Need Help Designing ann Antenna

http://www.rsgb.org/

First step would be to identify what frequency you want the antenna to operate at...

Will it need to be omni-directional or directional?

What gain would be needed? What impedance?

Where is it to be sited? Any large buildings around? What size constraints have you ?

John.

What you need is The ARRL Antenna Book. It will take you through the entire process from idealized specs to construction...

468/frequency Mhz. yields length of a dipole in free space. hope that helps

Perhaps your school has a ham club? If so, join up. Get the ARRL book, as was suggested. And since you need a easy method to test it, focus on a smaller antenna in the FM broadcast band, or the 2 meter ham band. Without a license, you can build a receiving antenna to listen to the local FM radio station without too much difficulty.

But again, the best way to learn about antennas is to invest in a good book by the RSGB or ARRL and get some practical experience via your local ham club.

The only problem I see here is that your professor will likely want to see a bit more than simply a construction project, and so some 'research' work has to be included in your project. This usually means that you are going to choose a design, but vary one or more variables of the antenna in order to optimize it, or characterize it, or acheive some purposeful conclusion or result. You probably know what I mean, so have fun.

Greg

Re testing a project antenna...endeavor to obtain a ''Grid Dip meter". This instrument tests for the resonant frequency of antennas. Not an unusually expensive or complex instrument but do not know how readily available they are now.

Side note; antennas will resonant at multiples of the fundamental frequency, though not as efficiently. This can (easily) be demonstrated by the GDM.

ELH; Cincinnati, Ohio

Hmmmm... Thinking that you are into physics rather than EE, I would say build a random length dipole, and measure it's standing wave ratio at various frequencies. Radio Shack (and others) make a meter for SWR that operates as high as 30 MHz... so I would make the dipole about 7.5 meters from the feed line in both direction. This means that you would need a way to power the antenna. Do they have Citizen's Band in Nigeria? I don't know what you have for lab equipment to work with, but you do need a signal source.

I (as others) will highly recommend the ARRL antenna book for references. The book is kind of spendy. You might want to look in your local (school) library for it. It will give you all sorts of knowlege and ideas for your project... and even though they might not have the latest edition, physics doesn't change.

If you need to order one, try www.arrl.net... who knows?? It might interest you in Ham radio... I have been doing it for the last 50 years.

Bill NW7L

Further to Bill's point regarding physics rather than EE, a student in my final year did a study of how the surface of a microwave feedhorn affects the impedance and the efficiency of this type of antenna.

He had the technicians in the EE lab build several antenna feedhorns, ranging from smooth surface, to sandblasted, to ridged surface (I'm describing the inside of the feedhorn.) The feedhorn had a curved opening, to gradually increase the impedance from 50 ohms to free-space impedance. I can't recall why different surfaces matter, but apparently it does, and this seemed related to more physics than EE.

Perhaps your school has a shop that can machine the antenna, and an anacheoic chamber with appropriate test gear (vector network analyser to measure S-parameters). The EE lab technicians had the antennas constructed as per the student's directions and the student then brought this into the chamber for testing.

Greg VE9GFI

Greg

This reminds me of a story a friend told me several years ago.

When he was in the navy, he was in charge of the radars on an aircraft carrier. Some brilliant soul decided that the island of the ship needed repainted... so the first thing you do, is to chip the old paint off. Suddenly, the SWR on the radar antenna went to pieces. Yup... they had chipped the paint off the waveguide, and in the process had made all sorts of dimples all the way up the waveguide to the antenna. For those who don't know, waveguide is very precisely machined pipe, frequently silver plated on the inside, and very expensive. So "Deck Force" (the people who do painting and such) had to buy a new set of wave guide out of their budget.

They decided that this would not happen again... so they made up a bunch of cute little signs which read "DO NOT CHIP THE WAVEGUIDE". Every six feet up the length of the wave guide, they drilled holes in it, and fastened the signs to it with sheet metal screws.

Guess who bought another set of wave guide...

73's

Bill NW7L

thanks a lot, i really value your advice and i think i will build on it, i was thinking if i could design the antenna then simulate the effect of the antenna with some software, so i will no longer have to construct the antenna physically. i will work on acquiring the ARRL antenna book, i guess i'll have to get to work on dipoles and see how it can be utilized as an antenna. meanwhile i'm going to submit a proposal to my supervisor later today saying that i want to design and simulate of the effects of a dipole antenna.i pray it will be accepted. the specifications have delayed me from submitting a proposal all this while, but my search for the specifications on the internet has not been more fruitful. once again, thanks for your advice.

one antenna design that is inexpensive to make, has vast commercial/private applications and can directly show results with software... is for wireless 802.11

see http://www.oreillynet.com/cs/weblog/view/wlg/448

often referred to as a "cantenna", its a 'yagi' style 'shotgun antenna'.
Same principle as using concave reflectors (satellite dish)
ive seen case studies of this being accomplished over a range >20 miles. they had to do it from elevated endpoints because of the curvature of the earth. costs maybe $20?