Most radios won’t run on 20V or higher. At 15V or lower, USB PD is limited to 3A.

If you wanted to get 100 watts, you would need a buck converter to step 20V down to 13.8V. Now you have two switch mode power supplies producing RFI.

How much RFI do those power banks spew out?

USB PD only goes up to 3A at 15V. That’s not enough current to run a mobile radio.
A small LiFePO4 battery is a much better choice as it will supply a stable 12.8V without any switch mode supplies.

SDR++ seems to work the best with my RSP1A, I still have to use a closed source driver that hasn’t been updated since Dec 2019. At least the driver works fairly well, but sometimes it locks up and the sdrplay service has to be restarted.

The Android driver, on the other hand, is completely broken. It usually crashes within 5 minutes and it only supports up to 2msps. They haven’t updated it since Feb 2019.

It works, but it’s closed source and pretty basic. I just wish they would release an open source driver.

You could try some Motorola DTR or DRL radios if you want something license free and not super expensive. Motorola claims they cover 300,000 sq ft indoors. They put out 1W on 915MHz, they use frequency hopping spread spectrum, and they have digital audio.

For higher voltages, you could build a Pierce oscillator from discrete components instead of using a hex inverter.