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If anyone besides me is having trouble keeping track of what Reg is
trying to say, maybe the following recent quotes will help. That is, they'll help you understand why you're having trouble keeping track. For what it's worth, I agree with the first quotation of 8/31. But apparently Reg doesn't, even though he said it. Roy Lewallen, W7EL 8/30: Perhaps somebody might be prepared to state the power actually radiated from feedlines in watts. At least it may create the impression you know what you are talking about. 8/30: Roy, do everybody a favour, by stating, numerically, how much power is radiated from feedlines. Then somebody might have some confidence in what you are bafflegabbing about. 8/31: Any current which finds its way on to (3), which ought to flow in the antenna, will result in the coax participating in the radiation pattern of the whole antenna structure. BUT IT IS A SILLY QUESTION TO ASK HOW MANY WATTS ARE RADIATED FROM THE FEEDLINE. OR, CONVERSELY, HOW MANY MICROWATTS ARE PICKED UP BY THE FEEDLINE ON RECEIVE. The feedline cannot be treated in isolation as if it behaves independently of the antenna. For starters, the radiation resistances of the feedline and antenna do not add arithmetically. They interact with each other. 8/31: If you erect a 10 meter 1/2-wave dipole and center-feed it with a 50 feet length of coax, and then transmit on 1.9 MHz, 99.9 percent of available power will be radiated from the feedline and only 0.1 percent from the antenna itself. http://www.smeter.net/feeding/feedpowr.php: Centre-Fed Dipole - Radiation from Coaxial Feedline Author: R.J.Edwards G4FGQ © 25th March 2003 Program Notes .. . . With no loss in accuracy, to simplify the model, the transmitter is located at the dipole centre and the coaxial line is replaced by a single conductor of the same diameter as the coaxial braid. There are 3 radiating elements. Radiation resistance, input impedance, and input current of each element is calculated. Finally, the percent of total power radiated by each of the three elements is calculated. |
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