Agreed.  Plus, a constantly-operating fan pulls a lot of dust and dirt into
the equipment.  Besides, the fan is ineffective until the heat sink gets
warm, so starting it immediately upon key-up is a waste of energy.  In my
opinion, a snap-action thermal switch mounted on a heat-sink fin is the
simplest and most practical means of controlling a fan.  I use a switch that
turns on the fan when the heat-sink reaches 120 degrees F and stays on until
the temperature drops to about 90 degrees.  My preference is a switch sold
by Digi-Key as Catalog Number 317-1094-ND.

73, Eric Lemmon WB6FLY
 

-----Original Message-----
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of skipp025
Sent: Wednesday, December 23, 2009 8:24 AM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Re: Henry Amps

  


> >The question is... do the fans run all the time or do they
> >turn on with temperature or keyed with RF or an external
> >logic (PTT) line?
> >
> >It's pretty bad listening to fans whining at a radio site
> 
> A spinning fan is a working fan. Also kind of hard for a 
> mouse to build its nest in a spinning fan.

A constant spinning fan makes unnecessary noise, consumes 
energy and wears out much faster. If there's a mouse in 
the works, chances are they most often migrate toward warm 
parts in the power supply section and you'll have a much 
bigger program down the line. 

"Bite Blocks" for the Mouse and all will be quiet... 

s.

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