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On Dec 10, 12:55*pm, " wrote:
I was reading about an Off-Center Fed Dipole *(OCFD) *antenna. The following statement was made: "An effective balun can be made by coiling up coax providing it is self-resonate at or very near the operation frequency" In the above statement, what does "self resonate" mean? Lee *KA0FPJ in that context it means that the coil of coax has distributed capacitance and inductance that at some frequency presents a parallel resonant circuit which makes a high impedance for currents on the shield of the coax. you can see the effects in the table on my web site (http://www.k1ttt.net/technote/airbalun.html) where there are peaks in the impedance of the air core 'baluns'... it is actually more correct to call them chokes than baluns since they really just try to choke off the current on the shield of the coax at the feed point. |