[time-nuts] Re: DIY Low offset Phase Noise Analyzer (Erik, Kaashoek)

[Erik Kaashoek]

The oscillator I wanted to measure with the PNA (a cheap Chines TCXO) 
can now be measured with 30dB margin and the internal DOCXO is better 
than any other oscillator I have so I could say I'm done, apart from 
becoming a phase noise nut :-)
The whole build is still Manhattan style with long component leads so 
making a more compact build on a solid copper PCB may further improve 
performance.
@Ed:Â  The 7805 was temporarily replaced with a linear bench supply which 
made no visible difference
@Bob: The audio input I'm using claims to be 192kHz but in reality it 
stops at 96kHz so the upper limit is 48kHz for now, which is good 
enough. The calibration method you advised  (offset DUT) works very well 
now the gain is switchable.
Erik.

On 13-7-2022 18:54, Bob kb8tq wrote:
> Hi
>
> Well, obviously it’s now time to go get some better OCXO’s :) :) :)
>
> One further note: It is tempting to go to multi section lowpass filtering
> if you are trying to cover a range of frequencies. You also might try to push
> the range of the noise measurement up to higher and higher offsets. There
> is a point that all of this gets nutty. Peaking in the audio range is often the
> net result. Spice is one way to watch out for it. Sweeping the circuit is
> obviously a better way.
>
> Bob
>