[volt-nuts] Practical power supply noise testing

Brooke Clarke brooke at pacific.net
Fri Jul 1 17:39:41 EDT 2016

Hi Poul

When testing VCOs any noise on the control voltage causes a frequency change in the output which can be characterized.
The HP/Agilent 4352 VCO tester contains a programmable DC supply with exceptionally low noise.

Instead of headphones something like the HP 4395A which has a spectrum analyzer mode with a true RBW of 1 Hz to allow 
displaying root(Hz) noise levels (true I&Q detection rather than the old analog peak detection). 
http://www.prc68.com/I/4395A.shtml <http://www.prc68.com/I/4395A.shtml>

AFAICR there were some HP app notes on measuring power supplies which may have included noise.

Have Fun,

Brooke Clarke
The lesser of evils is still evil.

-------- Original Message --------
> --------
> In message <2656F010-8E12-4BAD-B9AE-713CEFEE1B0A at febo.com>, John Ackermann N8UR writes:
>> I have several supposedly low noise bench power supplies that I want to check out.  They seem to work well but are quite old, so of course one wonders about the caps, etc.
>> Can someone suggest a practical test regime to verify power supply
>> DC noise performance?  Preferably one that doesn't require building
>> up custom low noise amps?
> Listen to them ?
> All the "hard" noise is in the audio-range, so a series capacitor
> a low-noise amp and a pair of headphones...

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