.com/mailman/listinfo/tentec
> > >
> >
> >
> ______________________________________________________________________
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