Re: FT-857D Digital Operation
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Doug,
That duty cycle issue is a sign of an impedance (not SWR) mismatch at the antenna system, combined with higher power.?
It's not that FT8 presents any problem, unless there's something wrong with the antenna that isn't known about, and too-high power (>50 watts).
I had to replace the MOSFET finals in my 857 as well - and that, after years of successful operation, turned out to be why.
While I was fixing the rig, I checked my antenna system with an actual VNA, not just an SWR bridge or handheld antenna analyzer.
I found that what was going on was that the automatic antenna tuner was finding a low SWR point, but NOT at 50 ohms. It was presenting about 21 ohms of impedance at 1.2:1 to the radio. Best it could do until I made some positioning changes to the Windom and gave up on the G5RV. Those changes made it possible for the tuner to present both low SWR _and_ a lower impedance to the radio.
I never run more than 25-30? watts on FT-8, or anything else for that matter. Remember the rule about S units vs watts. You're not going to make your signal vastly better just by running your radio at 70 watts vs 40.
And your finals will be able to handle a wider variety of less than perfect conditions than they will if you nearly max out power.?
73, Tim KA4LFP? ------
Our civilization could well die of indifference within it, each group
deliberately indifferent to its own failings and too preoccupied with other groups failings, before succumbing to external attack.
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Real Radios Glow in the Dark
Morse code - The original digital mode!
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