Based on the findings of an independent engineering evaluation, they rank first and second in terms of thermal performance (i.e. cooling benefit). Specifically, the Cooler KX Plus™ model placed first while the Cooler KX Lite™ tied for second place in this head-to-head test.
This subject is already addressed on my About webpage.
The answer depends on your cooling needs and your priorities regarding aesthetics versus your budget. The raw finish cools just as well as the painted finish, but costs about 26% less. Meanwhile, your cooling requirements depend on many factors, the primary ones being …
… so there is no one answer. Depending on your specific needs, it’s possible that a lesser heatsink will be sufficient, or that even mine won’t be, (without the use of a supplemental fan).
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As depicted in the plot below, the KX3’s cooling requirements (the two solid lines) vary widely – and in some rather unexpected ways – based not only on output power, but also on operating frequency. Output power being the separation between the input power (thin dashed) and waste heat (thick solid) curves. So the two “Hi” (red) curves correspond to roughly 10 Watts output, while the two “Lo” (blue) curves correspond to roughly 5 Watts.
Several operating guidelines can be inferred from this plot:
The above plot also tells us a lot about 6 meter performance. Most notably, that the PAs generate almost the identical amount of waste heat (20.4 W) running 4.6 Watts on 6 meters, as they do running 9.0 Watts on 15 meters (20.5 W). This observation prompted further 6 meter testing, the results of which are plotted below:
First let me restate what I think you are saying/asking … I think you’re saying that you don’t use high duty cycle modes (or perhaps you never transmit above 5 Watts) so you have never experienced a high temperature event. Nevertheless, you are thinking about upgrading your heatsink anyway, since doing so can extend your radio’s operating life.
As an aside, a general design principle used by the electronics industry is that a 10° C reduction in component (or device) operating temperature will result in a doubling of its operating life. Expanding on this statement, it follows that …
So the more a heatsink lowers the temperature of your KX3, the greater its benefit to you. And that benefit should be considered in addition to a heatsink’s cost. Conversely, the less a heatsink lowers the temperature, the less value it is to you!
Getting back to your question – given your circumstances I’m guessing you aren’t sure if you can justify upgrading to one of my premium Cooler KX™ brand heatsinks. Whereas you have a valid concern, an even greater concern (of mine) is that some laughably ineffective aftermarket heatsinks sell for ridiculously high prices, in comparison to what little thermal benefit they might provide.
So depending on which replacement product you choose, in the end you might have been better off had you just stuck with Elecraft’s original heatsink. I should add that in your situation, I recommend my Cooler KX Lite™ model without hesitation!
Depending on your operating frequency and output power level, even supplemental ventilation (i.e. a fan) might not be sufficient at temperatures much above 35° C (95° F) without additional mitigating actions such as transmitting less often or for shorter durations.
This question is already addressed quite thoroughly elsewhere, although not all in one place. Please refer to:
I suggest my Plus model for extended-duration high duty cycle transmissions running 10 Watts above 15 MHz. Depending on ambient temperature, SWR, TX duration, etc., my Lite model may or may not be sufficient for extended-duration high duty cycle transmissions running 10 Watts below 15 MHz. And although I suggest my Plus model above 30 MHz, you might find that my Lite model is perfectly adequate for your needs on 6 meters.
The general suggestions offered below are applicable to extended-duration high duty cycle transmissions …
I’m confident you’ll be pleased with the painted finish, but your choice should weigh your financial constraints against your form-versus-function priorities (i.e. how important are aesthetics). Hopefully the following discussion will answer all of your questions:
You might! Please review Tech Note #1 – PEM Nut Thread Damage.
No! I strongly discourage the use of thermal grease because …
Yes! Both Cooler KX™ models are compatible with both Side KX accessories, i.e. end plates and polycarbonate cover.
They are for mounting possible future accessories. I’m currently prototyping and evaluating two ideas; perhaps you have some ideas as well?