Solar Powered 80m cw QRPp Tx

The Tx which was designed by Jonny Apell, SM7UCZ gives about 20mW.

Solar Powered 80m cw QRPp Tx

A plot from my Spectrum Analyser showing the first few harmonics from the transmitter when it is correctly terminated with a 50R load. As can be seen, the 2nd harmonic is only 22dB down from the primary frequency, this is not really good enough despite the low output power of the transmitter (The peak at the left edge of the display is the zero reference marker).

I've since talked with Jonny by email and he said Maybe the output impedance and filter don't match? Impedance is about V2/(output power × 2)
So 3.6V × 3.6V / (0.02 × 2) = 324 ohms !! We need a transformer there!!

Spectrum plot with Tx terminated with 50R

The same plot with the Tx unterminated. The 2nd harmonic only 18dB down.

Spectrum plot with Tx unterminated

A wider plot of the correctly terminated Tx, I don't know why the 5th harmonic is lower than expected.

Wide Spectrum plot with Tx terminated

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