Home |
Search |
Today's Posts |
#10
|
|||
|
|||
Efficiency and maximum power transfer
Richard Fry wrote:
"Walter Maxwell" wrote What seems to be overlooked here is that the source resistance at the output terminals of the pi-nework in Class B and C amplifiers is non-dissipative, which is the reason they can be loaded for delivering all available power for a given grid drive, and still have efficiencies greater than 50 percent. One of the myths circulated for years, and still prevelant, is that the reason for Class B and C amps to have efficiencies greater than 50 percent is that the load resistance must be greater than the source resistance. Tain't so. ____________ Walt - what is your thinking on the point that untuned, solid-state amplifiers also can have PA DC-to-RF power conversion efficiencies of 70% or more at the device level? In fact the solid-state, analog FM broadcast transmitters supplied by Harris Corporation and others need no tuning to produce their rated output power into a 1.3:1 SWR or less, anywhere in the FM broadcast band 88-108 MHz. Even the harmonic filter needs no changes, and maintains harmonics at -80 dBc or better. They are frequency agile, and can be reset from one carrier frequency to another, anywhere in the FM band with a transition time of a few seconds The overall AC input to r-f output efficiency of these transmitters exceeds 60% (includes the exciter, control system, IPA, and cabinet fans). RF I know this question was directed to Walt, but I'd like to mention that I've designed and built solid state class C amplifiers at the 5 - 10 watt level which have measured efficiencies of greater than 85%. Roy Lewallen, W7EL |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Transfer Impedance(LONG) | Shortwave | |||
Efficiency of Power Amplifiers | Antenna | |||
Matching , Power Transfer & Bandwidth | Antenna | |||
max power transfer theorem | Antenna |