[TenTec] Noise from Fans

[Bob McGraw - K4TAX]

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.

73
Bob, K4TAX


----- Original Message ----- 
From: "K8JHR" <jrichards at k8jhr.com>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Friday, March 07, 2014 7:36 AM
Subject: Re: [TenTec] Noise from Fans


> Thanks for the uptake, Rick.
>
> Ah, yes... Heat.   I picked a really big resistor so I assume it is OK. I 
> will have to check it.  The guy who maintains our 17-site repeater system 
> specified the value for me.  I buy him lots of beer ...
>
> -----------------  JHR ---------------------------
>
> On 3/7/2014 4:07 AM, Rick - DJ0IP / NJ0IP wrote:
>> The resistor probably gets pretty hot.
>> The diode string does not.
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