In article ,
says...

That depends on your filter. If you're trying to design a high pole
count filter with really steep skirts and you want to verify it's final
rejection then yes, you need a low phase noise oscillator. This is
probably why he has "low noise" in his title.

Perhaps, but if you want to verify final rejection, you want much wider
tuning range than you're going to get from a pulled crystal. A 100 Hz-
wide filter might be -100 dB down at 5 kHz but -50 dB down at 50 kHz,
and if you care about that, you need to be able to look farther away
from the carrier.

His desire for a narrow-range source made me think he was more
interested in shape-factor and ripple alignment than ultimate rejection.

Maybe he can use two different oscillators to get the best of both
worlds. A high-quality LC oscillator is actually pretty darned quiet at
large offsets from the carrier. I think it was Tom Bruhns, or one of
the other HP guys at least, who once pointed out that the old HP 608-
series boatanchors were quieter at 100 kHz offsets than the flashy,
high-dollar synthesizers that followed them.

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------