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Hi Al,

Find here my modest and noisy experiments under the nick name ALZ, sorry it's in French :

Half of the parts come from recycle i.e. : transistors, shield, epoxy breadboard, battery connector ...
The first transistor in reverse biasing acts as a Zener diode, this is actually the noise source, you may try some NPN transistors to find a noisy one, better with an oscilloscope you can see the starting voltage of noise (Zener bend), the reverse voltage should be about 9V ...

The noise is detected from few KHz to 1GHz upper limit of my USB dongle, sure it's not very flat or calibrated like a professional one but it's not too bad for a one pound source.

I hope it can help someone.