funny you should mention that. here's a MOSFET amp. the MOSFET is 10-15 dollars US (compared to about 50-100 dollars for the MRF-232), and the part is made by Mitsubishi. the part number of the MOSFET is RD15HVF1, and according to the data sheet is impervious to high SWR. the bias control (U1 in the schematic) sets the operating point of the MOSFET. depending where you set it on it's conduction curve, you'll get between 2 and 15 watts out. the transistor must have a heat sink, and this FET has a different pinout than most, GSD instead of GDS. this is so you can mount it on a heat sink without the capacitance effects that the heat sink tab would normally present. it also provides isolation of the parasitic capacitances between G and D. if you try this with a regular TO-220 type MOSFET, the drain tab will act like a big capacitor and kill most of the output signal.