[Elecraft] Thermal control for Q1 / Q2 in KPA100?

[Tom Hammond]

Don, et al:

I've now placed the PDF of my KPA100 Cooling Fan Enclosure on my web 
site (www.n0ss.net). The PDF is located in the "K2 Specific Files" 
section of the page, about 3/4 of the way down the page.

The fan shown in the illustrations came from a CPU cooler.. It's much 
smaller than most PC cooling fans, but just about anything will work 
pretty well is seems. The PDF contains hole cutting and drilling info 
for both 92mm and 80mm square muffin fans. I originally had an 80mm 
square fan installed, but when I scavenged the tiny CPU cooler fan, I 
installed it using a cover plate which mounted in the 80mm fan mounting holes.

I have two fan speeds... The low speed suffices for about 90% of my 
operation and the higher speed is used when I'm contesting and want a 
bit more cooling. The KPA100's fan seldom comes on, and when it does, 
it's on for a very short length of time... and everything(!) stays 
nice 'n cool.

The cooling enclosure is low profile and extends all the way to the 
back of the KPA100 heatsink, so cool air is drawn over a large area 
of the fins. Additionally, the enclosure extends just ahead of the 
front of the heatsink, so it draws air OUT of the K2 case via the 
vents in front of the heatsink (vents actually 'made' by the heatsink 
and the cover plate just ahead of it).

73,

Tom   N0SS


At 08:38 AM 12/6/2006, Don Wilhelm wrote:
>Tom,
>
>Yes, we should all see what you have created.  How about a photo and a short
>note on your website (no need for a .pdf file IMHO).  Such an addition is
>great for those running digital modes and is nice to have when operating hot
>and heavy during a contest.
>
>As you have pointed out, it is important that the fan moves air upward so it
>aids the flow from the internal fan rather than blowing air onto the heat
>sink. Just laying a muffin fan on top of the heat sink is effective as a
>'quick and dirty' solution, your plenum sounds like a great permanent
>addition for those instances where there is not a lot of free-air space
>above the K2/100.
>
>The fact that an exhaust fan flow cools objects better than blowing air onto
>a surface is a bit counter-intuitive because standing in the downstream side
>of a fan feels cooler to the skin - but that is only because of evaporation.
>Careful measurement will show that the cooling effectiveness for an object
>like a heat sink is more effective by moving the heated air away from the
>object.  Getting the heat away is the objective, and blowing on it is less
>effective than exhausting the heated air.
>
>73,
>Don W3FPR
>
> > -----Original Message-----
> >
> > I've made a cooling 'plenum' for my K2, using a very lo-profile cover
> > and a tiny muffin fan from a CPU cooler. It pulls cool air in from
> > outside across most of the heatsink fins and exhausts straight up. I
> > can supply illustrations and some info on the design if you, or
> > anyone else might be interested.
> >
> > Cheers,
> >
> > Tom   N0SS
> >
> >
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