Galaxy DX-979 Aligning for best linearity.

Not all MOSFETS are created equal! That’s where being able to adjust the bias setting can achieve the best linearity for any particular mosfet or bipolar in the driver and final circuit. Sometimes the factory bias setting won’t achieve the best linearity and lowest IMD. You might have to experiment a bit.

With the factory bias setting, the best attenuation in this radio for 3rd Order IMD was -20b from the fundamental frequency. After experimenting with the bias setting, I was able to get -30db of attenuation and exceed 14 CFR Part 95 by 5db.

The beauty of an adjustable bias (found in 99% of cb and 10 meter radios) is that we negate the need for matched bipolar’s or Mosfet’s; keep that in mind and avoid the “snake oil salesman” who tell you different.