[time-nuts] RF Mixers for oscillator comparison

[Bruce Griffiths]

Arnold

They do have lower isolation than the phase detectors and the TUF mixers.
However it would be well worthwhile measuring their dc offset, its drift
and their phase noise.
Its possible to mitigate the effects of lower isolation by using low
phase noise isolation amplifiers.

If you do this please make it available so that it can be used by others
in making similar decisions.

It would be useful if anyone else who can measure the phase noise of any
mixers they have do so.
In this way we can build up information on the phase noise performance
of various mixers without having to purchase mixers for such measurements.

Bruce

Arnold Tibus wrote:
> Bruce,
>
> Are such as
>  SRA-1H or SRA-3H no possible candidates?
> Such I have still somewhere in a drawer.
>
> Arnold
>
> On Mon, 20 Apr 2009 10:25:28 +1200, Bruce Griffiths wrote:
>
>   
>> Arnold
>>     
>
>   
>> Some of the early equipment produced by NIST used mixers from a company
>> that eventually became into Minicirucits.
>>     
>
>   
>> Suitable candidates from the Minicircuits range are:
>>     
>
>   
>> TUF-1H+:
>> http://www.minicircuits.com/pdfs/TUF-1H+.pdf
>>     
>
>   
>> This mixer doesnt have isolated RF, LO and IF grounds so external
>> transformers would be rrequired.
>> It  does have somewhat higher port to port isolation than most mixers.
>>     
>
>   
>> The minicircuits phase detectors such as:
>>     
>
>   
>> http://www.minicircuits.com/pdfs/RPD-1+.pdf
>>     
>
>   
>> http://www.minicircuits.com/pdfs/MPD-1+.pdf
>>     
>
>   
>> are worth considering, at least they have separate RF and IF grounds, a
>> high maximum output as well as low dc offset and offset drift.
>>     
>
>
>   
>> All of these are below $US25 (at the source).
>>     
>
>   
>> The phase detectors are perhaps the safest option however measurement of
>> their phase noise would be advisable.
>>     
>
>   
>> Bruce
>>     
>
>   
>> Arnold Tibus wrote:
>>     
>>> 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
>>>>> ____________________________________________________________
>>>>> 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
>>>>     
>>>>         
>>> 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?
>>>
>>> Arnold
>>>
>>>
>>>
>>>
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>>>       
>
>
>   
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