[time-nuts] distribution amplifier

[John Ackermann N8UR]

Hal Murray said the following on 08/26/2006 03:39 PM:

>>That's interesting.  The MAX477 video amp that is used in the TADD-1
>>(http://www.tapr.org/kits_tadd-1.html) does a lot better than that.
>>Here is a phase noise plot of the TADD-1 at 10MHz; it is better than
>>-105dBc at 1Hz and reaches a noise floor of -142dBc at less than
>>100Hz. 
> 
> 
> Where does that sort of noise come from?
> 
> Power supply ripple?  Ground loops?  Other mechanisms?

There are lots of possibilities, but one is just the intrinsic noise in
the amplifier; IC amplifiers are usually spec'd in terms of nV of noise
per root-Hertz.  Another contributor can be noise on the power supply,
both broadband and power-line related.

By the way -- the HP 5087A distribution amplifier is spec'd to be
-145dBc at >1kHz (measured at 5MHz); I'm frankly surprised that the
broadband TADD-1 is so close to that.

John