Radio Communications: Proper Guide for Newbies?

[lpry]

Hi all,

I've run into a rut with the project with how one uses a Pi to communicate via radio. I don't want to fork out the money for the PITS board, so I've been looking at Radiometrix modules but I can't figure out how to use the Pi to send and receive data over radio. Can somebody post a guide on how to do this?

Thanks a lot.

[daveake]

Well, the PITS software and hardware are all open-source so you can refer to those.

The circuitry needed is shown here - https://ukhas.org.uk/guides:linkingarduinotontx2, however don't try and use that software method on a Pi, as it relies on accurate timing; instead use the serial port and send data to that.

Dave

[jwl]

You might want to consider using the APRS protocol for your tracking needs. APRS is commonly used for high altitude balloon tracking. It is generally used on the ham radio frequencies but could be used with other types of radios.

It is implemented in numerous commercial products, kits, and open source software. There is a global network of gateway stations that receive signals over the radio and forward them to servers over the Internet. You can see the results at http://www.findu.com/ or https://aprs.fi/

For more details, Google for APRS high altitude balloon.

Open source software is available so the Raspberry Pi can be used a tracker, receive decoder, and an Internet Gateway station.
As an example, https://github.com/wb2osz/direwolf/blob ... /README.md

[daveake]

APRS stations might exist globally, but not every country allows the use of amateur radio from an airborne device, so in those countries (e.g. UK) it's not legal to use APRS frequencies from a balloon.

Personally, even if I was in a country where airborne APRS is viable, I'd prefer to fly ISM (e.g. RTTY or LoRa) where I can have more frequent position updates and have the option of also transmitting images over the same radio link; however APRS would then have the advantage of an existing receiver network.

Dave

[OutsourcedGuru]

High-altitude ballooning with a Raspi is definitely on my to-do list. For communications, I would likely use LoRa for that.

https://www.cooking-hacks.com/blog/send ... l-galileo/

The LOS (line of sight) has about a 13.4 mile range and the NLOS is more like 1.2 miles.

If not LoRA, I would attempt to use cellular, I'd guess.

I would attempt to periodically broadcast the GPS coordinates as well as to log them for later retrieval.

[daveake]

LoRa range depends on power, bandwidth and other settings. For UK airborne use on the 434MHz bands, we're limited to 10mW and the LoRa 20.8kHz bandwidth setting. Range with those settings from a balloon at high altitude is hundreds of miles, comfortably. I think the record with RTTY at 10mW is about 500 miles and LoRa has a slightly better range. Basically, if you have LOS to the balloon then LoRa should work.

As you mention "cellular" I'm guessing you're in the USA, in which case 434MHz needs a ham licence but 915MHz does not. LoRa modules are available for 434, 868 and 915MHz bands. I don't know what the power/bandwidth limitations are for 915MHz in the USA but other things being equal 915 has less range than 434. I'd still expect it to perform very well though.

Cellular is next to useless as a primary tracker; possibly useful as a backup.

Dave

[cpunk]

Not sure if it's legal in the country you reside in (it has 33dBm of RF output), but I'm using the E31-TTL-2W from CDE for more than just hobby projects, but also industrial telemetry and a prototype environmental monitoring mesh. It's a narrow band radio modem with adjustable frequency channels. No frequency hopping or fancy stuff.

http://www.cdebyte.com/en/product-view-news.aspx?id=129

(however, they are a bit on the heavy side for a balloon)

[IotBitOfficial]

Have You had a look at our products? We provide HAT's for Raspberry Pi's which give them mobile communication features such as 4G 3G and GSM. We also provide a Gas sensing Hat which has the capability to measure temperature and humidity. check it out @ altitude.tech