Hi Bob, There are several alternative RF designs for 100W transceiver applications which enable solid state RX/TX switching without the need for the old 100W PIN diode brute-force 50 ohm T/R switch approach, that takes a power supply almost as big as the one that is running the radio.
A high impedance receiver input can be coupled to the transceiver antenna port or filter bank, with a clamp circuit at the receiver front end for protection from overvoltage during transmit. The clamp circuit can be implemented in varoius ways. Also, power MOSFETs, or other types of FETs, could replace PIN diodes in standard 50 ohm switching applications for HF. ON-resistance of less than an ohm, and OFF-impedance of a few hundred or a thousand ohms at a few pF is all you need. The big advantage of FETs is that, unlike PIN diodes, they switch with very small current. Some of the FETs were mainly developed not for the HF transmitter industry, but for high power switching power supplies and motor control. Bonnie VR2/KQ6XA > Bob, KD7NM wrote: > high power PIN diodes ... for operation down to 1.5 MHz, > and can also handle a couple of hundred watts, don't > appear to be easy to find.
