Now that I have gotten back into radio design I am wondering what gives rise to an antenna's impedance. It couldn't just be the dc resistance as measured by an ohm meter and so it must be reactance.
And I would guess it's a matter of capacitive reactance in that: the longer a wire is, the more capacitance it displays. With this in mind, reactance displays different amounts at different frequencies.
And yet there must be more to it in that Yagi arrays are geometric, not just a length of conductor. Or are they?
This question came up when I pondered making a transmitter to feed a 75 ohm coaxial cable and I realized this fed a 50 ohm antenna which then requires a resistor pad to match them, but the big question then came up: Why is an antenna 50 ohms in the first place?
And I would guess it's a matter of capacitive reactance in that: the longer a wire is, the more capacitance it displays. With this in mind, reactance displays different amounts at different frequencies.
And yet there must be more to it in that Yagi arrays are geometric, not just a length of conductor. Or are they?
This question came up when I pondered making a transmitter to feed a 75 ohm coaxial cable and I realized this fed a 50 ohm antenna which then requires a resistor pad to match them, but the big question then came up: Why is an antenna 50 ohms in the first place?
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