[TenTec] Noise from Fans

[K8JHR]

Ah... so the "plot sickens..."        ;-)

Thanks for that further gloss.  I gotta learn more about diodes.

A local Elmer told me to make a voltage divider (like an L-pad 
attenuator) if I wanted to assure a predicted voltage drop, whereas 
using one resistor was not as predictable.  This parallels what you are 
saying here.   This is why I used an L-pad attenuator in my microphone 
matching circuit, but also explains why I used a single resistor in 
knocking down the bias voltage - I was not as concerned about the 
accuracy of the result on that aspect, where I was on the mic attenuator 
bit.  Now I will have to learn about how diodes might be used...  new 
horizons for me.

-----------------  JHR ------------------------


On 3/7/2014 8:51 AM, Bob McGraw - K4TAX wrote:

> Typically a silicon diode has about 0.7 volt drop per unit.  Thus two
> diodes in series would drop 1.4V and three in series would drop 2.1
> volts etc.  The advantage of using a diode over using a R has to do with
> constant voltage drop using a diode where a fixed R will have different
> voltage drop values depending on current demands.  Some fans may have a
> higher starting current than running current.  With a critical value of
> R one could experience a condition where the fan won't start due to the
> IR drop.  This problem won't exist with a diode string when used as a
> voltage dropping method.
>
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