The value of SWR doesn't really inform us about the load impedance, line
current or line voltage conditions existing.
In the case of a 1.5:1 SWR, the load Z is 75 ohms, with a power of 500
watts the line current is 2.58 amps with a voltage of 193.6 volts.
At the same time a 1.5:1 SWR, the load Z is 33.3 ohms, at 500 watts the
line current is 3.87 amps and with a voltage of 129 volts.
Both 75 ohms and 33.3 ohms represent a 1.5:1 SWR with reference to a 50
ohm source.
The points being related to the circuit designs, how much current or how
much voltage exceeds the component ratings? Hence we see
manufacturers specifying maximum SWR values. Added to the above is
the Xl and Xc values plus R for a complex impedance.
73
Bob, K4TAX
On 9/2/2018 2:21 PM, ANDY DURBIN wrote:
"The Elecraft KPA500 amplifier also works efficiently into a load SWR of 1.5:1"
Any such claim is at best misleading. There may be some 1.5:1 loads that that
the KPA500 will be happy with but there are other 1.5:1 loads that it will
object to, to the point of giving multiple PA DISS faults. 1.5:1 SWR does not
define the load characteristics. A 1.5:1 load could be pure R or it could be
a complex impedance. The efficiency, PA dissipation, and risk of fault trip
are not defined by the SWR.
73,
Andy k3wyc
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