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Andy aka
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There is a standard formula for calculating how much the power is attenuated between two antennas. It is this: -

Link Loss (dB) = 32.4 + 20\$log_{10}\$(F) + 20\$log_{10}\$(d)

where F is MHz and d is distance between the two antennas (kilometres).

In short, if you are transmitting at 500MHz over a distance of 2kM, the link loss is

32.4dB + 54.0dB + 6.0dB = 92.4dB.

If the distance were 200 metres the link loss would be 32.4dB + 54.0dB -14.0dB = 72.4dB.

This is the loss between two objects without the hindrance of the earth getting in the way. The antennas assumed are so-called isotropic antennas (which transmit equally in all directions). Should you have an antenna with gain (such as a dipole) at each end you can reduce the loss by about 3.5dB. Should you have higher gain antennas then the losses reduce even more but directionality may become an issue.

Next is how much power does the receiver need to reasonably guarantee moderate data success and there is a formula for this too: -

Power required in dBm is -154dBm + 10\$log_{10}\$(data rate) dBm

If the data rate is 1Mbps then the power required is -154dBm + 60dBm = -94dBm

From this you can calculate the power out needed by your transmitter. But of course you need to take into account the different effects produced by the presense of the earth and atmosphere which I'll leave for you to research.

There is a standard formula for calculating how much the power is attenuated between two antennas. It is this: -

Link Loss (dB) = 32.4 + 20\$log_{10}\$(F) + 20\$log_{10}\$(d)

where F is MHz and d is distance between the two antennas (kilometres).

In short, if you are transmitting at 500MHz over a distance of 2kM, the link loss is

32.4dB + 54.0dB + 6.0dB = 92.4dB.

If the distance were 200 metres the link loss would be 32.4dB + 54.0dB -14.0dB = 72.4dB.

This is the loss between two objects without the hindrance of the earth getting in the way. The antennas assumed are so-called isotropic antennas (which transmit equally in all directions. Should you have an antenna with gain (such as a dipole) at each end you can reduce the loss by about 3.5dB. Should you have higher gain antennas then the losses reduce even more but directionality may become an issue.

Next is how much power does the receiver need to reasonably guarantee moderate success and there is a formula for this too: -

Power required in dBm is -154dBm + 10\$log_{10}\$(data rate) dBm

If the data rate is 1Mbps then the power required is -154dBm + 60dBm = -94dBm

From this you can calculate the power out needed by your transmitter. But of course you need to take into account the different effects produced by the presense of the earth and atmosphere which I'll leave for you to research.

There is a standard formula for calculating how much the power is attenuated between two antennas. It is this: -

Link Loss (dB) = 32.4 + 20\$log_{10}\$(F) + 20\$log_{10}\$(d)

where F is MHz and d is distance between the two antennas (kilometres).

In short, if you are transmitting at 500MHz over a distance of 2kM, the link loss is

32.4dB + 54.0dB + 6.0dB = 92.4dB.

If the distance were 200 metres the link loss would be 32.4dB + 54.0dB -14.0dB = 72.4dB.

This is the loss between two objects without the hindrance of the earth getting in the way. The antennas assumed are so-called isotropic antennas (which transmit equally in all directions). Should you have an antenna with gain (such as a dipole) at each end you can reduce the loss by about 3.5dB. Should you have higher gain antennas then the losses reduce even more but directionality may become an issue.

Next is how much power does the receiver need to reasonably guarantee moderate data success and there is a formula for this too: -

Power required in dBm is -154dBm + 10\$log_{10}\$(data rate) dBm

If the data rate is 1Mbps then the power required is -154dBm + 60dBm = -94dBm

From this you can calculate the power out needed by your transmitter. But of course you need to take into account the different effects produced by the presense of the earth and atmosphere which I'll leave for you to research.

Source Link
Andy aka
  • 473.1k
  • 29
  • 383
  • 839

There is a standard formula for calculating how much the power is attenuated between two antennas. It is this: -

Link Loss (dB) = 32.4 + 20\$log_{10}\$(F) + 20\$log_{10}\$(d)

where F is MHz and d is distance between the two antennas (kilometres).

In short, if you are transmitting at 500MHz over a distance of 2kM, the link loss is

32.4dB + 54.0dB + 6.0dB = 92.4dB.

If the distance were 200 metres the link loss would be 32.4dB + 54.0dB -14.0dB = 72.4dB.

This is the loss between two objects without the hindrance of the earth getting in the way. The antennas assumed are so-called isotropic antennas (which transmit equally in all directions. Should you have an antenna with gain (such as a dipole) at each end you can reduce the loss by about 3.5dB. Should you have higher gain antennas then the losses reduce even more but directionality may become an issue.

Next is how much power does the receiver need to reasonably guarantee moderate success and there is a formula for this too: -

Power required in dBm is -154dBm + 10\$log_{10}\$(data rate) dBm

If the data rate is 1Mbps then the power required is -154dBm + 60dBm = -94dBm

From this you can calculate the power out needed by your transmitter. But of course you need to take into account the different effects produced by the presense of the earth and atmosphere which I'll leave for you to research.