[time-nuts] RF Mixers for oscillator comparison

Arnold Tibus Arnold.Tibus at gmx.de
Sun Apr 19 22:04:57 UTC 2009

On Mon, 20 Apr 2009 09:03:36 +1200, Bruce Griffiths wrote:

>Corby Dawson wrote:
>> Arnold,
>> Look at the top of page 3 on the link below. Not sure how they arrived at
>> their conclusion but there is one opinion on the HP mixers!
>> http://www.unusualresearch.com/AppNotes/TimeNuts/OptDualMixer.pdf
>> Corby Dawson
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>Statements about the low flicker noise of these mixers are sprinkled
>throughout the phase noise literature.
>Someone must have measured the phase noise of these and other mixers at
>some time.

>Its relatively easy to measure mixer phase noise:
>All one needs is a low noise preamp plus a sound card a 90 degree hybrid
>(or a suitable length of coax and a splitter) and a low noise source.

>However NIST papers often include a phase noise plot (attached) that
>illustrates that high level mixers can have a significantly lower phase
>noise than low level mixers (like the HP10514A).
>When choosing a mixer for this for phase noise measurement applications
>one may actually need to measure the phase noise characteristics of
>candidate mixers.


Wow, a good overview, Bruce! 

But remain the questions: 
which are these high level mixers, are they readily available? 
Are they affordable? 
Perhaps not, why are they then not applied more often?


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