Hello Ken, In a french magazine (maybe Radio REF?) was published an article regarding a HF amp with two GU43B tetrodes. The measured output is over 2500W. If you need I may look to find that article and to scan it, let me know if you need this, will take some time for search and scan it. 73's from Bucharest, Traian, YO9FZS/p La6wea wrote: > Has anyone tryed to build an amplifier with Gu43b? 73 Ken