Posted by Bob McGraw - K4TAX on Aug 29, 2019; 7:11pm URL: http://elecraft.85.s1.nabble.com/KPA-1500-on-digital-modes-tp7654828p7654853.html
My KPA500 runs from a low of 35% to a high of 55% depending on power.
Lower power is least efficient. Thus I always run close or at maximum
rated power. Also the load impedance will affect efficiency.
73
Bob, K4TAX
On 8/29/2019 2:04 PM, John Simmons wrote:
> No one has mentioned amplifier efficiency at differing power levels.
>
> -John NI0K
>
> Andy Durbin wrote:
>> "They bias the LDMOS devices at 1 amp each. That is minimal in
>> overall heat when you are pulling over 40 amps at high power."
>>
>> You beat me to it. My KPA500, keyed but with no RF input, showed
>> 0.5 A at 76.7 V. That's only 38 W which is a small part of the 400 W
>> plus PA dissipation seen in some operating conditions.
>>
>> All my measurements of PA dissipation take PA DC input and subtract
>> RF output so my data include dissipation in the LPF. It would be
>> interesting to separate the dissipation in the finals from the
>> dissipation in the LPF but I don't know how to do that without
>> modifying the amplifier.
>>
>> 73,
>> Andy, k3wyc
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