Help with 433Mhz Transmitter, Receiver, Simplex comms and Nano (30 m range)

Hi folks, noob to the forum. A little background. I am trying to make a remote vibration sensor to attach to some fence panels to detect when a wiley fox bounds over it. I have other projects in the offing to complement this one, but all projects require some sort of RF comms.

So I bought a Nano, an mx-fs-03v transmitter and mx-05 receiver like the ones here 433mhz wireless modules mx-fs-03v & mx-05

I soldered some quarter lamda antennas to either boards (1 per each) as the range was pathetic without.

Now with both boards running from the Nano VIN/GND pins, the transmitter on PIN12 and the receiver on PIN11, using the RadioHead library I can successfully send a “Hello World” and receive it in the serial monitor of the Arduino IDE, thanks to the sketches here RF 433MHz Transmitter/Receiver Module With Arduino | Random Nerd Tutorials

All good. Except that the range is pathetic. I mean 6ft max.

The antenna are like these https://www.amazon.co.uk/Youmile-10-Pack-antenna-Helical-Raspberry/dp/B07QGQ1VG5/ref=sr_1_3?dchild=1&keywords=433+antenna&qid=1597778542&sr=8-3

Now I read that the transmitter will take up to 12v and I tried supplying 12v to the pins on the transmitter from a bench power supply, with the data line coming from the Uno pin 12 but this didn’t work. I guess they need to be all on the same common earth so maybe the solution here is some sort of potential divider to supply both boards with different voltages?

So my questions are :

  1. Is this pathetic range around what you would expect for using the Nano as the power source for the transmitter?
  2. Can this be improved without supplying more juice (I want this to be battery operated so every coulomb counts!)

I think that’s it. Yup. For now :slight_smile:

OK flame me. :wink:

Yes, your 2M range is terrible.

These are not 1/4 wave antennas:


They are inductively loaded broadband monopoles.

I've never had to use more than 5V on a transmitter, and have had successful comms over about 30M (100ft.) with the simplest, cheapest modules and a simple wire antenna. You might have receiver desense problems. Please post detailed images of your entire hardware setup.

Oh, and... what 30M are you referring to in the thread title?

The simplest, decent antenna is 17 cm of straight wire on both the transmitter and receiver ANT terminals.

Much better, use a balanced dipole. I get at least 300 m range, line of sight, with the ones shown below. 34 cm from tip to tip. Connect one inner end to ANT, the other to GND (yes, GND, the other antenna terminal).

I agree but I think something else must be going on as well. Hence I would like to see the setup.

Wavelength is C/F, C=speed of light (meters per second), F=frequency in MHZ.
299.7925 / 433 = 0.692m. /4= 0.17m, or 6.811 inches.

I have little experience with 433 MHz, but I found that the range was from a couple of feet to over 500 ft. Just from plugging in different transmitter modules. I suspect that they aren't precisely tuned when they are manufactured.

You could also use LORA, but I have zero experience with that mode.

I have used several dozen transmitters, different types. All of them had a decent range. They don't need tuning because they are crystal controlled or SAW filter based. Precise tuning is not necessary because the receiver bandwidth is quite wide.

Any antenna that you use, will be affected by all the ground circuit of the transmitter because it becomes the current counterpoise for the antenna, and will in fact radiate and possibly detune the antenna. Since the modules and wiring can have an effectively random geometry as far as 433MHz RF is concerned, it becomes very trial and error, and hard to reach definite conclusions about how the different components are affecting the radiation. The system in reply #2 utilizes it, rather than fighting it, by providing a tuned counterpoise (which will radiate most of the counterpoise current). However most (many?) applications don't have space for 34cm long antenna systems.

aarg:
Yes, your 2M range is terrible.

These are not 1/4 wave antennas:


They are inductively loaded broadband monopoles.

I've never had to use more than 5V on a transmitter, and have had successful comms over about 30M (100ft.) with the simplest, cheapest modules and a simple wire antenna. You might have receiver desense problems. Please post detailed images of your entire hardware setup.

Oh, and... what 30M are you referring to in the thread title?

They are listed as :

"10pcs 433MHz antenna Helical antenna Remote Control for Arduino Raspberry pi"

If they aren't suitable for longer range then fair do's.

I am referring to the same 30m you are, but with a lower case m for metres :wink:

Photos coming...

Attach an image. Right click on it, copy the link address, edit the post and paste the link as an image:

jremington:
The simplest, decent antenna is 17 cm of straight wire on both the transmitter and receiver ANT terminals.

Much better, use a balanced dipole. I get at least 300 m range, line of sight, with the ones shown below. 34 cm from tip to tip. Connect one inner end to ANT, the other to GND (yes, GND, the other antenna terminal).

Will give this a go. Also will read up on those terms you give in your erudite reply. :slight_smile:

Wow, that antenna is small. I had no idea they were so tiny. :slight_smile: :slight_smile: The solder join on the antenna looks cold. It's a long shot, but it could be a problem.

