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I am building a wideband dual band omni for school. My antenna is about 2m long. The antenna length basically has two sections (divided by ports) - from 0 - 1.8m (This length is for 20-180MHz) and from 1.8m - 2m (This length is for 500-3000MHz). I have two edge ports feeding each section i.e. port at 0m and port at 1.8m.

I have managed to match for 20-180MHz band, but am struggling for the other band, is there a way to make sure that "port 2" doesnt see the impedance below it - i.e. impedance seen by port1.

How can i go about matching for the other port?

N.B This is all being done in a simulation package "Feko"

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  • $\begingroup$ Have you looked at diplexers? (Too late for your project, I know. I just joined the forum.) $\endgroup$
    – AG5CI
    Commented Jun 6, 2017 at 20:21

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I have managed to match for 20-180MHz band

You will not be able to match a 1.8 meter long antenna to such a wide bandwidth. Since your note says that you are doing this with Feko, I would suggest you are not applying the correct parameters or you are not correctly interpreting the results.

You did not mention the feedpoint impedance to which you are trying to match but this is typically in the 50 to 75 ohm range. Just to get you in the ballpark, a vertical antenna with a height of 1.8 meters with a proper counterpoise to facilitate feeding the antenna, will have a 2:1 SWR bandwidth of <3 MHz and will be resonant at ~40 MHz. You are claiming a 160 MHz bandwidth so clearly something is wrong in your analysis or description.

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