RF transmission help required

[aruna1]

Hi
I'm using following RF transmitter and receiver in my final year project. frequency is 434 MHz

Project is about ultrasonic based localization where we use multiple wall mounted ultrasonic receiver systems.

Each Ultrasonic receiver system contains RF transmitter and a RF receiver. SO Ultrasonic receiver systems can communicate with each other.

Transmitter :
**broken link removed**

Receiver:
**broken link removed**

According to data given they should work about 100m.

but my problem is I cant use them to send data reliably more than 2m . Sad Data get corrupted due to lot of noise.(checked with an oscilloscope) if range is more than 2m.

I believe problem is with antennas.

I'm using 30cm long circuit wires for antennas (lambda/2). and I found transmission is possible only if these wires are allowed to hang freely outside the enclosure (plastic). this is a big problem. I need to make a compact system so hanging wires are not an option. It is okey if I can wind the wires and put them in side the enclosure, but if i do so transmission range drops to 20-30cm. Sad

I did some readings and found monopole antennas need large ground planes, which is not available to me. Actually any size of ground plane is not available in the design.

I'm powering up the system with 230AC mains (reduced and regulated using a transformer and 7809/7805).

Transmitter is powered with 9V. (7809) receiver is powered with 5V.

I'm not using any encoder/decoder chip. I'm using PIC12F683 to decode the data.
Data contains 4 start bits + 5 address bits + 11 data bits + 4 end bits.

bit length is 1ms. so transmission speed is 1kbps.

Any idea on how to increase the range up to at least 10m ?

and is there anyway to use single antenna for both transmitter and receiver?
Thank you

EDIT:

Is it possible to get better transmission using following modules? they work in 2.4GHz range and environment I work has a WIFI network.So I believe WIFI network will interfere with these transceivers.

**broken link removed**

**broken link removed**

I'm running out of options, so if above transceiver units will help to solve my problem, I should order them asap. So I'm waiting for your advice.

 

[alec_t]

Elsewhere on the net there are references to λ/4 monopoles being used for 433MHz. Worth a try?

 

[aruna1]

Elsewhere on the net there are references to λ/4 monopoles being used for 433MHz. Worth a try?

I tried but had no luck

 

[crutschow]

I'm not experienced in antenna design, but I believe if you want an antenna shorter than 1/4 wavelength then you need to load the antenna with a proper inductive coil so that it resonates at the transmit frequency. An amateur radio handbook should tell you how to do that.

 

[RCinFLA]

Likely one unit is off frequency. This type of OOK systems are used in garage door openers. Check documentation to see if there is a freq adjustment.