I'm in a little over my head with my latest project. The idea is to use my newfound knowledge of analog circuits, transmitters, receivers and the like, to build a communication network. So I have two devices, with arduinos, transmitters and receivers inside them, transmitting digital data with basic AM to a central antenna, which will be in say, the middle of the room. The central antenna receives the information, and simply conveys it to all devices at once. One person will receive their own message. The devices demodulate, and take in the serial data from the central antenna and convert it into a message on the LCD screen, powered by the arduino! It's a basic texting service for free. The service that is.

Now you have an understanding of the system, here's what I need to understand:
How can I use one antenna for both transmitting and receiving?

I mean, I could use two antennas, but why waste the resources? How do repeaters do it? That's what I want right? A repeater? I'm fairly naive in transmission links.

Thanks. -Sam Gallagher

 

On second thought, sorry to double post, but say my range is 1 mile for this system. Is a central antenna even necessary? I mean, if the tower is within a mile of you and so is every other phone should I just forget the middle man? Wouldn't that make the cell phones super clunky? Would they have been clunky anyway? Or maybe is the central antenna good because it can see every phone, while the phones can't see each other?

 

Duplexers enable the simultaneous transmission and reception of signals on a single antenna. The duplexers that I am familiar with are for FM and require slight offset of the transmitted and received signals' frequencies.

 

Duplexer if your transmit frequency is close to your receive frequency.

Diplexer if the two frequencies have some decent amount of separation.

 

Do you need to use duplex transmission? I'm guessing not, so you can transmit and receive on the same frequency and same antennas, using time slots to poll multiple remotes from a central location. (in the trade, this is called simplex operation).

 

Interesting info, thanks guys. I've heard of duplex before I can't believe I didn't think about that! Simplex on the other hand is pretty new to me. I've heard of time multiplexing, but also didn't think to implement that either. Thanks everyone.