[Elecraft] [K2] Safely running 100% key-down modes

[Don Wilhelm]

Bruce,

The base K2 power is proportional to the power out of the KPA100 - so if 
the KPA100 is running at 20 watts, the base K2 is driving at about 2 watts.

You can run 100% duty cycle transmissions safely at 35 watts, and could 
probably push it to 50 watts if you provide auxiliary cooling for the 
KPA100 and the receive periods are long enough to allow the heatsink to 
cool.  You could increase the cooling by placing a muffin fan over the 
heat sink.

It is heat that will create problems - you can always use your fingers 
as an indicator.  If the surface of the heat sink is too hot to hold 
your fingers on it, it is likely too hot.  Don't forget that the base K2 
PA transistors are on the bottom rear.

73,
Don W3FPR

On 12/26/2013 12:06 PM, K1FFX wrote:
> I starting to use my K2/100 in two 100% key-down modes, JT-65 and PSK-31.
> What
> should I be keeping in mind in protecting the output stage for the K2 and
> for the KPA100?
>
> For JT-65, since it is a QRP mode, I'm running at about 5 watts, and
> transmissions are
> limited to about 45 seconds.  So, I'm hoping that K2's output transistors
> will not be stressed
> in this mode.
>
> But, how about PSK-31?  I'd like to run about 20 watts and each transmission
> could easily
> be 3 or so minutes.  I don't know at what output power the base K2 runs when
> the KPA100
> kicks in (i.e., at above 10 watts).  I assume that normally the KPA100 will
> be loafing at 20
> watts, but I'm not sure the impact of 100% key down on its output stage.
>
> I'd appreciate any guidance in keeping the K2/100 "safe" in these modes.
>
>