[CQ-Contest] Amplifier venting

[Tom Rauch]

> >ducting run above my drop ceiling, then out to the garage where the
> >fan can be mounted.  Hopefully this would dramatically cut down on
> >the=20 shack noise, having the fan so far away. =20
> >
> >Any experiences you've had, or ideas that you have would be greatly
> >appreciated so I don't end up re-inventing the wheel! :-)
> >
> >73...Scott

Scott,

You might get away with an exhaust fan drawing on the vents, but 
I'd either measure cabinet temperature rise or air pressure 
differential from inlet to outlet on the PA to be safe. 

As a general rule it is far better to blow pressure into the restriction 
with a blower than draw air out of the restricted area with a fan or 
blower.

While a blower can pressurize quite nicely, it does not draw air 
very well at all. Neither does a fan. A small amount of inlet 
pressure increase will result in much higher static pressure on the 
outlet (it actually acts like the blower has "gain"); while even a 
slight restriction on the inlet reduces airflow and pressure on the 
outlet a much larger amount than you might expect.

Whatever you do, be sure to watch cabinet temperature rise on the 
outlet side of the air system or measure airflow.
73, Tom W8JI
W8JI at contesting.com 


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