[Collins] Boat Anchor Fans

[tim gorman]

A fan filter can only be effective for a cabinet with defined air inputs and 
exhausts. The exhausts must be designed to prevent dust migration into the 
cabinet when positive pressure is not applied to the cabinet by the fan. The 
cabinet must also be designed to prevent air from getting into the cabinet in 
place other than through the fan duct.

In the case of a Collins cabinet such as the 30L1, where dust can migrate 
into the cabinet in any number of ways, a fan filter is worthless. Whether 
you blow filtered air in or suck air out, dust will migrate into the cabinet 
from air flows through the sides, back, top, and bottom. Heck, with the fan 
not running, ambient air flows in the room will cause dust to filter into the 
cabinet over time. 

For the 30L1, it would seem that the prime benefit of the fan is to maximize 
the temperature differential between the tubes and the air surrounding the 
tubes. Get as big a fan as you can, run it as slow as you can, and move air 
by the tubes. You don't necessarily need a tornado, just a good steady flow. 
The result is going to be some dust in the cabinet. The solution to any dust? 
---- Forget the filters, just do a periodic cleaning of the interior. 

My preference was to put a fan on top of the cabinet and suck the hot air 
out. Hot air rises anyway so you get some efficiency from just pulling the 
hot, rising air on out of the cabinet and letting cooler air flow in from the 
bottom and the sides.

tim gorman ab0wr@arrl.net

On Thursday 17 April 2003 08:18 pm, Al Parker wrote:
> Dave,
> ? ? I beg your pardon -- every bit of air that goes out thru the fan has to
> be replaced by air coming into the cabinet. ?That air can also carry dust.
> Since it may be of lower velocity than the air passing thru the fan, it may
> not carry as much dust as it would if the fan was blowing in, but it will
> carry dust in.
> ? ? Unless Collins units have some special feature that I'm not aware of.
> 73,
> Al, W8UT
> New Bern, NC
> BoatAnchors appreciated here