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I have a roughly ten of these MPSA18 darlingtons coming in the mail to play with and was wondering if they would increase the drive level in the ubitx?

I mean, I can always just solder them in and see what may happen, but I was curious if anyone else had rebuilt the driver stage and played around with it?
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N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist

my favorite to92 npn gain guy. bes
ide the xx390x twins the best transistor you can buy. tayda sells .12 each hfe ~400-500

The hfe on these is typically 1150. Max is 1500, min is 500. I was curious as to if the higher gain might help with the drive on 30 meters and up.

https://www.jameco.com/Jameco/Products/ProdDS/210681.pdf
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N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist

Also have some MPSA13 coming in, those are the darlington, not the MPSA18, sorry about the confusion. Part number is pretty well the same except one number.?

The 13 is what I meant to ask about using in the drive circuit and realized that after checking the data sheets again this morning.



That part has a really high hfe, which is what made me curious. On the range of 5000.
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N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist

Just going to bump one last time, anyone have any ideas on rebuilding the driver stage?
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N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist

IF your using darlington devices you need to change the bias or the result will be very poor and distorted.
Also the FT is 125mhz, by 14mhz your running out of gain (beta).? HFE is a DC gain and done not hold
to higher RF.? MPSA-13 is a bad choice.? ?The MPSA-18 is no better.

For Q90 and Q911/912 I'd use 2n2369 a device with a 600mhz FT.? ?Its available as leaded to18 metal or
SMT.

For the driver I'd use 2n2222A (not the plastic PN2222 which is lower performance) in the to18 can or
the MMBT2222 series if SMT is needed.

The key parameter is a FT of not less than 300mhz and higher is better.? HFE, no so much as its
not a predictor of gain at high RF.

Allison