Radio transmitter circuit  - Page 1
Forum section: electronics / beginners

author: yalect
author_rank: Regular Contributor
timestamp: May 22, 2015, 09:07:26 am
content: Hello,I want to build simple circuit to send binary data one or two regardless what they are, with important distance, some Amateurs use the frequency of 27Mhz and other high frequencies, I am looking for simple Ideas (transistor, Op-amp) especially for the receiver just for getting the base of working such circuits.Thank you

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: May 22, 2015, 10:15:24 am
content: For short distances the small prebuilt 300 or 433 MHz transmitter/receiver modules are good.

author: codeboy2k
author_rank: Super Contributor
timestamp: May 23, 2015, 04:20:08 am
content: You didn't fill in your country, so we don't know where you are.Also you said "with important distance" ... what does that mean, exactly? can you give a quantifiable number, like 10 m, or 10 km ?Generally, each country has it's own regulations regarding the use of wireless transmitters, and have their own laws stipulating which frequencies are available to you to use, and for what purpose. Most (all?) countries require radio operators to be licensed.The well known ISM band (which is not really a 'band' but a group of frequency bands) is available for use without a license (but still subject to government oversight and power limits). The ISM frequencies are not all available everywhere, each country generally allows some but not all of the ISM frequencies to be used inside the country. Check with local laws. According to the Wikipedia entry, FCC part 15 governs ISM use in the USA, ETSI in Europe and (not in the Wiki) Industry Canada in Canada (dumb ass name for a government agency.. at least it's not as bad as the UK's silly ministry names)Bluetooth, WiFi, zigbee, wireless microphones, cordless telephones, RC control, many many more are all found inside the ISM range and so the operator (that's you) doesn't need a license.And the pre-built wireless modules at 300 or 433 MHz that vk3yedotcom already mentioned are inside the ISM group of frequencies (but still may not be legal in your country).As for building something yourself, either for one-off purpose or for a learning experience, then google around for simple FM transmitters in your ISM bands, and then you can use FSK (frequency shift keying) to send ones and zeros in the audio range. This is simple to implement and fairly common for low speed telecommunications (i.e. up to 1200 bps). You can also look up PSK (phase shift keying) which is also just as easy to implement. For higher speed communications it make no sense to build it yourself, as that's a complex beast involving one or more of multiple phases, multiple frequencies, multiple amplitudes and combinations of all of these that I don't even want to get into here.Google AM, FM, PM, PSK, BPSK, DPSK, 8-PSK, 16-PSK, AM, QAM, 8-QAM, 16-QAM, etc, etc, etc,http://en.wikipedia.org/wiki/ISM_bandhttp://en.wikipedia.org/wiki/Frequency-shift_keying

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 23, 2015, 04:38:02 am
content: What country are you in? Please enable your country location in your user profile. Information about wireless products and bands are dependent on what country you are talking about.What does "one or two regardless what they are" mean? That does not make sense in English.What does "important distance" mean? That does not work in English, either. We can't really help you without actual numbers.Do you really want to make something from parts? There are very many transmitter and receiver modules available already built and tested, and they cost far less than if you made it yourself. Are you trying to learn about making transmitters and receivers? Or do you need wireless data transmission as part of some larger project?