Author Topic: Inair4 + arduino + radiohead library  (Read 1050 times)

saramirez

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Inair4 + arduino + radiohead library
« on: January 04, 2016, 11:40:09 AM »
I've been trying to use the iair4 modules with an arduino for long distance telemetry, and haven't been getting long distances (i expected about 2 km). I recently did some tests using an updated version of the RadioHead library, with the RH_RF95 class that has been modify by it's author to support theese modules, and i got some good results.

I used two arduino Pro (3.3V), each connected to a inair4 module as it's instructed on the radiohead page (http://www.airspayce.com/mikem/arduino/RadioHead/classRH__RF95.html). One is loaded with the rf95_client and the other with the rf95_server examples provided. I used Bw = 31.25 kHz, Cr = 4/8, Sf = 512chips/symbol, CRC on, and used a transmitter power of +14 dBm.

I was also testing the Moteino LR, which uses a different chip but is compatible with the same library. The setup is the same, but the power is set to +23 dBm.

First, i did a LOS test. I placed a module with the client example and drove off in a straight street until i lost signal. I actually did not loose signal but ran out of street, and i got to about 2.7 kM, both with the inair4 and the moteino.

I then did a test with obstacules. I placed a module in my house, in my room, and drove off. There were multiple buildings, houses, trees in between the two nodes. They were at different altitudes as well.

With the moteino i got to about 500 mts.

With the iair4 i got to 1.2 kM using a Whip 1/4 wave antenna (http://modtronix.com/ant-ra57-433.html) and to about 1.7 kM using a dofferent monopole antenna.

What i observed is that while the inair4 allows much less transmitt power it has a much better sensibility (i meassured a RSSI  down to -103, while with the moteino it stopped at about -80).

I did one more test in which a left a moteino in my house and use a inair4 to pick up the signal. I got to about 3.3 kM, though this would only be a one way com, because the moteino is not sensible enough to pick up the signal, nor the inair4 powerfull enough to work in the other direction.

Greetings!