Antenna?

Hi, im new to wireless comunication and i have a project in mind. i want to use a TX-C1 (433.92MHz) transmitter and equiv reciever to send data over 100m. i need to attach a 17.2 cm antenna! now i dont have any knowledge about antenna's and was wondering what type of antenna to use, can i make my own, and where to get them.

thanks

There is a Ham band that includes that frequency. Check the Ham outlets for a Yagi antenna for the 70 cm band. Or you can make your own. Check out the ARRL Antenna Handbook for some easy to build designs.

The 17.2 cm antenna you referenced would be a quarter-wave dipole at that frequency. Just a "whip" antenna. You can make one out of a stiff piece of wire. It won't have any gain or directionality, though, but it might be adequate for your application. 70 cm communication is pretty directional so you might end up with a yagi in the end.

I have used a pcb track about 4 inches long tuned by an smd capacitor (a few pf) and got a range of over 150 mtrs with a handheld transmitter at this frequency.

It took a bit of experimenting with track widths and shapes but when I hit the right tuning, the range increased by over 5 times compared to my first attempt.

How much space do you have for mounting an antenna? Is it going to be on something fixed, or something like a robot that will be moving around and may bang the antenna into trees, furniture, or whatever?

A directional antenna like a Yagi could be a big help, but it could make things much worse if it's pointed in the wrong direction.

I was looking into a 900MHz project a few months back, and found vendors selling homemade PCB Yagis and professional rubber duckies for under $10 shipped on ebay. You might check there, too, once you know what you need.

Ran

Ok, i dont think you guys understand my lack of antenna knowledge ;D I really dont know what to get. Ill explain my project a bit better: i am making a 100m race timer using a laser finnish line, i want to send the data from the sesor at the finnish line back to the start wirelessly. i am using the transmitter and reciever i explained earlier. now i would prefer the antenna to be as small as possible, but i dont need a pcb antenna or anything. is it really important for it to be a specific lenngth(17.2 cm)? or can i find one of those rubber ducky antennas for 433 Mhz? its out in the open so there will probably be good line of sight. please explain what i need exatly and maybe send me a link to what i wshould be looking for. also how sould i connect it to the transmitter and reciever? its just a pin? is there any special thing i need to do? Thanks for the help.

again i have never gone wireless before! ::)

Go for the easy option first, just try a piece of wire 17.2cm long connected as close to the transmitter pin as practically possible, either directly to the pin or via a short length of pcb track.

If it is inconvenient then just trim the length of the wire until the performance degrades to an unacceptable level, but 100mtrs direct line of sight should be easy to obtain.

Edit : the same thing for the receiver as well

Go for the easy option first, just try a piece of wire 17.2cm long connected as close to the transmitter pin as practically possible, either directly to the pin or via a short length of pcb track.

Yeah, what he said.

The next thing to do is add a piece of wire exactly the same length as the antenna, connect it to ground as close as possible to the antenna connection, and point it in the opposite direction. (see dipole antenna)

Then, make sure the antennas are pointed the same direction; if the receiver antenna is pointing up, point the transmitter antenna up. (look up "cross polarization loss" if you want to know why).

Next, try changing the orientation (of both at the same time, in the same way), in case there is some interference source (use cross-polarization loss to your advantage).

-j

any specific type of wire?

Try anything you have already got, if it doesn't work try something else :)