Arduino RF range 433mHz

I've bought some of those cheap RF links and I'm really struggling to get reasonable range.
I've been going through forums and I've tried the 17.3cm antenna with virtually no luck.
My range is a few centimeters at best.

One thing to note is I have one of these:http://pages.ebay.com/link/?nav=item.view&id=201273134725&alt=web

Which seems to use the same receiver and it works fantastically. The remote works from downstairs and down the street (through several brick walls).

So I think I've ruled out any issues with the transmitter.
What could the RF relay device be doing that I'm not?

Would help if you provided some kind of diagram to show how you have wired up the radios.
If you are using the radios with an Arduino, you must use either Virtualwire or Radiohead to process the data
you are sending.

If you'd actually tell us what hardware you have (both transmitter and receiver) and show us your
code, it would a starting point. At the moment I can only guess that you have some sort of problem
with some unnamed module, which isn't going to help!!

You can get a large improvement in range by using the RXB-12 receiver indeed of the super cheap green ones. The cheap transmitters are fine.

But, you still need to do the code right - so you should post the code.

Also, what voltage were you running receiver at?

Normally a poor range is the result of a poor antenna. You can not just cut it to size you have to tune it. One way is with an SWE meter, do you have one?

Grumpy_Mike:
Normally a poor range is the result of a poor antenna. You can not just cut it to size you have to tune it. One way is with an SWE meter, do you have one?

Last month I conducted range tests with 8 different models of receiver and 5 different models of transmitter.

I got the best results (1250' Line-of-sight @ 3.3v on transmitter and receiver) with a simple solid-core wire of about the right length. The spiral springy antennae that some transmitters and/or receivers come with are awful, resulting in less than half the range I got with a simple wire from some old CAT-3 network cable (on both transmitters and receivers, it destroyed range). Even on the ones that came with the spring antenna.

I've been experimenting with dipole antennas, where both the receiver and transmitter connected are at the dipole junction. The antenna terminal is connected to one end of the dipole and the ground is connected to the other. With antennas parallel, I easily get 500 meters range, (open-line-of-sight) with this setup.

The end-to-end length of the antenna was optimized using the program MMANA-GAL and should be 32.8 cm for 434 MHz, using #14 AWG copper wire (1.6 mm in diameter). I've also tried 3-element Yagis, designed using the same program, but there is not a great deal of improvement.

Sorry for not providing more information earlier, currently I’m just testing hardware so I’m using RC-Switch example code with either an arduino sending a signal or using the garage-style remote I mentioned earlier. Either method gives similar results.

Receiver

/*
  Example for receiving

  http://code.google.com/p/rc-switch/

  If you want to visualize a telegram copy the raw data and
  paste it into http://test.sui.li/oszi/
*/

#include <RCSwitch.h>

RCSwitch mySwitch = RCSwitch();

void setup() {
  Serial.begin(9600);
  mySwitch.enableReceive(0);  // Receiver on inerrupt 0 => that is pin #2
}

void loop() {
  if (mySwitch.available()) {
    output(mySwitch.getReceivedValue(), mySwitch.getReceivedBitlength(), mySwitch.getReceivedDelay(), mySwitch.getReceivedRawdata(), mySwitch.getReceivedProtocol());
    mySwitch.resetAvailable();
  }
}

Sender

#include <RCSwitch.h>

RCSwitch mySwitch = RC2Switch();

void setup() {
  // Transmitter is connected to Arduino Pin #10  
  mySwitch.enableTransmit(10);
}

void loop() {
  mySwitch.send("000000000001010100010001");
  delay(1000);  
}

As for the hardware, it appears to be exactly the same as the modules in the photo jermington posted.
I’ll post a photo of the receiver asap.
Both receiver and transmitter are powered with 5v straight from the arduino.

Receiver data pin is connected to pin 2.
Transmitter data is connected to pin 10.

DrAzzy:
about the right length.

Are you using 1/4 wavelength?

jremington:
connected are at the dipole junction.

Sorry I don’t know a whole lot about antennas, when you say dipole junction, are you talking about this? (see attachment)

1.JPG

Yeah, quarter wavelength.

The "dipole junction" is just the space between the two closest ends of the antenna. See the top part of the photo I posted (transmitter and antenna).

Connections to the dipole antenna are labeled "GND" and "ANT" on most modules.

conections to the dipole antenna are labeled "GND" and "ANT" on most modules.

So something connected in these two spots? Looks like that's what you've done in the picture you posted

DrAzzy:
Yeah, quarter wavelength.

That's for each half. In practice it will usually be best if it is very slightly shorter. The impedance of the transmitter and receiver are also important but with these modules is entirely unknown so a bit of experimenting is called for.

Russell.

Don't forget about "desense". Microprocessors generate a lot of RF hash. If you don't keep the wiring tidy, and isolate the microprocessor power supply properly from the receiver supply, it will leak into the receiver and dramatically reduce your working range by introducing a lot of noise.

aarg:
Don't forget about "desense". Microprocessors generate a lot of RF hash. If you don't keep the wiring tidy, and isolate the microprocessor power supply properly from the receiver supply, it will leak into the receiver and dramatically reduce your working range by introducing a lot of noise.

Thanks heaps for that. Turns out my desktop puts out an incredibly noisy supply (too many fans). Tried it on my laptop and it works beautifully even without an antenna!

Yes, the supply rails on a computer are a major source of broadband noise - you have millions of logic
gates switching at MHz and GHz hanging off them!

Pete54321:
Thanks heaps for that. Turns out my desktop puts out an incredibly noisy supply (too many fans). Tried it on my laptop and it works beautifully even without an antenna!

Yes, fans are noisy but they don't produce much, if any, RF noise. That's caused by the fast switching as Mark said.

Russell.

DrAzzy:
The spiral springy antennae that some transmitters and/or receivers come with are awful, resulting in less than half the range I got with a simple wire from some old CAT-3 network cable (on both transmitters and receivers, it destroyed range). Even on the ones that came with the spring antenna.

The length of the wire used for a “helical” (what you call “spiral”) antenna is not the same (not even close) as a quarter wave “whip”. To use helical antennae you need either to have some (very) sophisticated mathematical modelling, or the equipment to test and tune it (as Mike mentions).

The performance of a helical antenna will always be greatly inferior to a quarter wave “whip”. As a first understanding of antenna behaviour, two things are critical, the length - literally you need to catch as big a piece of the signal as possible and similar for transmission - and resonance; being properly tuned.

The simplest way to implement these requirements is as jremington illustrates, to attach a dipole of the correct calculated length directly to the two antenna connections of the module. Note that if you attach only one antenna wire, then you are expecting the random arrangement of your other wiring to act as the other, the “ground plane”, and it is quite unlikely to do this effectively, so even though your “whip” is the correct length, it will be out of tune.

This entirely accounts for the wild variation in performance of these modules as people perceive them.