And pretty typical for amateur transmitters. Rarely does one see that 75% or 80% efficiency as listed in the tube data sheets. The given power output figure is the output at the plate of the tube, and doesn't take into account the losses in the tank circuit, antenna tuner (if used) and feedline. Most amateurs would be disappointed if they were to take an accurate reading of their output power as measured at the feed point to the radiating elements of the antenna.
Generally speaking, I've got to agree. I've checked a number of commercial amateur transmitters using a Bird wattmeter and a 50 ohm dummy load. The worst offenders are the novice transmitters that double in the final on 10 meters. Their efficiency at that frequency are typically about 30%. The 100 watt class rigs do better with efficiencies in the low 60% on 80 meters dropping to about 50% on 10 meters. Two standouts are the Viking 500 and the KW-1. Both had efficiencies of close to 75% on 80 meters and better than 60% on 10 meters.
Darrell
