[time-nuts] Phase noise measurement with a sound card

[Bruce Griffiths]

Steve Rooke wrote:
> Bruce,
>
> 2008/12/17 Bruce Griffiths <bruce.griffiths at xtra.co.nz>:
>   
>> You can easily cobble one together using whatever sound card your PC has
>> together with a mixer and a few inexpensive opamps, filters etc.
>>     
>
> I have read all your posts with great interest and have learned a
> great deal from them but the thing that is invarably missing is a
> reference to any actual designs. Do you have some links that would
> enable a complete idiot like myself to be able to do things such as
> this please. I am keen to be able to achieve these things, as I am
> sure others are as well, but I lack the sort of hand-holding to get
> into this field.
>
> Thank you,
> Steve
>   
Steve

Wenzel's site indicates how phase noise measurement of an OCXO can be done:

http://www.wenzel.com/documents/measuringphasenoise.htm

However he doesn't discuss the simpler problem of measuring the phase
noise of components such as amplifiers.
This only requires a single low noise signal source and the phase lock
loop can be replaced by a phase shifter.

You will need:

1) A sound card

2) Spectrum analyser software for the sound card

3) A low noise preamp

4) A mixer/phase detector

5) A phase shifter

6) A passive splitter

7) Some RF low phase noise isolation amplifiers

8) A means of calibrating the entire phase noise measurement setup.

You need to first obtain suitable software
For Linux Baudline will suffice if you only have a 16 bit sound card.
You can also run spectrum Lab under Wine

For Windows (but not Vista unless you run XP in a virtual machine)
Spectrum Lab is suitable.
http://freenet-homepage.de/dl4yhf/spectra1.html

The first task is to install suitable software and become familiar with
the performance of your sound card.
Once this has been determined you will be ready for the next step.

To be continued........

Bruce