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I built a second amplifier yesterday, with a better matching design. And got a worse result!
I eventually figured out that there is a fair bit of parasitic capacitance in my layout. I removed the 12pF capacitor in the input matching network, replaced it with a 1pF and rewound inductors to add enough inductance. It now looks close-ish to the Qucs-S simulation. No such problem on the output network. Not sure yet what the extra capacitance is on the input. #HamRadio #AmateurRadio
The design had better matching at 10-20m meter bands, but as the current project is 2m band, I鈥檓 moving on.
Real performance is good. About 16 dB of gain at 145 MHz. I listened to airband traffic at 129 MHz and audio is good.
Still that weird resonance at 120Mhz. I鈥檓 going to get some different 1uH caps and see if it goes away on the next design.
It was a funny operation, matching the inductance. I had various hand wound inductors on the end of a foam tape and popped them in and out of the circuit while the NanoVNA was running.
After cutting down pads to try to remove capacitance, the working amp looks like this in the end. That lower copper clad is an attempt to add a better ground plane to a single sided PCB. Made little difference.
In case it鈥檚 not clear from the thread, the end result is great! Just took a fair bit of work.
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