Looking for a HF amplifier for my FT-817 and some QRP home made rigs I have, I found this interesting kit from K5BCQ, a 160 to 6m amplifier with two RD16HHF1 transistors in A/B class. I ordered this kit from Kees, K5BCQ, a few weeks ago and these days the pack arrived in good condition. The kit price is quite reasonable, 50$ plus 7$ shipping to DX, and includes everything you need for the amp, except the LPFs and the enclosure, but for these two there are some hints on the schematic from the autor if you want to buy them elsewere. Also, I did not choose any heatsink option. My box height is not enough for those heatsinks that Kees offers.
The amplifier has a maximum input of 1W and there is also a place on the PCB for a “pi” attenuator with three resistors. In the pack supplied by K5BCQ there is a resistor set for a 3db attenuator, and if you don’t need any power reduction a jumper can be placed instead of the series resistor, leaving the other two unconnected.
The quality of the PCB board is exceptional. And it is only 76 x 66 mm, which can fit easily to some computer’s CPU heatsink-fan systems. I will not use this setup, as I said before, the height of my box is 70 mm, so the board plus heatsink and fan will be to much, and I don’t like to put them outside.
The kit is powered with a common 12V power supply. The RD16HHF1 MOSFET transistors are rated 16W at 12.5V in the HF band and they have much better linearity then IRF510. Also their price is not so big. For a pair you pay 10$ at www.kitsandparts.com.
All in one I think is a good investment. I read good reviews from other hams who build similar projects with RD16HHF1 transistors. At first I had in plan to build a project with IRF530, but after building about 50% of it, I abandonned that in favour of this. I already ordered a 170x150x70 metal box for this project and I will put inside also a LPF with Amidon toroids. These days I will begin mounting the components and hope to do some tests.