[Elecraft] Cool your KX3 (fredem)

[Don Wilhelm]

I also bought one of Fred's heatsinks for my KX3.
I tested the KX3 with continuous keydown at 10 watts for 10 minutes - 
shack ambient temperature of 22.5 degC (72 degF).
Without the heat sink, my KX3 throttled back to 5 watts after 4 minutes, 
30 seconds.  After the power reduction, the KX3 PA temperature began to 
cool since the stock heatsink is adequate for the 5 watt level in a 
normal shack temperature environment.  If there is direct sun on the KX3 
on a hot day, that is another situation (I did not test under those 
conditions).
With Fred's heatsink installed, the same test throttled power to 5 watts 
after 8 minutes 30 seconds, a significant improvement.

Fred provided me with a thermal pad for a test, and with that thermal 
pad, the time before power was reduced was 9 minutes 45 seconds.

So my conclusions are that the heat sink makes a big difference for 
continuous duty modes when operation above 5 watts is a goal.  The 
thermal pad made some improvement, but not terribly significant for most 
practical uses.

IMHO, the heatsink is an improvement to the KX3 for those who do 
continuous duty data modes and want to operate at power levels in excess 
of 5 watts.

There are at least 2 others who have posted that they are also offering 
add-on heat sinks for the KX3.  An archive search of the reflector posts 
will reveal those others.  I suspect that any added heatsink will 
improve the heat transfer to ambient air.

73,
Don W3FPR

On 5/2/2014 8:05 PM, Dave G. wrote:
> FWIW... I thought I'd mention this..
>
> I bought my KX3 heat sink from Fred Meier VE7FM a while ago.
> It is a very well machined precision product and fits beautifully,
> everything lined up perfectly - and it took me less than 10 minutes to
> install.
> I chose the micro bead blasted finish to increase the effective
> radiating area. (at least that's what I figured - I'm probably wrong!)
>
> It weighs about 8oz and I measured/calculated that it had a total
> dissipating area of just over 42 sq ins.
>
> The transaction was very easy and the delivery was very fast.
>
> I posted the list with my before and after results of temperatures
> reached for key-down continuous output transmissions at various power
> levels for a 5 minute duration at each power level into a dummy load.
>
> I had no temp induced shutdowns during my tests with that heat sink fitted..
> I've been using it for several months now with no problems.
>
>