Are There Better Antennas for Tx433/RX433 RF Modules?

[digitalblggr]

HI,

I am using tx433/Rx433 RF modules to transfer some data between two AVRs. I know that we have to use 30-35 cm simple wires as antennas.

I send out out two bytes. The second byte is the actual data , and first byte is to get rid of unwanted information. However, I have a hard time receiving the signal, and have to send it out a bunch of times. I noticed if I play with wires(antennas) for e.g.when I get receiver antenna really close to transmitter I receive data much faster. This made me think maybe there is a better choice for antennas out there.

Any suggestions?

P.S. I am supplying 9V to Tx433..so I should at least get ~200feet according to the datasheet, but so far I can't go beyond few cms.

 

[vk6kro]

A quarter wave length at 433 MHz is 17.3 cm, so this is what you would use for a simple antenna. It should actually be a little shorter than this.

You can use a dipole which is a half wavelength (34 cm) fed in the middle by a short feedline.

Or, you could use a Yagi antenna which consists of a dipole (32.3 cm) fed as before with a reflector (34.6 cm) 5 cm behind it and a director (30.6 cm) 13 cm in front of it.

You can get calculation programs for designing Yagi antennas by searching on Google.
One of these is this one:
http://www.vk5dj.com/yagi.html

You can make a simple test antenna by connecting a half wave voltage doubler to the centre of a dipole and measuring the output of the voltage doubler using a multimeter on a low current range.
The voltage doubler should have Schottky diodes like the BAT85 in it. The capacitors should be about 1000 pF but cut to have very short leads.

In this diagram, above, you would omit the transformer and connect the two ends of the dipole feedpoint to the input of the doubler.

With this tester, you could adjust the transmit antenna for maximum received signal into the tester. You do this by adjusting the spacing between the elements of the Yagi.

Then you could make a similar one for the receiver and test it by attaching it to the transmitter.

Using better antennas should give you more reliable results and teach you a lot about antennas.