John Larkin wrote:
On Wed, 11 Jan 2006 10:08:19 -0800, "RST Engineering"
wrote:

A hot resistor.

How about a thermistor or a lamp filament that was 50 ohms at some
high temperature. You could heat it with DC, sense its
resistance/temp, and let it make noise, all in a single part.

Old vintage noise figure meters used gas tubes. And I think there was
a pencil tube that mounted in a waveguide and made shot noise.

And, of course, the old photomultiplier trick.

I still like the flashlight/photodiode trick. You can get a really good
calibration just from the dc, and can calibrate the frequency response
with a spark plug.

Cheers,

Phil Hobbs