After a month of perfect operation in FT8 mode, my sBitx v3 has stopped producing the output RF signal. I hoped it might be a software issue, like described here: .
Unfortunately, no correction in the software configuration restores the correct operation.
The status of my radio is as follows:
Reception works perfectly. The malfunction didn’t affect the receiver.
When I start transmitting in CW mode, the current consumption increases from 0.35A to 1.05A at DRIVE=100 or 0.84A at DRIVE=50. The peak-to-peak voltage at 14.068 MHz is ca. 11V for DRIVE=100 and 272 mV for DRIVE=50 (measured with 50 Ohm 40dB attenuator as a dummy load, and multiplied by 100)
The sBitx meter displays 0W and SWR=1.0
When working, the radio was used with the antenna matched via ATU-10-0A tuner with SWR up to 2.
The symptoms suggest that I have fried the transistors in the final stage due to too intensive usage in an FT8 mode.? Am I right?
Should I pair the replacement IRF510N transistors according to their threshold voltage when replacing them?
Is it possible to use IRF520 (with higher maximum ID) instead of IRF510?
