In article , Tim Wescott
writes:

John Miles wrote:
In article ,
says...


A DDS isn't going to have good enough phase noise. The OP is correct in
using a pullable crystal oscillator.


Eh? He wants to sweep a filter. You don't particularly care about
phase noise when you do that.

-- jm

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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.

The "need" for low-noise RF sources was prompted by the
electronics industry going hot and heavy on cellular telephony
which uses partly phase demodulation and clock recovery
circuits in digital electronics. Because of those particular
markets, "low noise" has become a Big Buzzword.

Whether you have one pole or twelve or whatever, you will
NOT need a specific "low noise oscillator!" The very ordinary
sweep oscillators of ten, twenty, or thirty years ago are quite
fine.


retired (from regular hours) electronic engineer person