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hey people i have to design a highly directive antenna for a direction finding device operating in the 100 to 500 MHz band, can u plz help me out on this.
 

crayon

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What you need is a yagi. There is a ton of stuff out there via google that can get you started.
 

Al42

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A Yagi that's directional over a 5:1 frequency range? Yagi's turning over in his grave. To maintain directivity the antenna must maintain spacing and element length - in wavelengths - and that's not possible over that great a range.

chandramanikumar, what does "have to design" mean? A class assignment? A job requirement?
 

prcguy

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Directional antennas in the general sense are not the usual antenna for direction finding. Antennas that null are used for greater precision in determining the direction. A log Periodic can easily be designed to cover the range you desire but even a high gain version will still have a beamwidth that is too wide for determining a precise bearing.
prcguy
 

SCPD

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chandramanikumar said:
hey people i have to design a highly directive antenna for a direction finding device operating in the 100 to 500 MHz band, can u plz help me out on this.
Have you considered a switched antenna array? This may have the same wavelenghth geometry issues as other types. RF switch cycles through the antennas to an FM receiver - which compares the phases differences. I think Ramsey even has a kit for this.

I'm also wondering if something like an ADF could be made to work in the range - goniometer plus loop and sense antennas.

-rick
 

crayon

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Al42 said:
A Yagi that's directional over a 5:1 frequency range? Yagi's turning over in his grave. To maintain directivity the antenna must maintain spacing and element length - in wavelengths - and that's not possible over that great a range.
:)

The OP specifically asked for a "highly directive antenna". And since one cannot have directivity *and* bandwidth, correct me if I am wrong, that only leaves yagi's, L/P, dishes, et al types of antennas.

I also assumed he really did not know what he was asking for :wink: , and would narrow/lower his DF expectations after doing some research on google about yagi's.
 
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