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On Mon, 12 Mar 2007 11:00:04 GMT, Jan Panteltje
wrote: On a sunny day (Mon, 12 Mar 2007 07:36:25 +0000 (UTC)) it happened (Don Klipstein) wrote in : snipped good stuff Not only is increased output stage heating possible and maybe fairly likely, high VSWR also causes a high chance of the output stage seeing a partially reactive load. RF bipolar transistors often do not like those due to increased need to dissipate power with higher voltage drop. As I said above, RF bipolar transistors are likely to really dislike simultaneous higher voltage drop and higher power dissipation. - Don Klipstein ) All true. Also normally, there is a pi type filter (to prevent harmonics), between amplifier and antenna. This filter _WILL_ match the antenna to the output impedance of the transmitter, so _even_ if the transmitter output impedance is very very low (low voltage high current output stage for example), the reflected power will be nicely converted to match the transmitter, and heat up the output amp, with its possible destruction as result. Jan and Don, Both of you gentlemen really need to read Walter's book Reflections (any edition) and put that myth to rest once and for all. Danny, K6MHE |
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