Simple True White Noise Generator

[phenol]

that's a service monitor with a spectrum analyzer function, among other things.no idea how much an operational unit would cost (<1k?), but the R&S analyzer above with all options included (preamp, tracking gen, various software licenses for wimax,bluetooth,wifi, etc analyses) easily exceeds EUR20-25k, and that's just their general purpose model. i ordered the preamp option separately for eur1100. it will drop the noise floor to <-160dbm

they demonstrated their newest emi full compliance test receiver+real time specan, a fine looking and working windows-based (just like the small analyzer above) instrument, with a prohibitive starting price tag of eur50k+
im quite happy, though, as they left one of their 6GHz demo units to play with until our own arrives. and now we have two

i will build the noise source above, but im somewhat reluctant to connect those 100u capacitors making powerful transients at powerup/down to the delicate frontend of the analyzer. an attenuating/matching resistor pad will keep power levels within safe limits

 

[Sigurthr]

The 100uF are for good low freq response, you could simply scope the output of the npn pair if you don't mind a bit of DC offset.

 

[phenol]

scoping high Z sources with a 50-ohm instrument would skew the measurement results, therefore some matching is in order...ideally, i would probe the low impedance output of lm386 to see the roll-off of both the fet amplifier and the power amp itself, but for some reason im unable to recall where i put those lm386s.
instead, i'll stick an emitter follower after the mosfet and post pics as soon as i find some time.