[Elecraft] Question about K2 mod for optimizing it for 5W CW

[Don Wilhelm]

Alexey,

The R2 that is referred to by DK3RED is on the Front Panel - it is the 
power control pot.

There will be no change to any of the alignment procedures with the 
change in the T4 winding ratio.

Please put a sticker inside your K2 stating that the T4 winding ratio is 
intentionally changed to optimize efficiency at 5 watts.  I have worked 
on several K2s where this change was made, then forgotten about (or the 
K2 subsequently sold), and then the KSB2 and/or KPA100 was added, and 
the owner wondered why it did not operate correctly.

73,
Don W3FPR

Alexey Kats wrote:
> Sorry, I managed to press the wrong key and sent it before I finished it.
>
> Anyway... I know that older version of K2 manual refers to changing
> winding of T4 transformer to 2:2 (instead of original 2:3) in order to
> increase efficiency of CW performance on 5W or less. Is it still
> applicable to the current version of K2? I am not interested in SSB
> mode at all, so limiting max power to 5W is acceptable. I simply want
> to know whether the rest of tuning instructions will be the same if I
> change T4 winding according to those directions from rev C manual?
> (25-30% decrease in current drain is quite important when operating
> from batteries.) In any case, I am going to add 6.8k resistor to the
> R2 (of course it depends on the total resistance of R2 in the current
> kit) on control board according to DK3RED mod (which will limit max
> power to about 5W anyway), and I want to limit current consumption as
> well if I can.
>   
>