I have been using my Ten Tec enhancement box for a bit less than a year. CW and FT8/FT4 work just fine. But I have had a lot of complaints about RF on the voice signal. Some people even though I was being malicious. That was not going to work.
I tried a variety of RF mitigation techniques and none of them worked.
Until...I made two observations. One was that all power returns in the Ten Tec were routed through the chassis. The other was that all the voice input paths were isolated from the chassis using an insulator (maybe some sort of phenolic material). That told me everything I needed to know. I had made a mistake not isolating the microphone path from the enhancement box chassis. Even after isolating the microphone path, some of the RFI problem remained. The most likely path was the sound blaster dongle.
I also encountered a second problem. The Mean Well 350 watts, 12 volts power supply has a maximum output of 12.6 volts. The Astron power supply providers about 14.5 volts. Since the power output of a Class AB amplifier changes by the square of the supply voltage, one can expect a reduction of about 30% in the power output. That is exactly what I observed. 70 watts max output rather than 100 watts.
The solution involved two steps:
- Replace the metal box with an ABS box (at least for now with its own power supply)
- Go back to the Astron power supply.
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