I want to design a device which receives basic text wirelessly, and outputs this text on a display. Using Wi-Fi is not a option. I have an idea that it would be possible to do this using FM frequencies. Would it be possible to make the text into some sort of analoge format, send it via FM, and then decoding the information in to text-format again?
closed as unclear what you're asking by Chris Stratton, ThreePhaseEel, Daniel Grillo, Dmitry Grigoryev, Voltage Spike Nov 22 '16 at 17:58
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You can use basic radio modules like these: -
These happen to be from a company called RF solutions but there are plenty of people supplying them.
The tricky part is packaging the data (that you wish to send) into a data stream format that makes a reliable FM system (well, as reliable as radio can be). This requires transmitting and receiving/decoding: -
- A identifiable preamble
- An address
- A checksum
And you do need all of the above for best reliability because, in the absence of a proper data transmission, the FM receiver will be hunting around for anything that might be a signal and this generally means noise: -
That's where the real work lies. So choose your modules based on: -
- Modulation method (assumed to be FM)
- Carrier frequency (country dependent)
- Transmit power (affects range that the link will work over)
- Data rate - lower data speeds usually are more reliable for a given output power and range.
And good luck.
FM stands for frequency modulation. It is a modulation scheme, not a frequency range.
Yes, you can send data over radio waves using FM. However, starting out by deciding the modulation scheme is jumping into the middle. It's like designing a car and starting out deciding the diameter of the spark plug thread instead of specs for what you want the car to do.
Step back and decide what you actually need this radio link to do. What bit or byte rate? What reliability? What to do on error? Just display bad data temporarily, then overwrite it with the next data, or is it better to display nothing when bad data is received? Must the sender know the data has been received? What distance? Is the receiver and/or transmitter power budget tight? What kind of antenna can you tolerate?
There are many question to answer before the low level modulation scheme makes any sense to talk about.
In order to select a suitable solution, you must know the answer to these questions:
- What RANGE do you want this to operate reliably?
- What SPEED will you need to transmit the information?
- What FREQUENCY bands are available in your location (depending on what country you are located in)
- What CIRCUIT will you be using at the transmitting end? At the receiver? There are many microcontroller boards which have integrated wireless.
- What is your BUDGET? You can find assembled and tested transmitters and receivers for almost less than US$1 and up to 100s
- What are the REQUIREMENTS of the project? Is this a formal coursework project? Are you required to design and build your own transmitter and receiver from scratch? Or are you allowed to purchase commercial solutions?
- What is the EXPERIENCE of your team? Are they up to a sophisticated RF transmitter and receiver design and construction?
- What EQUIPMENT do you have to work with? Do you have test gear for working on RF circuits from scratch? Or do you need to rely on pre-tuned commercial transmitter and receiver boards?