[time-nuts] RF Mixers for oscillator comparison

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Apr 19 21:03:36 UTC 2009


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
> ____________________________________________________________
> Debt collectors calling your house?  Click here to consolidate into one payment.
> http://thirdpartyoffers.juno.com/TGL2141/fc/BLSrjpTIk3l9oQnolYGEY40TVwmsBD4opDDeVSRG36KHWHhZWexSiuRrXdm/
>
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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.

Bruce
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