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The 1.5kW transistors

Semiconductor manufacturer NXP announced a couple of LDMOS power MOSFET transistors, the ceramic-cased MRF1K50H and a plastic cased equivalent earlier this summer and they are now starting to become available. Initial information was sketchy but more detail is emerging. Both transistors are rated to work from 1.8 - 500 MHz at an unbelievable power level of 1500W, even for 24/7 FM radio application. Heatsinks and cooling will be a major challenge that may limit the amount of power that is practically achievable of course.

NXP MRF1K50H

Both transistors have a gain of around 23.5 dB of gain, so should be capable of providing over 1kW from a drive of about 5W. NXP are also claiming they will handle a VSWR of 65:1, although the test conditions for that measurement appear to be for radar applications where the transmissions are short pulses.

There is not much information on HF radio applications but they do quote a CW power level of 1550W and 25.9 dB gain at 27 MHz.

product datasheet is available from NXP's Freescale website which contains reference designs including board layouts for broadcast applications. Perhaps unsurprisingly the data sheet does not contain advice on heatsinks.