[Elecraft] [Elecraft-K3] K3S to be discontinued

[David Gilbert]

I agree completely with all of that, but with the discontinuance of the 
K3s it seems that Elecraft doesn't really consider the K4 to be strictly 
a base station rig.  Their continued insistence upon everything being 12 
volt capable is a bit of a puzzlement for me.

73,
Dave   AB7E


On 11/4/2019 1:37 PM, Joe Subich, W4TV wrote:
>
>
> The issue is that 12V transistors are simply not capable of providing
> the "clean" voltage swings necessary to generate 100 - 120W peak power.
>
> A typical transistor/FET has a series output impedance of around 1 - 1.5
> Ohms.  Thus if the peak current is ~10A per device, the transistor is
> operating from cut-off to saturated - with the unavoidable distortion
> (clipping/saturation) at each end of that range.
>
> Simply put, insistence on more than about 60 W PEP from a pair of 12V
> devices is *asking for IMD* and "active predistortion" only masks that
> issue with a significant cost in complexity and DSP hardware.
>
> Equipment designers should give up on 12V devices for "base station"
> radios and go to 48V devices - even at 200 W PEP output levels. The
> designers should stick to 60 W output for 12V devices.  That level is
> more than enough to drive an amplifier in the  KPA-500 class to rated
> output and close (if not sufficient) for even a KPA-1500 and can be
> improved, if necessary, with much less complex precorrection systems.
>
> Redesigned with bias levels and transformers optimized for the lower
> power levels, perhaps with increased negative feedback, the K3/K3S
> could exhibit *much* - at least 10 dB - better IMD at 50 - 60 W PEP
> output (although efficiency would probably suffer for those who just
> absolutely need to run the rig from a 12V battery pack on a picnic
> table).
>
> 73,
>
>    ... Joe, W4TV