The voltage or current can be as bad as the 1:1 voltage or current multiplied by the square root of SWR – NOT multiplied by directly by SWR. So voltage or current at a 6:1 SWR could be as bad as about 2.5 times the 1:1 SWR voltage or current, and at 10:1 SWR a little over three times the 1:1 SWR values. Note that these are worst-case numbers – and as voltage goes up current goes down and vice versa for a given power level.
Phil – AD5X “Let's assume your tuner is matching a load that presents a 6 to 1 SWR. Let's further assume that you have a 100 watt transmitter. At 50 ohms, 100 watts represents about 70 volts RMS of RF signal. or about 101 volts peak. No problem for a capacitor in the matching network to handle at 50 ohms, but that 6:1 SWR means that the voltage could now be 420 volts RMS or almost 600 volts peak - still not too much of a problem. But, suppose you increase the transmitter power from 100 watts to 1000 watts. The RF voltage at 50 ohms increases to 223 volts RMS, (315 volts peak), and when the 6:1 SWR is taken into account, that voltage is now about 1338 RMS volts, or 1820 volts peak. The same sort of thing happens with currents. At 1000 watts, the RF current at 50 ohms is a little less than 5 amperes. But at 6:1 SWR, there will be places where the current is almost 27 amperes - a significant amount to be sure.” ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
