[Elecraft] KXPA100 duty cycle

[Jim Brown]

On 4/26/2013 5:09 AM, Gary Gregory wrote:
> I wonder why there is no cooling fan. I see a reasonable sized heatsink and
> of course power consumption is lower without the fan.
>
> Perhaps there is an opportunity to power an external fan from the APP
> output connector on the rear?
>
> Was this one application the designer had in mind?

One could always add an outboard fan, and I've done that when I thought 
a particular rig or amp might need it.  BUT -- Elecraft has been 
building power amps for a decade now, this is their third 100W amp, at 
least one key member of the design team is a serious contester and does 
RTTY contesting. They understand real world conditions, are very 
conservative in their designs, their amps have earned a reputation for 
being both robust and trouble-free. Back in my EE courses (nearly 50 
years ago now), I learned that it is entirely possible to achieve this 
with suitably rated output devices, a suitable heat sink and good 
protection circuitry.  I saw the demo piece at Visalia last week, and 
it's got a BIG heat sink.

Bottom line -- I trust their design.

BTW -- for those who may have missed it, the great functional difference 
between this 100W amp and the 100W amp in the K3 is that it is designed 
to be physically separated from the rig that drives it -- under a desk, 
under a car seat, in the trunk.

73, Jim K9YC