- Published: Tuesday, 19 March 2013 18:47
- Written by Ravi Pujar
I was looking for a RF transceiver with good RF range for using in my project. But, when i looked at the specifications of the wireless devices, i did not find the RF range or distance mentioned in the details. This article is to give an idea on quickly calculating the range of your Wireless device using Transmit power and Receiver sensitivity.
I was wondering why they have not mentioned the transmission distance in the datasheet?. This was the same case for most of the devices i searched.
All of the chip manufacturers mentioned the RF range of their wireless device in terms of Transmit power and Receiver sensitivity.
To calculate the RF range you need to understand the term Link budget.
The Transmit power and receiver sensitivity are specified in dBm.
dBm – relative to 1 mW
10mW = 10dBm, 0dBm = 1mW
-110dBm = 1E-11mW = 0.00001nW
Rules of thumb :
- Double the power = 3 dB increase
- Half the power = 3 dB decrease
120 dB link budget at 433 MHz gives approximately
2000 meters (Chipcon rule of thumb)
- 6 dB improvement ~ twice the distance
- Double the frequency ~ half the range
- 433 MHz has longer range than 868 MHz
Using the above rules we can calculate approximate range of RF devices ,
If we want to find the range of 2.4GHz RF devices then using the above information,
120dB link budget @ 433 MHz gives 2000 meters
120dB link budget @ 866 MHz gives 1000 meters (double the frequency ~ half the range using rules above)
120dB link budget @ 1732 MHz gives 500 meters
120dB link budget @ 3464 MHz gives 250 meters
So, 120dB link budget @ 2400 MHz gives approximately 360 meters range
Look at the specs below from TI CC24xx wireless device which show that the range is doubled with a increase in link budget by 6 dBm