> > Do crystals vary in the amount of random phase noise
> > produced in or by a typical crystal oscillator / FM
> > modulator circuit as used in a typical repeater
> > transmitter?
> > Do crystals vary in produced FM (phase) noise.
Yes, but I would not label the noise as phase noise.
> If the answer is yes, Which crystal manufactures
> make quiet crystals
Crystals within the same mfgrs shipment can often
differ quite a bit. Most all mfgrs make high spec
crystals. When you depart the most common mfgrs
specs, you wallet goes along for the ride.
> > and just how does one insure that he gets this
> > need across to a crystal supplier?
You would have to spec a specific crystal type or
design cut / application, costing a more money.
Practical options are trying multiple combinations
of different channel elements and crystals in the
same circuit.
I've not found the mentioned noise floor to be a big
problem when <200Hz. In high spec applications, the
easy fix is to order multiple xtals and place them
in different lot channel elements. Most of the time,
the xtal - channel element combination works just
fine.
There is a typical 1 out of 10 or 15 tx packages,
which seems to have a relative higher noise level.
Sometimes moving the xtal to a different element
works... sometimes it doesn't. I have also seen
various brand channel elements, which seem to be
more problematic than others.
If you're bothered by the amount of the noise,
simply order and try a second xtal/channel element
package. I've never had to go past a second try.
cheers
skipp025 at yahoo.com
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