[Drake] Cooling fans - blow in or out?

[Bob Camp]

Hi

Regardless of weather they blow in or out fans do aggravate a basic 
cooling problem. Dust and lint are pretty good insulators. Depending on 
the situation in your shack (I have a couple of large lint sources 
known as dogs ...) the stuff may build up faster or slower.

As the stuff builds up on parts and surfaces the cooling process slows 
significantly. I have never popped open a piece of fan cooled gear that 
was not full of dust. That's true weather it's been around here or 
picked up at a flea market. It's also true of most of the gear at work. 
Dust packed filter screens are a common thing ....

I rarely see convection cooled gear as full of crud as fan cooled gear. 
The process simply does not work quite the same way with convection. 
You have to get up above a minimum feet per minute rate to pick up and 
move dust and stuff. Unless you are running a convection blast furnace 
the fpm simply are not there.

Should we give up on fans? No, of course not. The fan even running at 
quarter speed is enormously more effective at moving heat than 
convection. You can easily verify this with a simple finger touch test 
with and without the fan. No massive IR scanners required ...

If you go with fan cooling then you need to do some PM with an air hose 
on a regular basis. Wish I could tell you that I'm as good at the PM as 
I am at talking about it, but I'm not. Dusting and vacuuming just isn't 
very high up on the list of fun things to do ....

	Take Care!

		Bob Camp
		KB8TQ