[Elecraft] [K3] 150 watt "boots" for 160m

[Ignacy]

Those who believe in authority and that God punishes tinkerers, PLEASE SKIP
this message. 

2SC2782 is rated at 80W min each at 175 MHz so getting 150W from two on 1.8
MHz should be peanuts; the main reason why they are restricted to 110W in K3
is linearity (across bands) + component ratings. At higher power, the
efficiency can be higher and thus K3 may actually run cooler!

So how to get 150W out of K3?

1. ALC would not let it. It needs to be fooled, e.g., by changing a divider
in the SWR unit to indicate 100W when it is 150W. 

2. At 150W the output impedance would not be 50 Ohm; it would be 35-40 Ohm
with extra impedance added by LPF, which are designed for 50 Ohm.  You need
a manual tuner that you will tune for max power, not min SWR. If higher SWR
causes power fold up, the SWR circuit needs to fooled again. 

3. The radio would take more amps, say 30A, and the fuse may go out. If so,
change the fuse or reduce the power so that the fuse is not tripping.

Is it worth it, I am not sure. In contests, the extra power may make a real
difference.

Would Wayne and Eric approve? Never officially!
Would K3 be ruined? I doubt it.
Would I do it if I wanted to win a 160m contest in LP category and had no
other alternatives? Perhaps on CW but never on SSB due to high IMD.


Corresponding story
Many years ago a power supply for IC-735 broke and the spare one was for 5A
max. Tuned for min SWR the power was 5 W. Tuning for max power out generated
25W. 
Later, I tried the same trick with IC-7000. It was 5 W no matter what the
tuning because of strong power folding under high SWR. Not sure what K3
would do. But there is a possibility that one can get 10-20W more just by
tuning for max power out. 

Ignacy 

    

Julius Fazekas n2wn wrote:
> 
> Wondering if anyone has a suggestion of a solid state amp or "pushing" the
> K3 PA to obtain 150 watts out on 160m?
> 
> A kit or HB would be fine...
> 
> 73,
> Julius
> n2wn
> 

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