I've checked this extremly simple concept for spurious emissions and whether they're compliant with the current regulations ...
Harmonics
I ran a spectrum scan on my Frog to check for harmonics on the output signal.
The measurement was done using an Siglent SSA3021X and the FA power attenuator.
| Peak | Frequency | Comment | ||
| 1 | 7.057 | Main carrier. Abt. 25dBm what is 300mW | ||
| 2 | 14.058 | 1st harmonic. Abt. 19.dBc below carrier. Far too less, I must check this. | ||
| 3 | 21.060 | 2nd harmonic. Abt. 40dBc below carrier. This corresponds to the regulatory authorities. But not good. | ||
| 4 | 28.140 | 3rd harmonic. Abt. 48dBc below carrier. This is fine. |