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

[Bill Coleman]

On Dec 26, 2013, at 12:06 PM, K1FFX <bruce.rosen at rcn.com> 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?

I’ve used the K2/100 in RTTY and PSK31, even for contests. As designed, I don’t believe that Elecraft recommends running more than about 25 watts out in these 100% duty cycle modes. You can run 50-100 watts for short periods, but there really isn’t enough cooling.

I modified my K2/100 by adding a small fan, mounted on rubber feet that sits on top of the heat sink, right where the power transistors are. It blows air down into the heat sink continuously. I have no problem running 50 watts RTTY in this configuration for hours and hours, and could probably run 100 watts with a slightly larger fan. 

> 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.

If you run less than 11 watts, the KPA100 deactivates, so you are just running the base K2 only. You’d be better off running 11-25 watts, and using the KPA100, than stressing the K2 output transistors.

> 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.

Should work great.


Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at mac.com
Quote: "Boot, you transistorized tormentor! Boot!"
         -- Archibald Asparagus, VeggieTales

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
           -- Wilbur Wright, 1901