[time-nuts] Re: Dual Supplies for Low Offset Phase Noise Analyzer

[Erik Kaashoek]

Magnus,
See below

On 14-7-2022 14:50, Magnus Danielson via time-nuts wrote:
> I am in full agreement. While there is a certain pain in doing it, but 
> it removes a long set of issues relating to not having it. I've had 
> that standpoint from the start, but felt that Erik may benefit from 
> getting a lot of the other things going first and learn from it, as he 
> seemed so negative about it. It is only when one sees the alternative 
> cost that one can make the correct decisions. However, when trying to 
> fix many things, it can take time to spend on all the things, so 
> spreading things out a bit in time can serve it's purposes. This not 
> to be disrespectful to Erik, rather the opposite. Then again, 
> sometimes there is a different balance that pans out for it's purpose.
No offense taken!!
Unfortunately I'm the type of person that learns most by making 
mistakes. So I first wanted to try to get the single supply working as 
the PNA is not getting its own permanent supply. Performance at 10kHz 
offset is now at the -155dBc/Hz noise level, although still with a lot 
of mains harmonics but these could also come from the not so good audio 
cable connecting the PNA and the Audio input or a ground loop.
Replacing the single supply with a triple supply is still to be tested.
>
> I'm setting up measurement rig myself and it starts of with +5V and ± 
> 15V. Luckily I have a spare supply delivering exactly that, will just 
> check that it is reasonably in good condition.
>
> There will be a challenge of getting all the pieces fit together, but 
> I'll slam a RPi4 to it and see how that works out.
>
> I've realized that I should be doing a input level measure and 
> programmable damper. Wonder if someone already have nifty small boards 
> for that
As long as you want check for any level above +7dBm a simple rectifier 
will do in combination with an analog input of the RPi
Erik.