[R-390] Alternative to IERC tube shields?

[mikea]

On Mon, Aug 17, 2009 at 12:30:33PM -0400, rbethman wrote:
> A source for quiet muffin fans would be from an older computer for 
> scrounging purposes and method.
> 
> The SPECIFIC one I have in mind is the CPU mounted fan - NOT - the power 
> supply fan.
> 
> If you cannot scrounge and are forced to purchase, try Office Depot, or 
> if you must, a computer store that sells mother boards, CPUs, and the rest.
> 
> These will be 12 V.
> 
> The typical brushless type muffin fans that most of us use are indeed 
> the 4" X 4" (approx), 120VAC fans that "normally" scream.  One puts a 
> large sand encapsulated resistor in the hot leg feeding it.  The dropped 
> voltage provides a BIG drop in RPM, and works wonders in quieting it 
> down.  I've added these to transmitters and receivers.

An alternative is to put two of these in series; this also drops the RPM
nicely, but since you have two fans, you're moving twice as much air and 
not having to put up with the heat from the resistor. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin