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

[Erik Kaashoek]

Bob,
You may have explained this before but I still do not understand.
Does the phase modulation slope at the detector depend on the depth of 
the phase modulation? I think not.
With 57 degrees one should get an output voltage that is to be regarded 
as the 0dBc level but this can not be measured due to the high gain in 
the audio path.
When you reduce the modulation depth with a factor 10 the measured 
output voltage should decrease with 20dB.
Modern digital signal generators are supposed to provide phase 
modulation with at least 0.01 degree accuracy.
So it could be possible to measure the phase detector slope with 0.57 
phase modulation depth by measuring what should be -40dBc
Or, if the gain is very high, less accurate with 0.06 phase modulation.
Or am I making a mistake in my reasoning?
Erik.


On 8-7-2022 3:57, Bob kb8tq via time-nuts wrote:
> Hi
>
> One consideration:
>
> If you do signal injection for calibration, you have the amplitude uncertainties on
> both the “carrier” and injected signals. The slope at zero on the beat note is likely
> to be *much* more accurate ( even if gain measurement at audio gets thrown in …)
>
> Bob
>