How Can I Transmit To Certain Frequency Using RF Transmitter?

Arduino noob here, trying to make me a short ranged radio/transmitter. Don't really know about anything I'm doing and I'm just learning as I go.

I recently purchased these: Amazon.com: UCEC XY-MK-5V / XY-FST 433Mhz Rf Transmitter and Receiver Module Link Kit for Arduino/Arm/McU/Raspberry pi/Wireless DIY(6-Pack): GPS & Navigation

I am trying to figure out how I can use the transmitter to transmit a signal at a certain frequency. I don't wish to use the receiver, but rather my radio instead to detect the signal.

With the transmitter I also tried to replicate the results I got by following this post Turn your Arduino into an AM radio transmitter! - Exhibition / Gallery - Arduino Forum , but I am not able to.

Anyone can lead me in the right direction, as well as can post any sort of documentation on radios and such that I could read?

Edit:

I apologies for the late reply and vagueness of my post. The original idea of the project was to make a one way radio of sorts, where I could transmit morse code. My design was to have a button that is pushed, and then a sound is transmitted. I was able to set up my initial design and use the wire as a transmitter, but the signal was too fuzzy and had little to no range (assuming what I heard was actually from the transmission and not some other source).

I am aware of the legal aspect as well. I am trying to transmit at a distance of at least 6 feet, but not for miles for anything the size of a building. It's just a small project.

I've tried to research what I am trying to do, but there's a lot of varying information and couldn't exactly find anything concrete. But that could just be due to my lack of understanding on the subject. If anyone could help me out, and or point in the right direction, that would be great.

To receive signals on "your radio", you need a transmitter that generates a compatible frequency. What is "your radio" and what frequencies can it receive?

The 433 MHz transmitter modules from Amazon are not tunable, and generate, as you might guess, 433 MHz signals.

Read that forum post you linked to over and over until you understand what it says. You are missing the key to the whole thread.

Paul

Kuroodo:
I recently purchased these: https://www.amazon.com/gp/product/B017AYH5G0

I am trying to figure out how I can use the transmitter to transmit a signal at a certain frequency. I don't wish to use the receiver, but rather my radio instead to detect the signal.

Rather than assume the forum knows what you are actually trying to do, can you explain exactly what your project is.

The forum has no idea at all what "my radio" is, and I suspect its critical for us to know.

I am trying to figure out how I can use the transmitter to transmit a signal at a certain frequency.

Relax the answer is simple. You can’t, and even if you could it would be illegal. So that is your problem solved.

even if you could it would be illegal

Perhaps, if the OP happened to live in one of certain countries.

There are quite a few countries in the World where it is perfectly legal to transmit, unlicensed, in the 433Mhz region, the UK is but one example.

Power restrictions and duty cycle restrictions do normally apply.

srnet:
There are quite a few countries in the World where it is perfectly legal to transmit, unlicensed, in the 433Mhz region, the UK is but one example.

But if you want to modify the transmitter to work at an unspecified "certain frequency" with an unnamed "my radio" you could easily end up on the wrong side of the law.

Steve

srnet:
There are quite a few countries in the World where it is perfectly legal to transmit, unlicensed, in the 433Mhz region, the UK is but one example.

Power restrictions and duty cycle restrictions do normally apply.

But OP says he wants to make them transmit at “a certain frequency” - and unless that frequency is 433Mhz (in which case any of the countless tutorials will work), he will be disappointed, as they can’t be modified for that purpose (or, not without careful hardware modification, replacing the SAW filter and crumb-sized passives, the correct values of which would require someone far more experienced with RF design than I).

But he’d probably less disappointed than if he had made it transmit at a different frequency and annoyed an uptight user of the spectrum he was now illegally interfering with who reported him to the relevant authorities.

Anyway - hopefully he just want’s to transmit between 433MHz receivers and transmitters, and is doing a poor job of explaining what he wants. Clarify your objectives, and we might be able to help.

As an aside, those green receivers are pretty poor. Range is terrible, and you need the full 5v for it to work (ie, no 3.3v). Search ebay for RXB12 (RXB14 is good too, smaller, more expensive, and only 1 data pin instead of two so not a drop-in replacement), or other receivers based on SYN470/SYN480. These get range about an order of magnitude better, and work beautifully on 3.3v, should cost around $1 each. The cheap green transmitters are fine, on 5v or even below that, though the STX882 is comparable at 5 and better at lower voltages.

DrAzzy:
But OP says he wants to make them transmit at "a certain frequency" - and unless that frequency is 433Mhz (in which case any of the countless tutorials will work), he will be disappointed, as they can't be modified for that purpose

Yes, I am aware that the modules in the original post are not normally tuneable.

