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Looking for schematics of 4km Range FM Transmitter

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richmon74

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4km fm transmitter

i need to make an FM Transmitter that will cover 4km radius. Is anybody with such a schematic and is willing to share? links could be useful.

i ran into the page in the attachment below (i can't get the link to that page online anymore that is why i had to post it) and i'm ready to use the circuit there but antenna is my prob. I dont know about antena designs but a guide could make so much good

the linke to the design of their antenna in the page is'n alive so i want someone to help me go through a design of antena to suite the schematic there

N/B: i am very bussy i wouldn't want to go through the stress of reading on antenna design now.
 

mr_ghz

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Hi richmon74

I see following possibilities for your antenna:
1.) Using a lambda/4 antenna. This antenna has a pattern similar to a donought cutted in the middle. I think it is useful for broadcasting FM radio. It is built of two parts: a good ground (earth) and a wire with the length of 1/4 of lambda. In your case (100 MHz) the length will be about 0.75m. This wire has to be orthogonal to earth. At the feedpoint you connect a coax directly to earth and this antenna (inner conductor). On your transmitter you can connect this cable without a balun to C11 (without C12). The impedance of this antenna is near the output impedance of 75Ohms.

2.) Using the suggested dipole. To build this antenna you use a wire (about 1mm diameter) with then length of lambda (3 meter). You create a form looking like the one in the page. The distance between the upper and lower wire should be some cm. The complete antenna will have a length of about 1.5 meters and uses the described balun to connect. This antenna has a little bit more gain (= range) than the first one.

3.) Using a Yagi. This is a directional antenna. So only people inside this area can hear your signal. Is this what you want?

Bye
 

richmon74

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mr_ghz said:
3.) Using a Yagi. This is a directional antenna. So only people inside this area can hear your signal. Is this what you want?

Bye
actually i would like it to cover a circullar radius of about 4km
 

Borber

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j-pole

Use j-pole antenna. There is a lot of projects for fm on the web.
 

richmon74

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Re: j-pole

Borber said:
There is a lot of projects for fm on the web.
that's true but funny enough most of them don't work
 

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