Linear amp conversion to Mitsubishi finals

Nik VK4PLN has been doing further work  on upgrading the linear amp to Mitsubishi finals in his µBITx.  He says,

“So looking good so far. I am getting these output values: (RV1 adjusted(75%) for 20W on 80/40)
80m : 20W
40m : 20W
20m : 18W
15m : 17W
10m : 14W

“No feedback, but I have yet to test a QSO on 20/15/10m…

The configuration is:

RD16HHF1 finals,

  • BN42-202, but a 2:4 ratio winding giving 1:4 transformation.
  • 320pf on all 7 emitter resistors of the pre-amp chain
  • 330pf across the primary of the final’s winding.
  • 220 ohm feedback resistor.

The finals run cool at 20+w with 330pf Mica cap.    Nik is still considering changing out the driver and pre-driver transistors. 

Reference

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