On 4/12/17 1:23 PM, Bob kb8tq wrote:
Hi
*All* incandescent lamps emit RF ….. They are a resistive device that is heated
to well above
room temperature. People do use them in simple noise figure meters. The
inductance of the
filament in a typical bulb restricts the bandwidth a bit. The are designs from
at least the 1960’s
running around. I suspect the approach is much older and that’s just when I was
introduced to
the technique (= built one).
The advantage of the diode noise source (a typical one is 7000K, a bit
higher than a 3200K incandescent bulb) is that it's more stable - the
temperature of a lightbulb filament depends on a lot of things - and
that it can be "hotter"
A 15 dB ENR noise source is something like 9500K - that's a lot hotter
than something incandescent, and well above the 3700K melting point of
tungsten
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