433Mhz transmitter/receiver for Arduino to Arduino communication (1km range)?

Projects General Guidance
1

Hi, as part of a university project I'm trying to connect two Arduinos together via rf to share some data. One Arduino (Uno) will be connected to a sensor and transmit sensory readings to the other Arduino which has a wired internet connection so that the data can be uploaded to the web.

I've been trying to find transmitters/receivers that fit my problem (433MHz, ~1km range) but I'm having real trouble with it. Are there any well known transmitters/receivers for this purpose and whereabouts could I find them available in the UK?

This is my first Arduino project and I'm pretty inexperienced with this type of practical electronics. Any advice would be appreciated. GSM/Bluetooth are not options as the context of this task is relating to rural areas with no phone reception.

Thanks!

2

You can easily buy high power 433 Mhz transmitters e.g. on eBay, but I suspect than none of them are legal in the UK.

(Unless you have a ham radio license)

3

rogerClark:
You can easily buy high power 433 Mhz transmitters e.g. on eBay, but I suspect than one of them are legal in the UK.

(Unless you have a ham radio license)

I can find loads of short range ones like this on eBay:
http://www.ebay.co.uk/itm/433MHz-315MHz-DC5V-ASK-OOK-RF-WIRELESS-TRANSMITTER-RECEIVER-MODULE-ARDUINO-UK-/221297956541?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item338662d6bd

It's finding ones with antenna slots for longer range that is proving to be a bit harder for me. Unless I'm missing something and those cheap ones can be altered to fit my needs?

4

but I suspect than one of them are legal in the UK.

I suspect you meant to say "none of them are legal in the U.K."

5

I can find loads of short range ones like this on eBay:

I have some of those. The work fine for short range.

6

Thanks @raschemmel

Corrected my typo !

I recall there is another very long thread (last week) about the legality of various 433Mhz Tx units.

There are limits to ERP etc on ISM bands (well there are limits on practically any band, depending on what license you have to operate on those bands)

I did find this Transciever on eBay http://www.ebay.co.uk/itm/433Mhz-Wireless-Serial-Transceiver-Module-1km-/221445766409?pt=UK_Computing_Other_Computing_Networking&hash=item338f323d09

But its probably not legal in the UK, and I'd not trust the specs given on eBay, they are usually wildly exaggerated !

7

The range of 433 Mhz transmitters is heavily dependant on the terrain between the Transmitter and Receiver, and how much obstruction there is.
Most of the information related to range assumes line of sight conditions , ie nothing in the way .
Going to higher power helps a bit , but not much if the terrain is obstructed.

8

@Hooby

You could take a look at some of the Radio Control related stuff e.g. on HobbyKing

e.g.

And also look at other bands.

including the 5.8Ghz video link stuff and also 2.4Ghz

Though normally, the higher the frequency the less range you will get (but some of the video link stuff outputs a lot of power :wink:

BTW. @mauried is totally right. Terrain will play a big part in this, especially as you use higher frequencies.

You should also look at yagi style antennas for 433mhz (you could mount the whole TX unit on the antenna)

9

Any power restrictions at the 'remote' end? Apparently you can get WiFi over a kilometer with clear line of sight and directional antennae. Alternatively some of the Ciseco RFRu transceivers claim to have a range of over a kilometer, although I'm sure that would be heavily dependent on the environment.

10

I've been trying to find transmitters/receivers that fit my problem (433MHz, ~1km range) but I'm having real trouble with it.

Natures warning sign, if others aren't already using a similar setup, then there is probably a reason.

11

Here's some links on how to build the Cloverleaf and Skew Planar antennas...

FYI, if you are NOT using one of the exotic antennas in the above links then your Tx antenna should be about 20 cm COILED on a fat ball point pen or something thicker than a pencil (like a AA battery) and your Rx antenna should be about 17 cm STRAIGHT solid copper wire ,
(about 20 - 22 guage) insulated.

12

From what I recall, having a high gain antenna would technically make most of these transmitters illegal.
Because the regulations specify things like field strength, so making a better antenna will focus the power and give a high field strength in one direction, and make them illegal.

See this thread

http://forum.arduino.cc/index.php?topic=246253.0

However as a counter point to this.. I suspect there are loads of illegal devices already in use in the UK (and the rest of the world), because people have not worried about whether what they are doing is strictly legal or not.

i.e Loads of people will have bought (from the Internet) all sorts of technically unapproved items which have transmitters in them e,g, "baby monitors", external thermometers, wireless operated garage doors etc etc. Many of which would probably fail CE certification ;0)

13

I won't tell if you don't...

14

If you are not required to use 433 MHz radios, the XBee Pro 2.4 GHz 60 mW radio yields line of sight ranges of over 1.5 km. Series 1 is the easiest to use. I don't know whether they are legal in the UK, though. XBee Pro 60mW Wire Antenna - Series 1 (802.15.4) - WRL-08742 - SparkFun Electronics