I am aware that the modules in the original post are not normally tuneable.

And making them tunable, even within the permitted license free zone results in something that is illegal to use in the UK and most other jurisdictions.

This is because all transmitters for license free bands must be "type approved" which involves expensive testing at a professional approved test house. Any modification to the circuit renders that type approval null and void.

I apologies for the late reply and vagueness of my post. The original idea of the project was to make a one way radio of sorts, where I could transmit morse code. My design was to have a button that is pushed, and then a sound is transmitted. I was able to set up my initial design and use the wire as a transmitter, but the signal was too fuzzy and had little to no range (assuming what I heard was actually from the transmission and not some other source).

I am aware of the legal aspect as well. I am trying to transmit at a distance of at least 6 feet, but not for miles for anything the size of a building. It's just a small project.

I've tried to research what I am trying to do, but there's a lot of varying information and couldn't exactly find anything concrete. But that could just be due to my lack of understanding on the subject. If anyone could help me out, and or point in the right direction, that would be great.

I am aware of the legal aspect as well. I am trying to transmit at a distance of at least 6 feet, but not for miles for anything the size of a building. It's just a small project.

The range simply does not matter in Europe, it is the fact you do it at all. Of course there is less risk of being caught but it doesn't alter the legality of the situation, and you could interfere with emergency services or the military.

If you want to do this then do it legally and get yourself a ham license, plenty of websites for that. Choose one for your country.

I am in the US.
According to the FCC, it is permitted to broadcast at AM and FM without a license as long as the device is low powered (in the case of arduino, that's just 5v), and with a range limited to I think 150 feet (way beyond what I want or need). The transmitter will also be set up on my college campus with permission.

Edit:
Just to add, I am understanding radio frequencies better and it seems as I was confused with the modules I purchased. I had originally thought that the transmitter can transmit up to 433 MHz instead of at 433Mhz, and that transmitting something to any radio would have been as simple as wiring it together. I don't have any specific (legal) frequency I wish to transmit to. I am just looking to transmit at any workable frequency, although anything in the KHz range would be best.

Stick to AM radio band and you will be fine. Gammon's project will work.

The transmitting frequency is rather moot if you don't have a receiver capable of receiving and demodulating the signal. The transmitter and receiver must operate at the same frequency. Here in the US it is the 915MHz modules.

I recall a little FM transmitter that was plugged into a 3.5mm audio jack of a cd player or similar and would broadcast the signal to a car radio at the low end of the FM band. It had limited distance.

Then there was a microphone that basically did the same. I recall the TV commercials from the 80's.

Kuroodo:
According to the FCC, it is permitted to broadcast at AM and FM without a license as long as the device is low powered (in the case of arduino, that's just 5v), and with a range limited to I think 150 feet (way beyond what I want or need).

Not quite, the FCC regulations on home built transmitters are here:- FCC regulations.pdf
Read it, and you will see their are some very specific power restrictions, it is not just range. In order to transmit legally you have to be able to verify your transmitter works to those specifications, can you borrow the test equipment to verify this? Do you know how to use it? Basically they don't want you transmitting at all but have to let you for constitutional reasons, so they make it almost impossible to do.

The fact that the Arduino is only powered by 5V is irrelevant, it has little bearing on the power.

The transmitter will also be set up on my college campus with permission.

This is irrelevant.

tinman13kup:
I recall a little FM transmitter that was plugged into a 3.5mm audio jack of a cd player or similar and would broadcast the signal to a car radio at the low end of the FM band. It had limited distance.

Then there was a microphone that basically did the same. I recall the TV commercials from the 80's.

In the UK and Europe these only became legal in 2006, see 2006 change to the law to allow the use of low power fm transmitters for mp3 players

Good news, after some more research and trial & error, I was able to get some results using the Gammon example! I'm still trying to understand how some of this works, but I'm finally on the right path again. After I get my initial design set up, I will try to figure out how making a very short range antenna works.

Thank you for everyones insight.

I'm still trying to understand how some of this works,

It works by generating a square wave. These contain an infinite number of odd harmonics so they transmit over all frequency bands and interfere with everything else.

I will try to figure out how making a very short range antenna works

The antenna need not be short range in fact the better it is the less crap you have to splat all over everywhere to get the range you need. You are best using a long length of wire, the longer the better.

The transmitter will also be set up on my college campus with permission.

I bet the person who gave you that permission hasn't got a clue to the ramifications of your experiment, it is possible he will lose his job as well.