Is the receiver module anywhere near the Arduino when it's operating? The digital noise from the processor can interfere. That is why I asked for "the setup".

And the transmitter.

Note I am constrained to 1 post every 5 minutes.

jremington:
The simplest, decent antenna is 17 cm of straight wire on both the transmitter and receiver ANT terminals.

Much better, use a balanced dipole. I get at least 300 m range, line of sight, with the ones shown below. 34 cm from tip to tip. Connect one inner end to ANT, the other to GND (yes, GND, the other antenna terminal).

I must be doing something wrong still. I soldered on the 17cm straight wires, one to ANT, one to GND for both boards and arranged them like the picture (unless there is something subtle I am missing)

Still the range is attrocious. Can't get from one side of the kitchen to the other.

I got it working after trying some things out. Basically what I learned is that the antenna pin and the ground pin are too far apart to use as the starting points for the dipole. The shape of the dipole is very important, as important as the lengths of each leg.

I managed to receive signal through walls and ceilings, and in direct line of sight it was farther than the length of my kitchen diner so we're getting there.

This dipole is the best of all the types of antenna I have tried, although there is an article on instructables about a "loaded coil" which is 53mm in total length : 17mm straight, then 16 turns round a 2.5mm form and then straight again for the rest of the run up to 53mm. So you get a much smaller form factor, and the "loaded coil" acts as an inductor to damp the resonance and home in on the signal. Would this coupled with a counterpoise be even better than both? Or is dipole the way forward? If I have to have a 34cm aerial then so be it.

It would take no time at all for you to test the two types of antennas.

Paul

search term: 70 cm antenna. the Part 15 ( unlicensed ) band is contained within the 70 cm ham band, so there are hundreds of DIY antenna designs on the web

in terms of effectiveness:

  • Marconi antenna. vertical 1/4 wave ( 17 cm ) with a horizontal 1/4 wave disc. or larger, at right angles
  • 1/2 wave dipole, illustrated above. two 17 cm conductors, in a line
  • collinear: a stack of Marconis with phasing harnesses in between. hard to describe, easy to build. up to 15 db gain. anybody who claims more is not truthful.

those are omnidirectional, if used vertically. the half wave dipole is bidirectional if used horizontally

the easiest directional antenna to build is the Yagi. hundreds of DIY yagis on the internet

if you are setting up a one to many link - one central station, stations at the corners of a large property - a collinear at the base station and yagis set vertically at the corners is your best bet

Thanks so much for the images. That looks pretty much okay. I was hoping to see close ups of the antenna wire connections to the modules, to make sure you attached them to the right pads.

Also, you should test it in a different location. There might be some local interference.

Didn't read past first post, forgive me if I missed important details but...

Those green receivers SUCK, with a capitol S, U, C and K (and one could add a few more letters to some of those for emphasis...). Get an RXB-12 or RXB-14 on ebay. They're like a buck a pop, and are WAY THE HELL BETTER than those green things. 20-50x the range, and they don't lock into a non-functional state when used at short range like the green trash ones do.

The cheapo green transmitters are fine.

Those springy antennae are terrible too. Absolute trash. I couldn't tell you why, I'm no RF engineer, but they sucked in my tests. Almost worse than no antenna at all. What I do is cut up ethernet or telephone wires with the solid-core wire, cut to the appropriate length (what, 17.3 cm?), strip one end and solder in place.

Got ~1000' range with green cheap transmitter and RXB-12 that way, even with my halfassed non-optimized "AzzyRF" OOK protocol. Probably could have done more if I had a longer line of sight...

And a wiley fox? You should be good... I'd be nervous of any sort of gadgets around a wiley coyote though, that never seems to end well...

Paul_KD7HB:
It would take no time at all for you to test the two types of antennas.

Paul

But knowing what is expected might help the debugging process, otherwise a fail is a fail and possibly an opportunity missed.

Extremely useful. You are entirely correct. The transmission will be sending information collected from a vibration sensor. There will be one unit per fence panel. Any vibrations in the panels cause by a fox jumping over will be relayed to my base station and appropriate counter measures can be taken such as making lots of noise, flashing (lights I mean) and possibly sprinkling water at high pressure in pulsed random bursts.

The prototype this evening with a model fence panel, using the dipole to transmit and receive was superb. A centipede's footsteps would register.

I am going to experiment with accelerometers also as I think the 3 dimensional movement and magnitudes therein may help with suppressing false positives.

I am a software engineer by trade so some cheeky AI pattern recognition stuff to learn the profile of an animal versus say a gust of wind. All I then need to do is simulate a fox climbing over. That's a challenge for another day.

Thanks all, a great welcome to the forum. X

you do know about a wolf fence.

in the real world, a wire strung banjo string tight 2 or 3 inches above your fence. 99 percent of a male wolf clears the wire.