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

[Magnus Danielson]

Bob.

On 2022-07-13 23:32, Bob Martin via time-nuts wrote:
> Erik,
>
> I think you'd be better off  with dual supplies and take advantage
> of the amplifier PSRR. I'd put a reverse Schottky diode to ground at
> the output of each regulator to ensure startup. On some regulators,
> a reverse voltage on the output can inhibit regulation. There is
> a lot to be said for a ground reference that is a ground plane as 
> opposed to some floating reference voltage when worknig with low 
> signal levels...

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.

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.

Cheers,
Magnus