Hi i am new to rf modulation. i want to transmit data via UART mode of 18f452 from one ic to another. maximum range is 100m. please advise me a curcuit to do so. frequency should be below 80mhz and above 10mhz.

Please dont advice to buy a transmitter module as itx not available in my country, also dont tell me to import because the module would not cost me as much as the importing duty and other stuff might cost me....
do help me... my whole project depends on it!!

also do advise a receiver circuit with it...

Thanks in advance!!

 

Anyone?? hello???

 

if no one can help with that... then tell me if i can connect an fm transmitter to the PIC to transmit dtmf tones... if yes... den how??

 

Hello,

You probably can make some transmitter - reciever couple in one of the free ISM bands:
http://en.wikipedia.org/wiki/ISM_band

For information on RF techniques you can have a look at my RF related links

Bertus

 

Thanks for the reply....
i would like to make a transmitter on 6MHz and its receiver... the ques is how??
please advice a circuit diagram...

waiting for your reply!!

 

Hello,

You probably can make some transmitter - reciever couple in one of the free ISM bands:
http://en.wikipedia.org/wiki/ISM_band

For information on RF techniques you can have a look at my RF related links

Bertus

hey i found this circuit http://www.circuitdiagram.org/27_mhz_transmitter.html which seems quite easy... i want to replace the mic with PIC out..... can u help on dat??

 

Hello,

What will be the transmission speed of the digital data?
You will need to convert the digital data to some FSK signal.
This page of the EDUCYPEDIA will give you information on digital modulation techniques:
http://www.educypedia.be/electronics/rfdigmod.htm

Bertus

 

i have set the UART of the PIC to operate at 2400bps.

 

thanks for the link... bt i cannot understand anything!

 

btw... are u telling me bout DTMF way??
it would be great if there is an answer is for my first question...

 

ok... i would now like to change the question as i have found an encoder decoder IC available in my country...
now i want the transmitter module schematic not of an ISM band bt of an fm band... itx not a crime here as i want to transmit in my home only dat can be around 50m max... it should be 5V power supply as my whole system is built on 5v power supply... do reply!! Waiting!!

 

Please dont advice to buy a transmitter module as itx not available in my country, also dont tell me to import because the module would not cost me as much as the importing duty and other stuff might cost me....
do help me...

HF circuits are not easy to deal with, especially with the layout considerations. Which country are you living in? 27MHz toy car receivers/transmitters should be easily available anywhere, don't they?

Have a look at this site:http://radio-control-schematics.blogspot.com/2007/05/27mhz-toy-car-transmitterreceiver.html

 

Hi... I posted somthing and it magically disappeared...
Anyway... I have found a decoder encoder available in my country...Now all I need is a tx/rx circuit... Fm circuit is quite easy make nd its receiver too... mow please tell me it it can b done... Dont worry bout the law.. as transmitting till 100m is not a crime here... and i want to transmit in a home with a max range of 50 meters.. advice me a circuit... and one more thing... it should be working on 5V as my whole project is working on 5V... Waiting for your reply...

 

HF circuits are not easy to deal with, especially with the layout considerations. Which country are you living in? 27MHz toy car receivers/transmitters should be easily available anywhere, don't they?

Have a look at this site:http://radio-control-schematics.blogspot.com/2007/05/27mhz-toy-car-transmitterreceiver.html

they are but the are expensive too...
though i'll check it...

 

HF circuits are not easy to deal with, especially with the layout considerations. Which country are you living in? 27MHz toy car receivers/transmitters should be easily available anywhere, don't they?

Have a look at this site:http://radio-control-schematics.blogspot.com/2007/05/27mhz-toy-car-transmitterreceiver.html

i have seen it earlier and i dont understand where the data input will be...
and i want a circuit working on 5V...
Thanks!!

 

i have seen it earlier and i dont understand where the data input will be...
and i want a circuit working on 5V...
Thanks!!

Well, you'll have to experiment a bit. I'm quite sure the circuits can be adjusted to work at 5V as well.

A modulation of the transmitter could be achieved adding/replacing the 15p cap with a variable capacitance diode. At the collector of the second transistor in your receiver you should then be able to retrieve your signal, but it will need further treatment.

Sorry, I know you want a readymade design, but I guess u have to do some experiments.

 

Quote:
Originally Posted by ssm14293
i have seen it earlier and i dont understand where the data input will be...
and i want a circuit working on 5V...
Thanks!!


Well, you'll have to experiment a bit. I'm quite sure the circuits can be adjusted to work at 5V as well.

A modulation of the transmitter could be achieved adding/replacing the 15p cap with a variable capacitance diode. At the collector of the second transistor in your receiver you should then be able to retrieve your signal, but it will need further treatment.

Sorry, I know you want a readymade design, but I guess u have to do some experiments.

thanks man.... but i m not good at this.... can i use an fm band to transmit signal of an encoder?? i have an fm transmitter with a mic, can it be used for this purpose... it does not transmit more than 15m bt that will still work for me.

 

thanks man.... but i m not good at this.... can i use an fm band to transmit signal of an encoder?? i have an fm transmitter with a mic, can it be used for this purpose... it does not transmit more than 15m bt that will still work for me.

Might be worth trying. Do you have schematic of this transmitter?

 

Might be worth trying. Do you have schematic of this transmitter?

unfortunately... no... itx a single transistor transmitter... i'll buy it and let you know... doesnt cost much... compared to what i hv invested in this project... :/
is it possible though??

 

I'm more worried about it's frequency stability and not if it's possible to modulate it/adapt to yor needs. There is something else too. You won't have any feedback if you use only one transmitter, did you think about that? Or does it not matter if you loose a bit once in a while?
The sending MC will have no information about what the other MC received...