Jeff DePolo wrote: > NO. VSWR on a transmission line doesn't directly manifest as "heat" in a > transmitter. The whole notion of high VSWR creating heat in a transmitter > is likely based on a drop in efficiency in SOME transmitters when they are > not properly matched to the feedline.
Or worse, a transmitter that when feeding anything other than its design Z starts throwing spurs. In that case, it's output filters (if it has any!) may be eating all that "spur" power... because folks set power AFTER the final low-pass filter. I could see that being another possible way you'd get "transmitter heating" if things were mismatched. It wouldn't be as significant as the whole PA getting inefficient, though. Jeff also already mentioned (and set aside for purposes of this discussion) transmitters that have built-in directional couplers and loads that are mounted to a common heatsink with the PA transistors. Moto likes to do this on most of their continuous-duty PA's. That can cause "heating" too, if reflected power is high, but it's not relevant to the discussion at hand, because it's not the transmitter heating up, it's the load hanging off of the directional coupler. Nate WY0X
