Cooler KX™ is a line of painstakingly designed and meticulously crafted aftermarket heatsinks for the Elecraft® KX3 transceiver. It is currently available in two models, both of which are mechanically compatible with the Side KX End Plates and Side KX Cover accessories offered by AK6Q:
- The Cooler KX Lite™ which weighs 165 Grams (5.8 oz) – is sufficient for most work below 30 MHz and ideal for camping, SOTA, etc.
- The Cooler KX Plus™ which weighs 198 Grams (7.0 oz) – offers 20% more surface area, and may be preferable above 30 MHz.
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Based on what other KX3 owners are saying about this little radio, it is apparent that:
- In addition to being popular with SOTA enthusiasts and backpackers, this little radio is also seeing a lot of service as a main base station rig.
- Many users are upset about the radio’s tendency to overheat, at which point it automatically rollbacks its transmit power level.
- Some users are curious about frequency stability, and how temperature might affect the radio’s suitability for weak-signal digital modes like WSPR and JT65.
Wayne has chosen to limit the firmware reported PA temperature to 60° C – which probably correlates to an actual junction temperature closer to 85° C (185° F) – before taking protective counter measures. In contrast, the manufacturer’s datasheet specifies a maximum junction temperature of 150° C (302° F). This conservatism might be intended: to extend component operating life; or to account for the fact that the factory supplied heatsink can only dissipate a fraction of the power the PAs can produce; or to protect other nearby devices that are more temperature sensitive; or simply for the operator’s comfort and peace of mind. More than likely, he has chosen 60° C for a combination of these reasons, and others.
Many conditions contribute to this tendency for the KX3 PAs to reach Wayne’s self-imposed ceiling. Far more than one might realize without seeing them listed. They include:
- High SWR
- High TX output power level
- High duty cycle modes (Digital, FM, AM)
- Higher frequency bands (especially 6 m)
- Continuously transmitting – even in SSB – for longer than about 4.5 minutes
- Overall, spending more time transmitting than receiving
- High ambient temperature operating environments
- Inadequate ventilation
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Some effective homebrew solutions for this issue have been published, but none have been particularly portable, rugged, or attractive. Those “science experiments” inspired me to investigate the feasibility of offering an alternative – culminating in my painstakingly designed and meticulously crafted Cooler KX™ line of aftermarket KX3 heatsinks.
Elecraft is a registered trademark of Elecraft, Inc.
Cooler KX, Cooler KX Lite, and Cooler KX Plus
are trademarks of Friedhelm Meier, VE7FMN.
Copyright © 2014 by Friedhelm Meier, VE7FMN. All right reserved.