Discussion
I should have simulated this first! I spent an inordinate amount of time on VU2ESE Farhan's 5W JBOT amplifier and was unable to squeeze more than about 1.6W out of it. I took matters into my own hands, replaced some transistors with hotter models, rebiased, and squeezed 2.25W out. But it's SUPPOSED to be a 5W amplifier. Simulating it in Qucs-S without modification, I get 1.5W. My version: 2.2W. This design is just not capable of 5W on 12V. 🤦♂️ #HamRadio #AmateurRadio
@relistan Did you see a corresponding change in power when you altered the number of turns in the secondary of T3?
@relistan I can't see it doing more than a few watts with 2N2218s, regardless of the transformer ratios, though…
@synx508 Exactly. I used 2N2219As, which really are not capable of more than 0.5W each. And they are essentially equivalent to 2N2218s.
@relistan Certainly, when biased to operate linearly that's probably the very top end of what's possible. You'd be running into dissipation limits, too, if you had it biased for the lowest harmonic content. Maybe the designer had recalibrated their power meter to match their target power.
@synx508 I didn't mess with it in real life. In the simulator I cannot get it to output more power by adjusting the windings (well, changing the relative inductances)
@relistan sorry to see all your hard work with putting the board together not pan out
@fullywoolly thanks! Well, I learned stuff. I will replace it with a different design that gets at least 5-6W. No one can hear me on 20m with only 2W in the current band conditions.
@fullywoolly (this is SSB, not CW)
Install bonfire.cafe
Get the full app experience
