Mismatched loads on solid state PA tend to cause increased voltage peaks
or increased current peaks, probably not both compared to the matched
condition. These days the transistors are built to withstand these
deviations from normal. But they never improve DC to RF efficiency.
There is some room for SWR though that tolerance for SWR depends on the
particular design.
When I changed the rear axle gears on my small v-8 '98 F-150 for better
towing capacity it had the effect of raising the engine speed the same
amount as driving in 4th gear instead of 5th. I expected a gas mileage
decrease, but if I don't take too many kids at lights, the gas mileage
is the same.
Mismatch in the load will probably contribute distortion products,
including harmonics.
When my antenna fails, my SWR at the input of my manual tuner goes from
decent to very high.
In many radios the internal SWR shutdown protection shows up as super
high ALC with a little drive because the protection circuit protects by
asserting ALC.
73, Jerry, K0CQ
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Entire content copyright Dr. Gerald N. Johnson. Reproduction by
permission only.
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