[Elecraft] Some "Cool" heat sink info.

[Howard Hoyt]

Hi all,

Johnny, VR2XMC wrote:

>>It should not?be any rocket science, all you need is a piece of thick metal plate
>>to suck the heat from the PA transistors and with fins to facilitate air circulation.


You are right: a thick piece of metal will sink the heat from the PA 
transistors.  But how thick?  Too thin and there is little benefit. Too 
thick and the stored heat in the metal mass actually inhibits recovery 
time after a heating event.

How many fins?  How tall? How far apart?  And what combination of all of 
these gives the most benefit at a targeted small size?

You are right: it is not rocket science, but a dismissive attitude 
towards the importance of learning the interaction between the variables 
leads to some of the poorly-performing (not to mention ugly) designs I 
have seen hung off of several KX3s.  I also happen to agree with 
Elecraft's design criteria which is the same as just about all 
amateur-radio gear made:  100% power on CW and SSB, 50% power on digital 
modes.  To upgrade this to commercial broadcast equipment performance of 
100% duty cycle in all modes would greatly increase the price and size.  
If someone wants more power and xmit time in digital they can always buy 
a heatsink, and the cost of doing so is not added to the KX3 for 90% of 
the purchasers who do not need it.

More info on my website www.proaudioeng.com if you are interested,

Howie - WA4PSC