[Elecraft] KPA500 faulting on high VSWR on power rise

[William Shanney]

I have found that a 4:1 balun is seldom the proper choice for a ladder 
line interface. I measure the impedance at the interface and then select 
the balun type (usually a 1:1). The biggest problem I've had is the 4:1 
transforming the impedance too low for the tuner. This can result in 
over stress on the components as the power is increased. If I don't have 
an easy to match ladder line interface I add or subtract line length 
until I get one.

73

Bill, W6QR