[R-390] Alternative to IERC tube shields?

[2002tii]

Bob wrote:

>And while I haven't done any testing to prove it, I would
>think that adding a bit of forced convection cooling would help a lot.
>Thanks to cheap and quiet brushless muffin-type fans it is easy to try
>at least.

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