Hi, I am searching for a wireless component that allows me to send 192 bits per second one-way over a distance of up to 2 KM (About 1.3 miles) preferably even more.
Most systems that can transmit over this distance all need an antenna. I don’t really wand a big antenna. I am building a system where aerodynamics are very important and because of this the amount of drag created by the antenna needs to be as small as possible.
Price isn’t really a big issue but the size is, and even more important is the range.
So my question is:
What kind of RF / wireless communication components are there available?
And what are the guaranteed operating ranges outdoor?
And are they approved to be used in Europe?
Basically what are your recommendations?
If you can’t afford a good enough antenna on the aircraft, you can always compensate with a directional antenna on the ground. With a 2.4 GHz 50 mW XBee on both sides, one with a rubber duck dipole antenna (air) and one with a patch antenna (10 dBi or better) should talk reliably at those 2 km assuming line of sight is maintained. Even 5 km would work with this config.
Link budget:
Transmit: +17 dBm (50 mW)
Dipole antenna: +5 dBi
Losses in cables etc.: -3 dB
Free path loss @2 km: -106 dB
Ground patch antenna: +10 dBi
Losses in cables etc.: -3 dB
Total power at receiver: -80 dBm
The XBee receiver claims sensitivity of -100 dBm, that would give you 20 dB of margin. Assuming a more realistic sensitivity of -90 dBm you still get 10 dB margin, which is more than enough for a good link.
I think it would work okay even with two dipoles, big ones (5 dBi and more).
Edit: No problem in Europe. Data rates should be in the 50 kbit/s range.
ingmarHendriks:
Hi, I am searching for a wireless component that allows me to send 192 bits per second one-way over a distance of up to 2 KM (About 1.3 miles) preferably even more.
Most systems that can transmit over this distance all need an antenna. I don’t really wand a big antenna. I am building a system where aerodynamics are very important and because of this the amount of drag created by the antenna needs to be as small as possible.
Price isn’t really a big issue but the size is, and even more important is the range.
So my question is:
What kind of RF / wireless communication components are there available?
And what are the guaranteed operating ranges outdoor?
And are they approved to be used in Europe?
Basically what are your recommendations?
802.15.4 on 900 or 868 MHz, with 50mW or so, will likely do that. For several miles, you'll need more like 500mW or so. Digi and others have such radios but the get up to and beyond $100 and use a lot of battery power when they aren't sleeping.
Yes, do a link budget. In line of sight, it can be accurate to about 3-5 dB. Assure you have 8-16dB of margin.
You can check the datasheet of the module before buying them. That will help you gaining more knowledge about the range and other information about the module. Based on that you can choose one suitable for your requirement.
I know the Xbee pro series1 will go over a mile with the rubber duck on the TX side and a patch on the Rx. Only a mile because I ran out of land. I was getting approximately 35 degrees left and right and was still pulling good signal.
2Km, low rates… I’d use 868MHz in the EU, same products we use in the US in the 902-928 band. Lower freq = longer range.
There are some 868/902 XBee format. Use something with at least 50mW. Higher bit rate = shorter transmitter-on times = longer battery life.