Central Electronics 600L

[sndtubes]

I have a Nick Tusa restored 600L.  I am currently driving it with a 200V.  On 80 meters when I run at 500 watts input I get about 300 watts out.  Seems reasonable.  But 10 and 15 are a different story.  With 500 watts input I am only seeing about 100 watts out.  This seems very inefficient.   Is this a byproduct of the broadband couplers or do I have something amiss?

[WQ9E]

Are you measuring into a dummy load with a known good meter?  The broadband coupler design in the 600L requires the load to be well matched and any significant deviation will greatly reduce output, the 25 to 100 ohm output capability is for pure resistive loads and complex impedances still in this range may not be matched well.

What you are seeing is not normal on 15 and 10, output will be down slightly due to lower efficiency on 15 and 10 but not anywhere close to what you are seeing.