Guidance for using RF Module

Hello Everyone,

I am making a project in which I intend to transmit data from one Arduino to another using 433MHz RF Module.
But the issue is I want the radio waves to be transmitted in one direction only instead of getting transmitted in 360 degrees. Please help how can I accomplish it.

Thanks in advance.

Sounds like you need a directional antenna, rather than using a simple piece of wire. Any particular reason you want to focus the RF signal in one direction?

It is a bit impractical and the antenna will be a lot bigger. You need to use an antenna called a yagi Understand Yagi Antenna Theory: the Basics » Electronics Notes
I once had a 10 ft long yagi at this frequency for ham radio. It had a beam width of about 20o. The longer it is and so the more elements it has the narrower is the beam width. But there are also nodes off the main beam width, that is areas where the signal peaks but not as much as in the main direction. There is also a peak in the reverse direction.
See Yagi Antenna Gain, Directivity, Front to Back Ratio » Electronics Notes

I am suspecting that this is a lot more complex than you expected, but at these frequencies that is how radio behaves.

You need to explain what it is your are trying to achive.

In reality even highly directional antennas will radiate, at reduced levels, in directions other than the main one where its pointing. And even this main direction will have a direction spread of several degrees.

We can only guess if this sort of direction 'leakage' is important to you or not.

Small amount of

if this sort of direction 'leakage' is important to you or not.

won't matter to me.
A directional antenna will work for me.
Can you please suggest any directional antenna that can be used with the 433MHz module and how can I integrate the antenna with Arduino(like do I need any external power or something else that is different from using the 433MHz sensor without any special antenna)?
Thanks for your help.

You will finds lots of DIY projects for 433Mhz antennas out there, its very close the the Amateur Radio 70cm band, Amateurs do like to build their own stuff.

Most all Amateur radio shops will sell antennas for 70cm.

But you still have not said what your trying to achieve.

I’ve worked on a Ultraviolet transmitter that was very directional. A cutout of the area to be transmitted to was placed over the emitter, measuring how far the transmission went beyond the range of the cutout showed a deviation of about 2 inches beyond the limits of the flight deck of an aircraft carrier.

abcabcxyzxyz:
Small amount of
won't matter to me.
A directional antenna will work for me.
Can you please suggest any directional antenna that can be used with the 433MHz module and how can I integrate the antenna with Arduino(like do I need any external power or something else that is different from using the 433MHz sensor without any special antenna)?
Thanks for your help.

See reply #2. The smallest worthwhile yagi has 3 elements approximately half wave in length on an approximately 1.5 wave length boom. There are other directional antennas, but they are all bigger than that. This is why you see so many yagis and not so many other types.

srnet:
You will finds lots of DIY projects for 433Mhz antennas out there, its very close the the Amateur Radio 70cm band, Amateurs do like to build their own stuff.

Most all Amateur radio shops will sell antennas for 70cm.

But you still have not said what your trying to achieve.

Actually the ISM band it WITHIN the 70 cm amateur radio band.
Paul

I intend to have an Arduino with a transmitter mounted on a rotatable platform. and the receivers are in different directions. The Arduino with the receiver is programmed to ring a buzzer if it receives the signal. The intention is that the player rotates the rotating platform in different directions and the buzzer on the other Arduino rings if the pointer is in its direction.

I wanted to use 433MHz RF because there can be some obstacles between the transmitter and the receiver.

Is there any better way to do that?

and can someone please guide me about the range of this module that I will get?

Thanks

To do what you propose will require similar antennas ob both the transmitter and the receiver. Otherwise the beam width will allow multiple receivers to see the same signal. I have a 432 mHz antenna that just might do what you want it is 18 elements and is about 3 ft long.

In reality, want you are proposing can only be done with very high microwave frequencies, Even way beyond the 2.4 gHz used in the simple Arduino boards people are using. Time to go back and review your physics classes.

Paul

A antenna rotator for 433Mhz antennas is not a simple or low cost bit of kit.

2.4Ghz yagis are real cheap, light and a lot shorter however, so much easier to move around.

The range at 2.4Ghz would depend on the modules, NRF24s might do it, depending on the distance.

2.4Ghz LoRa modules would almost certainly do it, these have long enough line of sight range (tested to 89km) that curvature of the Earth is what will restrict range at gound level.

A 2.4Ghz WiFi Yagi wont cost much, neither would some NRF24s, give it a go and report back

What ever you decide on, be sure to get the graphic report on the radiation pattern of your antenna. That will determine whether it is acceptable or not.

Paul

Can NRF24 Modules transmit the signal in a particular direction?
What is their range?

The NRF24L01+LNA+PA variant has an SMA connector for its external antenna, so I guess you can connect an alternate antenna to give you more directionality. All the other variants have a PCB antenna, I think.

BTW, have you seen the YouTube video of the NRF24L01 30km challenge? It may give you some ideas.

The intention is that the player rotates the rotating platform in different directions and the buzzer on the other Arduino rings if the pointer is in its direction.

There are so many things stopping that from happening, it is just not that simple.
You haven't said what distance they are away, but side lobes and propagation conditions are going to ensure that you will pick up signals from devices you are not pointing at.

There is also a legal requirement, while these devices work in the license free zone there is a maximum ERP ( Effective Radiated Power ) they are permitted to use. Slapping a high gain antenna onto a radio that is transmitting at the ERP limit with a simple ominidirectional antenna is instantly going to make it illegal by breaking the ERP limit.

These things are only license free to operate, you are not permitted to make any adjustment that would change the ERP. In order for you to be permitted to make such a thing you would have to have a ham license, as several people here have.

I don't Intend to increase the output power of the module.

What all I require is that the signal is transmitted only in a particular direction.

Is there any way to block the radio waves from going into other directions? any specific material? or any other way? physics master anyone?

abcabcxyzxyz:
I don't Intend to increase the output power of the module.

What all I require is that the signal is transmitted only in a particular direction.

Is there any way to block the radio waves from going into other directions? any specific material? or any other way? physics master anyone?

Certainly there are ways, but you need to begin to think microwaves and the antennas that are used with microwaves.
Paul

@abcabcxyzxyz

Please do NOT cross post / duplicate as it wastes peoples time and efforts to have more than one post for a single topic.

Continued cross posting has resulted in a time out from the forum.

Could you also take a few moments to Learn How To Use The Forum.

Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.

The radio spectrum you wish to cover is much too wide for a single application.
I would suggest you reconsider your project completely for transmission purposes unless you want to face the wrath of your local radio enforcement officers who would take great delight in stripping your home of any and all technical devices with zero chance of return except in the case of a lengthy and expensive legal challenge.

There exists devices within that spectrum that may be legal in your country and I suggest you take the time and effort to read about them.

Bob ( G1LPR )

abcabcxyzxyz:
I don't Intend to increase the output power of the module.

You miss the point. Putting a yagi on it, will automatically increase the effective output power. The regulations pertain to the maximum radiation, not the aggregate.

You could address that by decreasing the transmitter output power, but as you don't seem to understand RF, it's unlikely that you could achieve that.

Ken (VE3MIX) :slight_smile: