[time-nuts] noise sources Re: Re. DIY atomic "resonator"
kb8tq at n1k.org
Wed Apr 12 21:33:34 EDT 2017
Back in the day (1960’s) noise diodes were quite a bit more expensive than they are today. Even
today, a miniature lightbulb is quite a bit less expensive than a noise diode. You don’t go that way
because it’s better. You go that way because it’s cheap ….
> On Apr 12, 2017, at 7:04 PM, jimlux <jimlux at earthlink.net> wrote:
> On 4/12/17 1:23 PM, Bob kb8tq wrote:
>> *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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