Re: Elecraft KPA500 vs Tokyo Hy-Power 1.1Kfx

Posted by David Christ on Aug 17, 2012; 11:31pm
URL: http://elecraft.85.s1.nabble.com/Elecraft-KPA500-vs-Tokyo-Hy-Power-1-1Kfx-tp7561226p7561230.html

I myself am not qualified to judge the designs, but a friend of mine
with decades of design experience at Rockwell Collins has been saying
from the first revealing of the KPA500 design that he would have used
4 devices not two.  If I understand his comments it relates to
current density and voltage.  With only two of these devices he says
you either have to run the voltage too high or have the current
density too high in order to get 500 watts.  He does agree that the
KPA500 is a nice amp but that he would have made different choices.
He was designing military/aircraft gear and had to allow a big safety
margin.

Hopefully a real engineer can tell me if this makes any sense.

David K0LUM

At 6:20 PM -0400 8/17/12, Robbins, James wrote:

>I am wondering if anyone has an explanation for why the Elecraft
>KPA500 amplifier (500 watts) employs 2 VRF2933 FETs (Microsemi) in
>the final PA where the THP uses 4 ST2933 FETs (STMicroelectronics) to
>generate very similar power levels.  The data sheets for each FET
>indicate that both brands are rated at 300-400 watts, support similar
>mismatches and run at similar voltage maximums.  They have very
>similar specs all together.
>
>Perhaps our amplifier gurus could weigh in here.  Much appreciated.
>
>73,
>Jim Robbins
>N1JR
>
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