My most recent post about this ion source itself was here:
http://www.fusor.net/board/view.php?bn=fusor_construction&key=1232950251
I just added a new amplifier stage to drive the AM-6155. I had been driving it with an old Mini-Circuits ZHL-2, which only managed about a watt output, max. This got me a maximum output of ~75 W from the AM-6155, which was running in Class-A, linear mode in order to enable that kind of output. The new stage is a broadband, linear amplifier good for about 10 watts out. It uses a Polyfet SQ202, a push-pull MOSFET amp, in the test circuit described in the manufacturer's application note here:
http://www.polyfet.com/tbplt/tb165.pdf
I did not make the circuit board itself--that was made by Jim Potter, who builds the RF hardware for the accelerator company I work for. These amps are a standard part of the low-level signal train for what ultimately is a ~hundred kilowatt power plant.
The amp I built, shown in the photo, had over 15 dB small-signal gain all the way from 30-500 MHz when I checked it on the network analyzer at work. At 200 MHz, it was 15.3 dB. When I got home, I tried running the AM-6155 with it. Even with the amp in "tune" mode, with the grid bias probably putting it in Class C, I can get close to 200 W out with ~6 W out of the SQ202 driver. Flipping the bias switch back to the "operate" setting for a second appears to get about 0.5 kW, at a great expense in terms of efficiency. I know some in the ham radio community like to push this amplifier, but I will be running it CW and don't need all that sauce. I'm happy with 200 W and the improved efficiency of a less linear bias point.
That's all for tonight!
-Carl
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2008-01-09 02:15 RF for new ion source 
(Carl Willis) [Latest: 2009-19-10 18:27]
2009-17-02 00:06 Re: RF for new ion source (NEW DRIVER AMP) 
(Carl Willis)