[Elecraft] SWR - does it matter?

[Andy Durbin]

As a counter to those who are asserting that SWR 1.5:1 is a good enough match for an antenna system I offer measured data for the KPA500.

At 14.005 MHz my KPA500, when connected to a 1.44:1 SWR load (R37, X9), had a PA dissipation of over 500 watts when producing 400 watts RF output.   When the load was changed to 1.30:1 (R39, X3) the PA dissipation was about 410 watts.  When the load was changed to SWR 1.07:1 (R49, X3) the PA dissipation was reduced to under 400 watts.   (The plots are far more informative than a text description but I can't post them here).

If you don't mind your KPA500 running hot, and are prepared to accept it shutting down with PA DISS fault, then 1.5:1 SWR may be good enough for you.   I'd rather know the complex impedance of the antenna system load and avoid loads that result in high PA dissipation.

73,
Andy, k3wyc