Well, it was not easy to make the right decision: What transistor is the very best on the market? I did some research and came out with the MRF154/7 family even when they appeared to be very expensive. There are some competitors: The ARF1500, ARF1501 and ARF1502 are much cheaper and provide even more power! Also higher voltages should provide better IMD - so how about using them instead?
The ARF-family is designed for just 40MHz - so no chance for 6m-operation. (Bad for my IC-7700...)
Gain is good (17dB), but much below the MRF157.
The ARFs are designed for class "C" operation and NOT for SSB - this was the most important difference! These HOGs are specified for 900Wout but "only" 1500W total dissipation - a clear sign for an optimization for FM-Class "C" operation with high efficiency. (> 75%!)
The specs tell about Medical applications @ 27,12 MHz - a typical RF Generator MOS FET application.
Measurements in linear designs (with adequate BIAS) came out with just 25dB IM3 @ 80% load...
Summary: Big signals with just 25dB (IM3) and no 6m. When paralleling 2 push-pull-amplifiers you will need about 200W! of drive-power ...
The MRF 154, MRF157:
Operation up to 100/80 MHz (6m is included), Gain is up to 21dB, designed for Linear High Power RF Applications, mainly in military applications. Power dissipation is only 10% lower than the ARFs. IM3 is specified and can easily reach 35dB+. Using 2 push pulls need just 20W drive - the exciter can provide a much cleaner signals!
For your convinience you can download the most important transistor-information here:
BLW 95: www.duessler.de/BLW95.pdf (Bipolar Transistor, 160Wout - Used in KSG-modules and KSG 1300)
MRF 150: www.duessler.de/MRF150.pdf (Bandwidth up to 150 MHz, only 150Wout - Used in EB-104 projects)
MRF 154: www.duessler.de/MRF154.pdf (Bandwidth up to 100 MHz, Gain is 17dB, 600Wout)
MRF 157: www.duessler.de/MRF157.pdf (Bandwidth up to 80 MHz, Gain is 21 dB, 600Wout)
ARF1500: www.duessler.de/ARF1500.pdf (ARFs not used, see text above - Gain is 17dB in Class "C", 900Wout)
Therefore: Power is never an issue - "crystal clean" power is the goal! Achieving this along with high gain and high bandwidth is a clear advantage and finally made the desision for the big MRFs.