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Renewed attempt to hack together a workable PA #uBITX V6 #ubitx

 

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
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2n5109_Amp_20Bb_3dBpad_transformer_2InSeries.asc
2n5109_Amp_20Bb_3dBpad_transformer_2InSeries.asc

 

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Please post a linearity plot when you complete it. ?


Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

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Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

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Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:??bill@...

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On Sep 18, 2024, at 2:27?PM, AndyH <awhecker@...> wrote:

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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.
?
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.
?
73, Andy
?
<2n5109_Amp_20Bb_3dBpad_transformer_2InSeries.asc>
 

Will do.? The individual W8DIZ amps are very flat from 1-30 MHz. The spice model as I posted has a 0.5 dB drop from about 14 to 30 MHz for the pair. I'm cautiously optimistic, especially since this effort is based on advice from Allison.? I've finally learned enough to understand at least some of what she was trying to teach. Hihi
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73, Andy

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