[Elecraft] Reducing K2 power below 1 watt (QRPp)

[Don Wilhelm]

Andy,

There *was* a non-Elecraft mod to accomplish that, but I am certain the 
links are no longer valid because the author has been SK for several 
years, and the mod documentation was on his website.

As I recall, that mod changed the resistors in the base K2 RF Output 
Detector.  That solution would not work in general now with a K2 with 
either the KAT2, the KPA100 or the KAT100 installed.

If I were to attempt a mod like that, I would want it to work even with 
the wattmeters in the KAT2 (or KPA100 or KAT100).  I would break the 
path on the Control Board between R12 and U6 pin 2 and insert a gain 
(non-inverting) op amp - hint remove R12 and add it back on the input of 
the op amp piggyback board.  I am going to guess that the op amp gain 
would be 10 or close to it, but some experimenting may be in order to 
make 1 watt fall at the 10 watt display and 0.1 watt fall at the 1 watt 
display.

You would have to switch the op-amp out of the circuit to tune the KAT2 
or KAT100, but other than that I can see no other operational difficulties.

A 10 dB attenuator with a power rating of at least 15 watts input would 
also do the job, but it would need to be switched out for receive 
somehow - a relay powered from an amp keying circuit should work to 
switch the attenuator in on TX and out for RX if you wanted to go the 
attenuator route.

For those who have the KPA100, you can always remove the power from the 
KPA100 and power only the base K2.  Doing that changes the power scale 
from 1 watt to 100 watts down to 0.1 watt to 15.2 watts (but you will 
find the power control will not be accurate much below 0.3 watts)

73,
Don W3FPR
  .
On 2/7/2013 10:22 AM, andyatd wrote:
> I've been searching for the best methods to modify a K2 for QRPp levels but
> the pages recommended seem to have expired accounts.
>
> Any suggestions would be very much appreciated.
>
> Thanks!
>
> Andy
> N3LCW
>
>
>
>
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