Radio transmitter

[Javier Manzano]

Hi guys!

I'm doing some research on a new project I want to do this Xmas. I was looking forward to developing a radio transmitter and, if it's possible, recieve the signals from my car.

The issue is I'm not sure which would be the best approach. On the one hand I've seen with a Raspberri Pi it wouldn't be too difficult, but maybe doing the whole circuit design myself would be more fun. In any case, I had several doubts:

• FM or AM? What's the practical difference for what I want to achieve?
• I know there are some frequencies that are restricted, is it possible to transmit in a permitted one and sync with the car's radio?
• What modules should I look to design?

As I said, I'm not sure how to start with this, so hopefully you guys can help me a bit with the design!
Thanks a ton!

 

[Arouse1973]

Hello
You can transmit on 433 MHz band and 2.54 GHz and 5.8GHz and 24.125 GHz, there are others. Your best bet is to look for a cheap 433 MHz TX and RX. I have found AM to be better for this sort of thing. Have a look at your local electronics suppliers and see what they have.
Adam

 

[davenn]

look for a cheap 433 MHz TX and RX.

if he goes for one of these standard products as you suggested
modulation type is already set and doesn't need to be thought about

 

[Javier Manzano]

What's the difference on transmitting in lower frequencies from higher ones?

Since I was looking forward to doing myself the whole circuit, instead of buying the transmitter already built, a kind of AM transmitter I found was this:

What are the "modules" within this circuit, as in, what do the different parts do? I was hoping to understand the reasons behind it.

The thing is I would like to transmit within a distance of several kilometers, if that is possible and recieve the signal as "listenable" as possible.

 

[Arouse1973]

Hi You have to be careful doing your own circuit. It will have to comply with a standard to make sure you are not transmitting out of band and that the RF power isn't greater than is allowed by the ISM band you choose. I personally would buy an off the shelf module.
Adam

 

[Javier Manzano]

Well, certainly that is another possibility. The third one is to use my raspberry. I found this really sexy project (here) that uses python and C to turn the pi into a pretty powerful transmitter.

One of the things I look forward to if this projects gets somewhere this Christmas is to implement a better version, along with a receiver, to take with me when I go hiking to the mountains with my friends and maybe cover a range of 1-2km. Maybe it's not even viable. I'm doing my research

 

[davenn]

The thing is I would like to transmit within a distance of several kilometers, if that is possible and recieve the signal as "listenable" as possible.

then you will need a higher power transmitter and it will need to be tested for type approval and licenced
this will cost you lots of money.
If you decide not to get the testing done by an approved testing company, then get it licenced
and just put you product on the air then you leave yourself open to prosecution, which could cost you
everything you own, when you start interfering with legal transmitter / receiver systems

One of the things I look forward to if this projects gets somewhere this Christmas is to implement a better version, along with a receiver, to take with me when I go hiking to the mountains with my friends and maybe cover a range of 1-2km. Maybe it's not even viable. I'm doing my research

Do it properly and legally
use citizens band (CB) radio ( or what ever it's called in Spain or learn for your amateur radio licence
with which you can then build your own gear legally


Dave

 

[Javier Manzano]

And could I do all that in the CB?

 

[davenn]

CB is designed for voice only communications

if you are wanting to transmit data over a link, then you are back to a specialist system

 

[Javier Manzano]

CB is designed for voice only communications

if you are wanting to transmit data over a link, then you are back to a specialist system

Gotcha. Looks like I'll have to be stay happy with a small Tx/Rx to play around at home hahaha