[Elecraft] K2: Does QRP-Mod (T4-winding) influence linearity of PA?

[Ron D' Eau Claire]

Thomas, DF7TV, asked:

> Planning to build the SSB-Option the rig will not be a
> CW-only one and I would rather accept less efficiency than
> less linearity.
>
> So does the 2:2 winding of T4 reduce linearity?
> Will the bias point of the PA be changed?
> (Could someone please explain me how efficiency is
> improved by this mod?)


According to the Elecraft manual, this mod does change the operating point
of the K2 finals.

It runs closer to Class A with the transformer wound as directed for 10 watt
operation. This mod moves the operating point toward Class C, thereby
reducing the current drain required but also reducing the linearity.

As I recall from a number of such questions asked here in the past, Elecraft
does NOT recommend using the K2 in SSB if this mod is installed. It should
be operated only in CW mode.

Also, the maximum power output the rig can provide is reduced.

The only purpose for this mod is to reduce the current drain at 5 watts
somewhat for those who intend to keep the power output at 5 watts or less
and work only CW.

Ron AC7AC
K2 # 1289