Radio Beacon and Reciever

Projects General Guidance
1

Greeting to the Arduino community, while I've played with electronics off and on throughout my life, I just got my first Arduino and love the simplicty and familiarity of the programing language! I never did figure out assembler... :wink:

I am considering a project in which I'd like to build a beacon and a receiver. Problem is I'm not really sure where to start when it comes to antennas and radios. Probably should have taken that HAM Operator course last fall... :wink:

The basic concept is to be able to identify how far away (signal strength) the transmitter is. The receiver can then go into alarm mode if the transmitter wanders too far away. Purposes abound... Kids too far from home, dog ran away, your previous safe just got stolen when the quests left... you get the picture. The distance I was hoping to achieve was upwards of 2 kms (or 1.5 miles) with the ability to reduce that range within software.

Most wireless solutions I've seen are based of some kind of bi directional data communication and this isn't quite what I had in mind. Maybe the transmitter could send an almost morse code at set intervals to identify itself and allow for multiple transmitters but not looking to send "data" as in temperature or device status etc. While the standard "wireless" shields / attachments are based on this data concept, they are also limited in range to around 100-300 meters.

Has anyone seen any projects similar to what I am talking about? If so can you give me a few keywords as I am not having the greatest luck with my searches.

PS I did order some 2.4ghz transceivers even though they have limited range to begin playing with the concept...

Thanks,
Dave

2

I'm not a radio expert by any means, but it seems like the distances you want to achieve could be problematic for the DIYer.

The little I do know is based on higher frequencies, and 1.5 miles at WiFi (2.4GHz) means either extremely high-gain (thus needle-point directional) antennae, and/or high-power radios that need to be licensed.

So, maybe this is more realistic at low frequencies, but even still -- wouldn't you need some elevation to clear obstructions? We can assume one end of the pair (your dog, e.g.) will be at land level. So were you planning on building a tower for the receiver?

3

The basic concept is to be able to identify how far away (signal strength) the transmitter is. The receiver can then go into alarm mode if the transmitter wanders too far away. Purposes abound... Kids too far from home, dog ran away, your previous safe just got stolen when the quests left... you get the picture. The distance I was hoping to achieve was upwards of 2 kms (or 1.5 miles) with the ability to reduce that range within software.

Generally speaking, using signal strength just won't work for what you want to do.

4

Unless all you want to measure is in range or out of range. This distance will vary. You might get 3 different values for distance reliably. Close, Far, and out of range.