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Tunable HF antenna - request for help

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tang16

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dielectric hf antenna

Hi,

Currently i am designing a simple monopole antenna. My design is something similar to a sleeve antenna. I would like to seek help in knowing what are the dielectric materials that i can use for tuning the monopole antenna.

Thanks for your help.
 

Re: Tunable HF antenna

A “sleeve” is a λ/4 length cylinder, which behaves as a choke to prevents the RF current leaking into the outer surface of the coaxial feeder line.
Usually the dielectric between sleeve and feed cable is air.
You want to tune the sleeve or the monopole element?
 

Re: Tunable HF antenna

Sorry.. I am new at this i would appreciate if you could explain a little to me. I have attached my idea of the monopole antenna.

If i am not wrong it is the monopole element that i would like to be tuned.
 

Re: Tunable HF antenna

This doesn’t look as any antenna that I know. Looks like a discone antenna, but the monopole element shall be in the top of the skirt (or sleeve).
 

Re: Tunable HF antenna

The monopole antenna will be at the top. But at the top it is not a cone therefore i did not think that it is a discone.

Please help me as i am stuck for my project. Thanks.
 


Re: Tunable HF antenna

nope. I understand that discone is a cone at the top but mine is just like the sleeve antenna but i am asked to connect wires down from the top to the dielectric lump elements for tuning purpose.
 

Re: Tunable HF antenna

My opinon is that it will not work.

Are you sure that the center piece is a monopole antenna, and not a coaxial line running up to the top. If you ran coax up to the top, and then ran one wire back to ground from the center conductor, and the other wire from the shield at the top, and then to the ground plane, you would have a (junky) dipole that would receive on both horizontal and vertical polarization. You could use the lumped elements at the end to make it resonate.
 

Re: Tunable HF antenna

My initial design was just a coax but running the simulation without the lumped components, my results was not that good. Thus i changed my design to be this way. I can try to re-design my antenna but i do not know what kind of lumped materials i can use.

Is there any papers regarding this so i can use it as reference?

Thanks for giving me some pointers.
 

Re: Tunable HF antenna

What type of simulation software are you using? An Emag simultor?

For instance, where you are attaching the "lumped elements" is not at "ground", but at some point on a round piece of metal, some distance from the center of the disk. If you are simply modelling those lumped elements as connecting to "ground", you are going to get poor simulation results.


Rich
www.MaguffinMicrowave.com
 

Re: Tunable HF antenna

I am using HFSS for simulation. It is a software given to me to use it.

I was thinking of using lumped elements that can be screwed to the "ground". On the other hand, I do have an idea of placing a board above the ground so that i can place the lumped elements.
 

Re: Tunable HF antenna

Is there any other ways to connect the lumped elements? What are the lumped elements i can use?

Please help me!!!
 

Re: Tunable HF antenna

Hi,

Please help me for this. I have tried searching and i am stuck for it. Please help me. Thanks.
 

Re: Tunable HF antenna

Please help me.. I am rushing for my project and i am stuck. I have found a paper on sleeve antenna with ground wires.

Can someone explain to me what is a λ/4 sperrtopf?

another thing is using HFSS, can i just extend the center of the coaxial cable and treat it as my monopole? [/img]
 

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