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Please do keep in mind that I have no background in electronic communication. The idea is to receive data from electronics at long distances.

The distance I will be looking at to read data from electronics is around 10 km (6 miles) and possibly at a later stage longer distances and I would like to keep cost as low as possible.

The route that seems to be low cost is getting a raspberry pi zero, connect the electronic device to it and then transmit the data received from the device over radio.

The user will have a app on his or her phone/device which will receive these radio signals and then decode it into an app which the user in return can understand.

The problem, if I am not mistaken, with this route is security won't be that great as anybody with the same frequency will be able to receive the data and also, again if not mistaken, it is illegal the transmit radio signals over great distances.

The questions I have is

  • Is this theory even possible ?
  • Is there a better way of achieving this goal ?
  • What topics do I have to research to understand how electronic devices can communicate with a pie as well as sending and receiving radio signals and decoding it ?

A simple example is that if a switch is flipped on or off the pi is notified the signal is broadcasted the user's phone receives it and then the user is notified through his or her phone.

EDITED I see a lot of people mention GSM but this uses a cellular network, sadly this option won't suffice as there is no cellular network in the area the pi will be used.

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    \$\begingroup\$ it is illegal the transmit radio signals over great distances. Not persé, it depends on the country you're in, you might need a license and the frequency band you're using. Short wave communications is a hobby for some people and links can be setup spanning the globe. \$\endgroup\$ – Bimpelrekkie Oct 17 '17 at 12:27
  • \$\begingroup\$ @Bimpelrekkie Thank you for informing me, I fixed it. \$\endgroup\$ – Sand Man Oct 17 '17 at 12:33
  • \$\begingroup\$ You've mentioned smart phones and tablets. They can receive (or call up) data over the internet. All you need on the remote side is a GSM modem that dumps the data to a place on the internet that the smart phone app can access. \$\endgroup\$ – JRE Oct 17 '17 at 12:44
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    \$\begingroup\$ How much bandwidth? 1 byte per hour, or 10 Mbps? Also do you have no cellphone coverage at all, or "just a tiny bit" ? \$\endgroup\$ – peufeu Oct 17 '17 at 15:07
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    \$\begingroup\$ You might be able to stay below some legal limits by using spread spectrum communications. In fact, it's possible to stay completely under (less than 1:1) the ambient noise levels using it. For a time in the US, this was legal. It's not, anymore, as they've reserved a couple of the really useful techniques to the military here, now. So you are forced to go "above the noise" or else face some serious problems. But in your location, depending on laws, you might consider it. \$\endgroup\$ – jonk Oct 17 '17 at 17:27
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If you do not want to customize hardware on the smartphone side your choices are limited to, largest range on top:

  • Iridium network. (satellite internet)
  • LoraWAN. (long range 433 Mhz Internet of Things)
  • Text messages.
  • Cellular internet.
  • WiFi.

If you do want to create custom hardware on the smartphone side, you could see if any of the amateur radio bands suffice, or possible the semi-unlicensed 400/800 MHz ISM bands.

Or maybe microwave beam connections. Like Mikrotik RBLHG or Ubiquity.

Your question right now is quite broad and does not show much research. Maybe start googling with the above.

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    \$\begingroup\$ Your list should include microwave point to point. Depending on geography, 6 miles might require an intermediate repeater. \$\endgroup\$ – R Drast Oct 17 '17 at 13:33
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You could try Zigbee. It has range up to 10km. It also appears to run in the licence-free band in many countries.

XBee and ZigBee for long distance signal transmission

https://ham.stackexchange.com/questions/3729/do-you-need-a-radio-licence-to-use-zigbee-xbee

If you need to go further later, I'd suggest you setup repeater units.

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Not sure if this counts as a full answer, but definitely if you're in a (even slightly) developed area, what you want is a GSM modem. At the level you're currently at, you certainly don't want to be dealing with any low level radio design, and you also don't want to deal with protocol design.

If you use a GSM module like this, you just plug it into your pi and you can start sending and receiving text messages. Assuming you're not dealing with any ultra low power stuff (and even then, this is still pretty good for sending), this is definitely one of your best bets.

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  • \$\begingroup\$ If you want to send a lot of data, you can also use a 3G/4G modem (as @JRE suggests) \$\endgroup\$ – BeB00 Oct 17 '17 at 12:45
  • \$\begingroup\$ The problem with this approach is that the place I want to use this is on a farm with little to no cellphone signal. \$\endgroup\$ – Sand Man Oct 17 '17 at 12:46
  • \$\begingroup\$ That is unfortunate, does it have wifi? Satellite internet is pretty expensive, and the other alternatives are typically not quite as easy to set up and use \$\endgroup\$ – BeB00 Oct 17 '17 at 12:50
  • \$\begingroup\$ Well I don't have a problem educating my self. I never expected this to be easy. I just need someone to point me in the right direction into what to research \$\endgroup\$ – Sand Man Oct 17 '17 at 13:01
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I want to use this is on a farm with little to no cellphone signal

There is a difference between "little" and "no" signal.

There's a way, it is very "ghetto" but you can put the GSM module on a parabolic dish and point it in the direction of the nearest cellphone tower.

If you have direct line of sight between the two endpoints of your "link" you could even use two parabolic dishes and WiFi.

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  • \$\begingroup\$ This is what I call thinking outside the box. Thank you for the suggestion. \$\endgroup\$ – Sand Man Oct 18 '17 at 5:25

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