20 May 2016

Yaesu FT-891 update

Update: The Yaesu FT-891 is the smallest at lightest 100W HF transceiver ever built, at 155x52x218mm and 1.9Kg. Unfortunately the 2A current draw on standby makes it unsuited for truly portable operations.

Among other features worth mentioning would be the 3kHz wide roofing filter (yes, at the 69MHz IF) and the USB port that supports CAT, PTT keying and RTTY data.

04 May 2016

MRF1K50H - new 1500W LDMOS from NXP

LDMOS technology allowed huge improvements in RF power transistors in the recent years, bringing much better performance and efficiency at a lower price point than ever before. A pair of top-of-the-line MOSFETs of the late 80's such as the MRF157 are specified at 1.2KW with 45% effciency in AB class up to 50MHz and would set you back almost US$ 1000 even today. Compared to that, the new generation LDMOS offer more power than that at 70+% efficiency and 1/4 the cost, while they work up to 500MHz.

MRF1K50H is the name of the latest and greatest LDMOS RF part that comes out of the NXP laboratories. It is a small piece of electronics history in itself, being the most powerful transistor ever created in any technology, at any frequency (actually, it's a pair of transistors inside the MRF1K50H, but still applies). It has an output power of 1500W, works at 50V and up to 500MHz, typical effciency is 74% in AB class and the gain is 23.5dB @ 230MHz. There is also another version available called MRF1K50N that has marginally lower gain and efficiency, but compensates with a (30%) lower thermal resistance.