Have I worked it out?

[tim_l_012]

Hi All,

I am very interested in RF remote control, and I have done quite a bit of research over the last few days. I have gone out an purchased a cheap remote transmitter and receiver, that works for up to 45m.. but the only problem is its a doorbell

I basically want to learn about how RF transmissions work, I found a diagram on the net called Simplest RF transmitter, and I couldn't work out what the coil bit was.. so if someone could explain that to me that would be excellent.

Also, how do you work out what frequency you are transmitting? And how do you configure the receiver to that frequency.

I know its a lot of questions but this stuff has me really interested

Thanks in advance,

Tim.

 

[k7elp60]

Have I worked it out

A simple answer to your question is tuned circuits. Both the transmitter and the the receiver require a tuned circuit of some form. An inductor and a capacitor.
When you are changing stations on a broadcast receiver you are adjusting the frequency of one or more tuned or resonate circuits. For exact and stable frequencies whether it be for receive or transmit there is bound to be a quartz crystal somewhere in the frequency determining circuitry of either unit. The quartz crystal is a form of a resonate circuit, only it is highly accurate and very stable, where as regular tuned or resonate circuits are not as accurate or stable.

 

[ElectricWraith]

Tim,
Can you post a schematic if you have one? I'm too lazy to google it.