[Elecraft] KPA500 - Full Power Keydown

[Lyle Johnson]

The KPA500 RF deck and power supply can put out 500 watts for a very 
long time (definition of "very long time" is an exercise left for the 
reader).

If you are operating outdoors in direct sunlight in Saudi Arabia at 
mid-day in the summer, key down time is likely limited to a few 
minutes.  If the heat sink is covered in dust from a recent wind storm, 
it may only be several seconds.

If you are operating at the south pole in winter with a direct air duct 
to the outside to draw cooling air over the KPA500 heatisnk, you can 
probably operate key down for months -- and might need to to prevent the 
amplifier from being damaged by the extreme cold!

The point is that this is a thermal management problem.  If you keep the 
ambient air environment around the amplifier at a comfortable room 
temperature and ensure the fan and vents on the amplifier cabinet are 
not blocked, you can probably operate it at 500 watts as long as you 
have patience to hold the key down.  If the ambient air is not 
sufficient to cool the power transistors, perhaps due to temperature or 
limits on air flow, the amplifier will eventually shut down to protect 
itself.

Like many things in life, this is a system (ham shack station design 
including physical environment) issue, not a component (amplifier) issue.

73,

Lyle KK7P

> May be I would like to ask the question from another angle.  Can KPA500 be used for RTTY in a contest condition say at 500W?  If not, do we need to turn it down to 300W?