[R-390] Synthesizer Phase Noise

[Shoppa, Tim]

N0DGN writes:
> When you use an antenna system(s) like this, noise becomes a non-issue.  

Like others have remarked, you are confusing front-end noise with phase noise.

The evilness of phase noise, is that it makes signals near but not at the desired frequency, appear as noise in the passband.

Much ham and a lot professional equipment from the past few decades has phase noise that can be heard by tuning adjacent to a strong CW signal and hearing the noise pulsing on and off. They also transmit this phase noise too (although that becomes "somebody else's problem" in the perspective of an individual ham, in actuality it becomes everybody's problem.)

The best ham equipment from the past several years, this is not so much of a problem. It is still measurable and very real and can become noticeable under the most extreme conditions (e.g. contest weekends).

The synthesizer designs of the 50's and 60's military equipment that I'm aware of, is of a mix-divide mechanism, and AFAIK did not have the exactly the phase noise evilness that many of the 80's and 90's ham rigs suffered from. These military synthesizers are characterized by by rotary digit selectors for each decade, mixers, and divide by ten circuits for each decade, and mixers for each decade. This technique is very hardware intensive but comparatively clean compared to most simple PLL's and DDS's. 

Tim.