[Elecraft] KPA500 thermal clicks

[ANDY DURBIN]

The clicking of my KPA500 is almost intolerable and I'd like to know if what I'm experiencing is typical.


In an FT8 TX/RX cycle  with output power 126 W my KPA500 clicks 7-8 times during 15 second transmit and 7-8 times during 15 second receive.  In these TX/RX cycles my logger shows the finals temperature swings between 57 deg C and 63 deg C.   During  this test the KPA500 was seeing an SWR of 1.02:1  and calculated PA dissipation was 307 W.


I don't think this temperature swing is likely to cause the heat sink to expand and contract significantly.  The thermal mass of the heat sink is quite large and the heating and cooling periods are short.    The first click happens almost as soon as the KPA500 is keyed.


I think it is possible that the clicks are caused by expansion and contraction  of the finals at their mounting points.   Is that likely and, if so, why would it be considered normal?


73,

Andy k3wyc