Increasing the RF 433 Mhz transmitter range

[sanketk]

Hi,

I am trying to design a RF transmitter using the saw resonator for 433 Mhz. I have got it to work but at a very small distance. I am trying to make it work for around 50-60 meters. My circuit is similar to the attachment, but values are somewhat different.

R1 : 50 K , no R2, L2 .
C3: 5pF, C4: 18pF.

I want to increase the transmitting distance, if anyone who can help.

Regards
Sanket

 

[davenn]

Hi there sanket
welcome to the forums

what antenna are you currently using ?
do you need omni-directionality or could you use a directional antenna ... say a 3 element yagi
does it have to be totally portable ?
Is antenna size an issue ?
Is the transmitter able to be modified to add another amplifier stage ?
what is that current transistor ?, what is the output of the transmitter supposed to be ?

answer those questions and then some good suggestions could be given

and you shouldn't omit The L2 inductor

cheers
Dave

 

[sanketk]

Hi davenn

I am trying to build a small remote control, so antenna size is an issue. Currently my inductor acts as an antenna. I cannot modify the transmitter for another amplification stage. The transistor I am using is BFS17A rf transistor.
The output of the transistor is an encoded signal from an encoder IC.
I am trying to build it for small remote control as used in cars so size is an issue.

 

[D.A.(Tony)Stewart]

1st check output power, and supply current. The collector should be twice the supply voltage p-p when On. Can you increase power with battery voltage?

. Then fix coupling cap to antenna with a much smaller value to tune impedance to antenna and resonate at 450MHz. L2 is required for this.

what is the load impedance for Saw filter?