I'm doing some experiments with a home-brew transmitter project. I have everything working, but the weak link is the driver stage before the final transistor. The PA board is this: http://qrp-labs.com/pa I did all of the recommended modifications, including replacing the switching FET with a real RD15HVF1 RF transistor, which is supposed to extend the "flat" gain output range of the PA board into the low VHF range. The exciter is the sinusoidal output of an AD9850 DDS. This is very low power, so I'm using an intermediate driver stage amplifier, consisting of a single BS170, very similar to the driver circuit used by the QRP Labs U3S transmitter project. This amplifies the DDS output enough to drive the 5W PA, at least on the low bands. This arrangement works for frequencies up to about 30m, where the driver transistor gain is starting to roll-off. The BS170 can drive the 5W PA board on 80m and 40m to about 4.5W, but the output is down to 1W by the time I get to 10m. Obviously, the BS170 wasn't meant for HF RF work, so I'm looking for a transistor that I could use to replace it. The circuit needs a part with reasonably flat gain across the HF bands. I'm sure I can dig around on Mouser and find something that looks good on paper, but I wonder if any of you have a favorite intermediate HF power FET that you prefer for this kind of application?