Hi,
I'm trying to build a very basic wireless transmission system. I plugged my antenna
to one of the arduino pins and set it to high, but the receiving antenna
doesn't respond. It is supposed to turn a led on.
I'm using a 10cm wire for both antennas and put them very close to each other.
Do I need an amplifier for this? What else is necessary?
I plugged my antenna to one of the arduino pins and set it to high,
That will not transmit anything.
You can not make a legal transmitter with an Arduino. You can not even make a illegal one doing what you did.
You need this in your setup function
pinMode ( pin1, OUTPUT_RADIO );
You can't make a wireless transmitter or receiver with an Arduino without adding some extra modules. You need to generate radio waves by means of very high frequency ac being fed into the aerial.
Have a look at this: http://www.instructables.com/id/RF-315433-MHz-Transmitter-receiver-Module-and-Ardu/
Russell.
You need this in your setup function
Really Ken, do you think the OP has the slightest idea you are joking ? (don't get me wrong, it IS funny 
)
You need to start your post by defining your criteria. (DESIGN CRITERIA).
This is list of criteria or specifications which identify the requirements of your system (such as range or power, or even frequency, or data transmission rate, or data type etc. etc. etc.) You gave us nothing.
My first thought is somebody's reference to "taking the piss"
Taking the piss
Is this a joke ?
I just need to get 20mA to turn on the led at the receiver.
I tried to send the data using pulse-amplitude modulation by switching the pin high/low periodically. I changed the frequency several times, but I'm not sure which frequency should I use(it's just a small test, so I don't have any specific requirements).
In analog transmission, It would be necessary to send a sinusoidal wave to the antenna modulated with my signal.
In this case, I send pulses to the antenna. Is this enough to transmit a digital signal?
Do I need a band-pass filter at the receiver centered on the transmitting frequency? What about an amplifier?
Is the arduino power enough to transmit the data?
Hope it's clearer now.
In analog transmission, It would be necessary to send a sinusoidal wave to the antenna modulated with my signal.
You don't have a transmitter. I piece of wire connected to a digital output is not a transmitter. That's the extent of my RF experience. You need a transmitter. (and a receiver), neither of which you have , yet.
raschemmel:
You don't have a transmitter. I piece of wire connected to a digital output is not a transmitter. That's the extent of my RF experience. You need a transmitter. (and a receiver), neither of which you have , yet.
The only thing PAM modulation does is to send pulses to the antenna periodically, right? There is not a sinusoidal carrier like in analog transmission. I don't get what else is necessary.
You need something to create an RF field i would imagine. As I said, RF is not my area of expertise, but I am fairly certain you need a transmitter and a receiver.
I think you might be skipping a few steps:
PAM TRANSMITTER
Thank you raschemmel, I'll read it carefully.
I thought it was enough to send the pulses because the transition low-->high would generate an electromagnetic field that would excite an instantaneous current at the receiving antenna.
I thought it was enough to send the pulses because the transition low-->high would generate an electromagnetic field that would excite an instantaneous current at the receiving antenna.
Generating an EM field is not that simple. It requires a knowledge of magnetics and cores .
endrien:
Thank you raschemmel, I'll read it carefully.
I thought it was enough to send the pulses because the transition low-->high would generate an electromagnetic field that would excite an instantaneous current at the receiving antenna.
You really need to learn what Radio is.
Suggest deferring your present project while you do some study on what Radio actually is.
A lot of material is available, just offhand this might be a good reference.
Paul__B:
You really need to learn what Radio is.Suggest deferring your present project while you do some study on what Radio actually is.
A lot of material is available, just offhand this might be a good reference.
Thank you for the advice, Paul. I have many questions on this topic.
In AM/FM systems, we use a carrier to make the signal propagate as EM waves by feeding the antenna with a harmonic signal.
I'm not sure how things works on the digital world. How can I make a digital signal propagate as EM waves? Should I send it as a sine wave? like i(t) = A*sin(wt) ; where A is the symbol?
endrien:
I thought it was enough to send the pulses because the transition low-->high would generate an electromagnetic field that would excite an instantaneous current at the receiving antenna.
A pulse consists of lots of harmonics, each harmonic is a sin wave. Therefore, if you send a pulse to an antenna you transmit on hundreds of frequencies at the same time. This is why it is illegal to do this. You can interfere with lots of radio communications. Or you could if you had a clue about what you were doing. Fortunately you do not, so I think it would be irresponsible of me to inform you how to do this.
endrien:
In AM/FM systems, we use a carrier to make the signal propagate as EM waves by feeding the antenna with a harmonic signal.
That's right and for digital transmission you stil need a carrier (RF sine wave signal) which is modulated by one of many different means, AM, FM, PSK, QAM, etc. As Paul said, you need to first understand what radio is. You could use one of the many ready made modules but it would help to do a little study.
Russell.
russellz:
As Paul said, you need to first understand what radio is. You could use one of the many ready made modules but it would help to do a little study.
Yes, it is not a matter at this stage, of asking questions.
You need to study what Radio is, and any remaining questions you have after you understand the concept will make sense, rather than simply spouting random technical terms! 