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"Telamon" wrote in message
news:telamon_spamshield- Whatever the characteristic impedance of the wire is if you stimulate it with energy at some frequency it will react to that energy with a combination of the characteristic impedance and added to that a value of impedance based on the electrical length of the wire. The reactance of the the wire would be the combination of the characteristic impedance and the reflected energy together. Telamon Ventura, California Telaman, Perhaps the fault in my understanding is that there is more than one type of impedance talked about here and in other posts. Perhaps the speaker is talking about one and the listener is listening for the other. In the above paragraph you mention characteristic impedance and impedance based on electrical length. I conclude from your post here that the characteristic impedance always remains the same unless some physical changes are made to the components, antenna or feed-line. Whereas the other impedance (it would be nice if it also had a unique name rather than just other impedance) which is based on electrical length is therefore based on frequency. The introduction of frequency introduces reactance which affects the other impedance, but the characteristic impedance remains the same. If that is the case (please correct if not) then the following should be true: If I have an antenna with a characteristic impedance of, say, 600-ohms, and I have a coaxial feedline with a characteristic impedance of 50-ohms, the two are missmatched and I should use a balun (unun?) with a ratio of 600-ohms to 50-ohms to properly connect the two components. At this time I now have this antenna properly connected to this feedline, and as yet no frequency issues have been addressed. Is this correct? If yes, then it could be said that a balun (unun) matches these two physical devices without frequency of operation considerations. True? I'm not being argumentative, I'm asking. I have a loop antenna whose characteristic impedance I do not know. I want to determine its characteristic impedance. I also want to match it to my receiver (50-ohm nominal input) the best that I can. I ask myself if I need a matching device? These are the issues that I am working on and before I try to tackle the answer, I first want to understand the theory. Thank you. Al KA5JGV |
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