I have three low-band QDXs (and a high-band one on the way), built for 12V operation, and I did manage to burn up the PA? on one (literally, with scorched FETs, driver IC, and PCB) when running at 12.5V into a poor antenna.? This was FST4W-120 (like WSPR).? The QDX ran fine for a few weeks, but then went kablooey.? My fault.??
Since then I have been running the QDXs from a 9V supply, and into a reasonably good load.? Zero problems, and these are running at close to a 50% duty-cycle, with two-minute transmit sequences.
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Paul Elliott - WB6CXC
