The power output of a solid state final drops quite a bit when the
supply drops from 13.8 to 12 volts. Typically Vsat on the PA transistor
is a couple volts, so the swing is limited to supply - 2 volts. The
output load line is fixed by the output network so power output is
proportional to the square of the voltage swing. 13.8 -2 is 11.8 volts
peak swing. 12-2 is 10 volts. The ratio of their squares shows that a PA
can only put out 71.8% at 12 volts than it put out at 13.8 volts. At 10
volts that same PA can only put out 46% of the power it did at 13.8
volts.
Some Scouts seem to have problems with voltage drop in the leads and
power connector to lead to voltage regulation problems when the voltage
drops below the required input voltage for regulation. The best of
voltage regulators require less than half a volt drop to maintain
regulation, while the more common 7800 series require more like 2.5
volts drop for regulation.
The voltage regulator on the control board in the Corsair II puts out
8.2 volts. Looks like the absolute minimum supply has to be more than 3
silicon junctions higher, probably more so at least 10 volts to remain
regulated. The manual specifies power required 12 - 14 volts. 850 ma
receive 18.5 amps transmit.
Now I have a question. How is it possible to communicate with any Tentec
radio without antenna and feed line?
73, Jerry, K0CQ
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