Do tube circuits have phase noise?
Do discrete components (solid state, transistors) in
coil and cap VFO circuits have phase noise?
Oscillators have phase noise. Properly designed -- with attention to
this -- the phase noise can be managed and made small. Crystal
oscillators are usually the cleanest, but they also have it to varying
degrees.
The worst are oscillators with improper gain using low Q components in
the frequency determining section. This is also a description of many
voltage controlled oscillators (VCOs) used in frequency synthesizers.
Early synthesizers used in Amateur radio products were often truly awful
in this regard.
The higher in frequency one goes, the harder it is to have low phase
noise close to the carrier being generated. Thus, it is generally
easier to have a certain amount of phase noise 500 Hz from the carrier
at 1 MHz than it is at 1 GHz.
This is part of the reason that many radios that feature up conversion
(for general coverage) have poorer phase noise than most radios that do not.
73,
Lyle KK7P
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