# Help needed Radio data transmission

#### jxyl

Joined Mar 21, 2006
2
Hi guys:
I'm doing a project on radio data transmission. Stuck on some calculation stuff, hope you guys can help.
Just bit of background info on the project. I suppose to send Digital Data via AM frequency (between 500KHz to 1500 KHz). It is done by modulating the digital data on to a carrier signal, or Amplitude Shift Keying. A class C amplifier is used to do this and the modulation is amplified onto a LC tank circuit which resonate with the carrier frequency and sends it out.
I've done quite a lot of research on the thing, and now starting on the calculation for all the capacitor and resistors. Just need some hint or maybe some sample working out. and what sort of diode to be used on it. And what should i use to produce data input in this case (just a stream or one-by-one of 1 and 0 is good enough). I've attached a simple drawing of the circuit i came up (please excuse the drawing), not sure if its right, please correct me.
[attachmentid=1294]
Also i need some IC with RF amp, detector and AF amplifer for my receiver, where can i find them because i was told it's possible to find such IC.

Any help would be greatly appreciated

Cheers

#### Papabravo

Joined Feb 24, 2006
15,537
Originally posted by jxyl@Mar 21 2006, 07:11 AM
Hi guys:
I'm doing a project on radio data transmission. Stuck on some calculation stuff, hope you guys can help.
Just bit of background info on the project. I suppose to send Digital Data via AM frequency (between 500KHz to 1500 KHz). It is done by modulating the digital data on to a carrier signal, or Amplitude Shift Keying. A class C amplifier is used to do this and the modulation is amplified onto a LC tank circuit which resonate with the carrier frequency and sends it out.
I've done quite a lot of research on the thing, and now starting on the calculation for all the capacitor and resistors. Just need some hint or maybe some sample working out. and what sort of diode to be used on it. And what should i use to produce data input in this case (just a stream or one-by-one of 1 and 0 is good enough). I've attached a simple drawing of the circuit i came up (please excuse the drawing), not sure if its right, please correct me.
[attachmentid=1294]
Also i need some IC with RF amp, detector and AF amplifer for my receiver, where can i find them because i was told it's possible to find such IC.

Any help would be greatly appreciated

Cheers
[post=15251]Quoted post[/post]​
I don't know what part of the world you live in, but what you are proposing would be clearly illegal in the United States, since that frequency range is reserved for AM broadcasting.

Would getting an Amateur Radio Licesnse and using RTTY or PSK31 be too much trouble for you?

#### thingmaker3

Joined May 16, 2005
5,084
This is what PapaBravo is talking about: http://www.ntia.doc.gov/osmhome/allochrt.pdf

I don't know about enforcement abroad, but the American FCC does not have a sense of humor.

European list is here: link- note that it does not allocate frequencies below 925 MHz. Is this because individual nations rule those?

Picking components and component values is an iterative process. I like to start with what I have on hand (if I have something on hand that will work). Failing that, one could choose a transistor first. Eb and Ec would easily be determined by the transistor's needs. Eb and the carrier frequency would yield a value for the coupling cap.

Input data can come from one of your PC's ports.

For your reciever, try Froogle or eBay.

#### karthikv

Joined Jun 29, 2008
1
The chip you need is the MK484
Ya btw i am doing the same thing as you i want to know as to how you did the circuit can u pass me the circuit diagram with some explanation if possible my email id is maths.karthik@gmail.com

#### SgtWookie

Joined Jul 17, 2007
22,221
The ZN414 is a later copy of the original MK484.

You can build receivers with them all day. It's the transmitters that will get you in a great deal of trouble.