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That is a very interesting report that you present. Thanks for sharing your thoughts and experimental observation.
My experimental observation of the use of a high Q antenna was not as encouraging. I connected a homebrew link coupled base coil loaded antenna (where the loading coil is tuned by a parallel cap) to my SSTRAN and found that the audio was severely degraded. It sounded as if it was BW limited such as listening with cotton in my ears. I assumed that this was due to the narrow antenna BW and lowered the Q by placing a resistor (the one that SSTRAN suggests removing) back into the output circuit of the transmitter. The audio is now excellent.
There is a confounding effect which may have caused the unacceptable audio which I might have mistakenly attributed to the antenna Q. From an Electronics Workbench model of the circuit with a series RLC “antenna” I observed a badly distorted RF waveform as well as nonlinearity in the envelope of the modulated signal. This was confirmed when I observed the actual RF signal radiated from my antenna on a scope as I compared the “high Q” and “lowered Q” antenna performance. With the resistor in place, both the model and measurement yield a “text book” waveforrm. Since I was able to get excellent audio, I did not pursue this further.
What this suggests is that my unsatisfactory experience with the audio may not have been due to just the Q but may also have been due to presenting a load to the SSTRAN which it could not properly feed. Remember that the antenna I use is not the SSTRAN design and this problem could be the result of my deviating from the SSTRAN plans.