[R-390] Alternative to IERC tube shields?

[rbethman]

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.

Bob - N0DGN

2002tii wrote:
> Definitely a big improvement.  But where do you find these "quiet 
> brushless fans"?  I guess quiet is in the ear of the behearer.  In my 
> view, all the cooling fans I've ever met are "quiet" only when 
> evaluated in a small room with a window air conditioner running.  I 
> generally use oversize fans and slow them way down to reduce the noise.
>
> A noiseless option is to build a chimney about 3-6 feet tall (~ 1-2 
> meters for the metrically inclined) that is fed from vents in the top 
> or top-sides of the radio, leaving appropriate bottom and/or 
> bottom-side vents for air intake.  Give thought to the 
> convection-driven air circulation.  Sometimes, one needs to block off 
> some vents and/or make some new ones.  Typically, the chimney for a 
> 390 or SP-600 would be 30-40 square inches in cross-section.  I build 
> them out of corrugated box cardboard, with shallow pyramidal 
> transitional sections. You'd be amazed by how much air such a thing can move.
>
> Best regards,
>
> Don
>