[Elecraft] KPA1500 Solution to the efficiency problem?

[Roger D Johnson]

I think I've discovered a fly in my ointment! The efficiency
that the amp displays is based on it's determination of the
output power. If the amp is looking into a higher Z load,
the indicated power is greater than normal resulting in a
higher efficiency reading.

Oh well, back to the drawing board!

73, Roger


On 8/31/2019 9:32 AM, Roger D Johnson wrote:
> It occurred to me that the KPA1500's built in tuner might be of
> some help.
> 
> Here's my reasoning. If we decrease the drive power to lessen
> the output power but keep the same voltage, the amplifier wants
> to see a higher load impedance.
> 
> Here are the results of some quick tests:
> 
> Base line is the amp set for 1000 watts output and eff is 44%
> 
> I the set the tuner so the amp "sees" a load of 60 Ohms (actually)
> 58 Ohms with the values of L and C available. Eff went up to 53%!
> 
> I then set the tuner to present a 70 Ohm load (actually 68 Ohms).
> Eff went up to 59%!
> 
> This was into a dummy load. I realize that, if you're using the tuner
> to match an antenna, this could be very complicated.
> 
> If Elecraft could figure some way to give us a choice of voltages
> for differing power levels, this problem would go away.
> 
> 73, Roger
> 
> 
> 
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