Re: KPA-1500 on digital modes

Posted by John Simmons on Aug 29, 2019; 7:04pm
URL: http://elecraft.85.s1.nabble.com/KPA-1500-on-digital-modes-tp7654828p7654851.html

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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