Sorry...I broke the thread.
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I've decided not to use the K9HZ amp due to its size, and to stick with the QRP-Labs 10 W board with it's much smaller heatsink requirement.? I'm looking for a fairly flat 10 W output from 80 to 10 that will easily fit into the existing uBITX case.
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I think I'll use two stages of slightly modified W8DIZ 2N5109/2SC5551A amps to replace the Q90 and Q911/912 stages.? The attached LTspice model is my current best guess.? The total gain is about 34 dB, with an output of about 1.6-1.65 V peak, slightly above the 1.58 V peak for a 14 dBm input to the QRP-Labs amp.? There appeared to be some gain interactions when adding the second stage - it took a couple of rounds of tweaking to get the gain back in line.? The R14/15/16 pad might need to move up from 3 dB to 4.? We'll see how well hardware mimics spice.
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73, Andy
