Need help in building RF transmitter.

[Darkbyte]

Second year EE student here. I am doing a project which involve the

usage of microcontrollers , lcd display and sensors.

Currently i am having problem with the RF transmitter as I never

make one before.

This RF transmitter that I am going to make is like this :

The transmitter must be at logic '0' when it is idle. give out a

pulse of logic '1' (signal) when a button is pressed.

Receiver :

When it receive a signal (pulse) , it will send another signal to a

micro controller.

Right now i only need to send/recieve one signal out using the

transmitter and receiver , but i might need to send two or more

signal out together if i have a change in plan.

So I need help/guide in making this RF transmitter and receiver.

I had read various forums and website .

Based on my understanding ,

Transmitter = Produce [Waveforms(Frequency) AC Electrical Signal]

--> Produce Radio wave.

Receiver = Using Conductor --> Get the Radio Wave--> Electrical
Signals --> Depend on the Signal waveform --> Transform into what
ever you want.

For the mode of transferring signals, I will be using FM.

For the modulation of signals , I know there is something call FSK

, FDM and Manchester Coding.

Now I will come to the portion that I don't know.
Encoding and Decoding.

I had observed from various RF diagrams , I think "many use micro

controller because it help them to 1) Generate Different Waveform ,

2) It will help the receiver to determine what to do if it receive

signal of a particular Hz."

It would help if someone can post a basic diagram of RF circuit if

you have , and from here I will learn more about RF and configure

it to serve my needs.

Thanks all ,
From a noobie:sad:

 

[betwixt]

You have a lot of learning to do!
Firstly, you cannot just "give out a pulse of logic 1" because RF is not logic. Suggesting it sits idle and sends nothing for a logic 0 while waiting for a button to be pressed means your receiver hears nothing from your transmitter so it has no terms of reference to work with, for example, do you want "nothing" to come out of the receiver until the button is pressed or do you want a logic 0 to come out. Given that you only have two logic states, what do you imagine a "nothing" looks like? If you were a receiver waiting for a pulse from the transmitter and there was a lightning storm nearby, what would happen when it produced a pulse of interference? Could it distinguish an interference pulse from one you transmitted?

You then contradict yourself by saying you will be using FM which has no amplitude difference between a 0 and 1 anyway.

I suggest you do some research on RF data transmission to understand why it's done the way it is and see the limitations of AM, FM and FSK then you will understand why it is necessary to encode and decode the data you are sending. It is a complicated subject and one which frequently confuses people and results in some lively discussions on Edaboard.

Brian.

 

[lurchman]

Darkbyte,

My advice is don't even attempt to build an RF setup from scratch. There are quite a few UHF ISM band systems that you just connect to your PC with the minimum of fuss (google "UHF ISM Radio Modem" with either RS232 or RS432).

The important thing is that these units are "type aproved" in most parts of the world so you are not going to hit up against "licensing requirments" (You are not allowed to radiate signals without a licence or an excemption from your countries radio authority).

---------- Post added at 23:18 ---------- Previous post was at 23:17 ----------

Darkbyte,

My advice is don't even attempt to build an RF setup from scratch. There are quite a few UHF ISM band systems that you just connect to your PC with the minimum of fuss (google "UHF ISM Radio Modem" with either RS232 or RS432).

The important thing is that these units are "type aproved" in most parts of the world so you are not going to hit up against "licensing requirments" (You are not allowed to radiate signals without a licence or an excemption from your countries radio authority).