RF antenna Requirements

[tamilarasantpvm]

Hi frnds,
i am using a RF receiver with 434MHz freq. the receiver is enclosed with a hard plastic box. the antenna of the receiver is connected to a 20 cm wire and it is kept out of the box. but my receiver is unable to receive the RF signal from transmitter beyond 50 feet. i need it to be work even at 100ft distance. what can i do. please suggest me the ways to do the same. Thanks in advance...

 

[BradtheRad]

A yagi antenna is a common type, easy to build. It will give you greater sensitivity and some directionality. You probably can get by with just a few elements (parallel wires).

Its size must be designed for the rf frequency. You'll find many articles on building one.

 

[jiripolivka]

A yagi antenna is a common type, easy to build. It will give you greater sensitivity and some directionality. You probably can get by with just a few elements (parallel wires).

Its size must be designed for the rf frequency. You'll find many articles on building one.

In your communication SYSTEM, the range depends on both antennas, transmitter power and receiver sensitivity- rather on the output circuit that triggers when the received signal goes over a limit (maybe adjustable.)
You can use larger-gain antennas like Yagis on both TX and RX, check also antenna polarization. Often the 434 MHz receiver has a tuned inductor that can be adjusted for the best performance.
Check the specifications, the receiver may have a RSSI output allowing to optimize the system.

 

[FvM]

100 ft (30 m) isn't a big distance for a standard 434 MHz link with 10 mW transmitter power. Free space loss over this distance is about 55 dB, gives at least 40-50 dB above receiver noise with simple omnidirectional antennas.

Either you have a transmitter with very low output power, a bad receiver or some other basic problems.

 

[davenn]

100 ft (30 m) isn't a big distance for a standard 434 MHz link with 10 mW transmitter power. Free space loss over this distance is about 55 dB, gives at least 40-50 dB above receiver noise with simple omnidirectional antennas.

completely agree

Hi frnds,
i am using a RF receiver with 434MHz freq..................... the antenna of the receiver is connected to a 20 cm wire and it is kept out of the box.....................

This bit is a problem and very unclear to what you are really doing ??
what antenna ?
What sort of wire ? how about a pic of your setup

you should be using a length of coax say RG58 off the receiver circuit board to the antenna. for the antenna you could use a 1/2 wave dipole ( would be all you need to cover the distance you require) .... a yagi is an overkill

so show us a photo of what you are doing

Dave