The EB 104 construction started with a lot of preparation - copper coolers, aluminium heat sink, drillings and the construction according Helge Granberg's advises. Unfortunately the completed amplifier started oscillating and was not easy to adjust in terms of stable bias values. Also the board showed a slightly different diagram than on paper.

In short - it was very time consuming and also a lot of work to complete this amplifier. A list of around 30 Mods ! was the result of all this R&D work. Also its no secret that I lost 8 MRF150's over 2 weeks while working on them and making them safe for future operation. The worst thing is the circuit board itself which doesn't take much care about correct RF grounds, RF flow to sensitive components or correct capacitor locations. The EB 104 has also a mini RF choke which is just there for feeding the MOS FETs with 48V and for creating a feedback loop for better gain on higher frequencies. This component is risky - I did not solder it the wrong way, but doing this kills all 4 transistors right away! But even doing it right will send more RF back to the FET-Gates than both resistors can handle - in other words the resistors start burning over time.

The bias couldn't be adjusted as described at all - the installed mini-trimmers showed an adjustment window of one or two degrees for correct values - very, very unstable.... All this had to be modified and optimized.

Lots of small things summed up into a more than complicated design. So, if you decide to go for the EB 104 it will still be a bit risky but it is possible to get this up and running at the end.

Finally the EB 104 delivered easily 700W into my dummy-load up to highest frequencies but also into complex loads under test. The next step will be completing the second one fully identically to #1 and combine them to 1200Wout. Once this is done the amplifier will be tested at all loads and circumstances.

And "yes" - I would do it again. What is HAM-Radio nowadays? Correct, making it all work and learn more about RF designs - especially for RF engineers and on complicated designs... It was both fun and work - the right thing for 2 weeks rainy vacation over Christmas - once again "special thanks" to my family!

 

Here is all the pre-work prior any problems:                                            Starting EB104

Here are some pictures with several mods and under test:                        Mods & More

 

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