[Elecraft] KAT3 L10 burned [likely cause, and what to do]

[Wayne Burdick]

Giulio,

The load impedance was probably extremely low, and at full power on  
this particular band, the power-handling capacity of the 8.2-MHz IF  
trap was exceeded. It's possible that the trap was mistuned (too close  
to 40 or 30 m). Note that L10's winding is adjusted at the factory and  
should not be moved.

If you contact support, replacement components (L10 and the associated  
capacitor) will be sent out immediately. Support can also explain how  
to adjust the trap to 8.2 MHz (or the parts may be pre-calibrated as a  
pair -- they'll let you know).

As a precaution, I will also be modifying the ATU matching algorithm  
so that it catches this case, preventing excessive reflected power  
that could damage the trap. I'm guessing that the load SWR was in  
excess of 10:1 or 15:1 at the time -- the KAT3 has a *very* wide  
matching range, and probably presented something close to 1:1 to the  
transmitter.

73,
Wayne
N6KR