433MHz transmitter

[missy]

hello,

i need to know all thing about 433MHz transmitter that sold in market..can u list the terms of it,how it function,the opereration in transmitting data etc..

tQ

 

[Russlk]

Your question is too general, what do you want to do?

 

[missy]

transmitter and receiver 433MHz

hello,
actually i need to know the characteristic of 433MHz transmitter..is this transmitter can transmit data within long distance,it's about 5km?if not/yes, why not/yes?
ok, tQ

 

[Russlk]

If you can see the receiving antenna it might work but at 433MHZ, transmission is "line of sight". I don't know the law in Malaysia but the power needed to transmit 5km is probably illegal. You can buy 100mW transmitters inexpensivly but would need parabolic antennas on both ends to transmit that distance.

 

[boncker]

There is chips that transmit in 433 MHz, used in car alarms and automatic doors, for example.
I'm not sure the model of this chip but is not difficult to find the datasheet on the internet and it will help you.

Good luck.

 

[DigiTan]

They have 433MHz ASk-AM modules at Reynolds Electronics; and smaller surface-mount modules at Linx Technologies.

 

[Russlk]

www.qkits.com is another source of 433 mHz transmitters.

 

[missy]

antenna

hello..i need to know the different betwn half wave dipole antenna and quarter wave dipole antenna...
if i want to design that antenna, are just simply use a wired (assume that is the antenna) ?
what criteria that we consider when design the antenna?

 

[Russlk]

A quarter wave dipole is a single wire 1/4 wavelength long that can be end fed from a 75 ohm source (50 ohms works also). The length of the 1/4 wave antenna can be calculated from: Length (inches)=2952.5*K/F
where K is a factor depending on the size of the wire and F is the frequency in mHz. You may be able to find a chart of the K factor with a Google search; if not, use 0.96.

The 1/2 wave dipole consists of two 1/4 wave dipoles fed with a 150 ohm source. If you can get some TV twin lead, you can make a folded dipole having 300 ohms impedance. Do a Google search for folded dipole.

 

[missy]

encoder and decoder

hello,,
what characteristic will we consider when we use the encoder and decoder for the circuit..
actually what is the encoder and decoder function?
tQ

 

[Russlk]

If you send raw digital data, there is no way to know what part of the data you are receiving, therefore you need a system of coding. Also, if there is no clock, data recovery will be difficult. Look up Manchester coding, that is a way to send a clock with the data. Other coding you will have to work out yourself.

 

[DirtyLude]

http://www.rhyshaden.com/encoding.htm

I thought Manchester encoding was more for DC balance, than clocking. My transmitter module requires it, or it loses 'tuning'. I guess you could use it to sync clocks, though, I never thought of it that way.

 

[DigiTan]

Re: encoder and decoder

hello,,
what characteristic will we consider when we use the encoder and decoder for the circuit..
actually what is the encoder and decoder function?
tQ

If you use a microcontroller, you can usually forego the store-bought encoders and program your own. To echo Russlk and DirtyLude, Manchester is sort of the Swiss Army knife of digital encoding. It provides its own clocking, dc balance, and travels through DC-intolerant media (like a 433MHz IC).

The downside is it takes twice as long to transmit 1 bit--since each bit requires both high and low bit halves. Because of that, your bitrate is reduced to half, so a 9600bps model becomes 4800 and so on.

 

[Nigel Goodwin]

For more details of Manchester coding, and the reasons for using it with an RF link, check my PIC tutorial!.