I would be concerned about reducing voltage for SSB and TX IMD. The NXP 1K50H devices are only biased at 1 amp each which is a bit low for optimal IMD as it is. SSB IMD could be improved by increasing bias to 2 amps per device. Since the bias is only present during TX the waste heat increase would be negligible.
The FLex Power Genius XL uses same RF devices and they use 2 amps per device @ 52 volts on SSB. IMD at that spec on PG. L is very acceptable.
I am sure there is a reason I am overlooking for the Elecraft engineers to adjust bias to 1 amp per device.
Dave wo2x
Sent from my waxed string and tin cans.
> On Nov 13, 2020, at 10:28 AM, Roy <
[hidden email]> wrote:
>
> Yes, I read the same. Lowering the PA voltage might be a bit difficult...
>
> 73, Roy K6XK
>
>> On 11/13/2020 8:27 AM, Howard Sherer wrote:
>> Reading the display on the KPA 1500 at various RF output levels shows an
>> efficiency as follows on 40M into a dummyload:
>>
>>
>> 300W 23%
>> 500W 27%
>> 1000W 42%
>> 1300W 48%
>> 1500W 52%
>> 1600W 54%
>>
>> Have other owners seen results like this? Do you think a firmware and menu
>> item could be developed to increase the amps efficiency at lower power
>> levels by lowering the voltage to the PA?
>> ______________________________________________________________
>>
>
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