Estimating the range of nRF52840

[ill ai]

Hi all,

I have been learning and doing research trying to estimate the range of a bluetooth chip. So far I've got to use Friis Transmission Equation to estimate the distance but it didnt seen right. And then I watched a video published by Nordic Semiconductor about testing the range of nRF52840

https://www.youtube.com/watch?v=w4PbxVwg83M

which mentioned that nRF52840 can attain ~750m with some signal to spare.

while with my data and calculation based on Friis Transmission Equation:

Antenna Gain(both receive and transmit): 0dB

Tx Power: 8dBm

Rx Sensitivity: -103dBm (125kbs)

Path loss: ~104Frequency: 2400Mhz

The answer I got from the above is: 2.19miles/ 3.519km.

Which to me is a bit nonsense.

Could someone explain it for me? Is there anything missing in my calculation? Or there reeally is a huge difference between practical data and theoretical data?

Data are based on the specification shown below

https://www.nordicsemi.com/-/media/Software-and-other-downloads/Product-Briefs/old-versions/nRF52840PBv20.pdf?la=en&hash=516968A8D06D7F41C8B14B6639DD9E14099E2853

And the equation I used was from the link blow, which should be quite convincing( as I've search for more then 3 websites suggesting the same equation to me)

https://www.allaboutcircuits.com/technical-articles/wireless-range/

[awneil]

ill ai said:

Path loss: ~104Frequency: 2400Mhz

What "path" is that? 

Open, free space has a very different path loss to Real Life with obstructions, interference, etc, etc, 

Fanstel have a good report on practical range measurement:

www.fanstel.com/testreport

[ill ai]

Sorry I didn't provide all information I have.

The equation was from this link:https://www.allaboutcircuits.com/technical-articles/wireless-range/

Sure I know the difference between how BT working in free space and in urban area.

the "path" i am referring to here is the one similar to the environment in the youtube video.

[awneil]

I added this - possibly after you replied:

Fanstel have a good report on practical range measurement:

www.fanstel.com/testreport

[ill ai]

Thanks for the report!
its useful to me really.

But I still want to know the estimation based on calculation, even a fairly rough one.

[ketiljo]

Theoretically, that's correct what you say. 3.5 km gives a path loss of ~111 dB. So in ideal conditions, you should have 3 km +. But as soon as you have obstacles between the two sides of the link, noise near by, etc. the range will drop.

[awneil]

plus, of course, the antenna and the practical hardware are not perfect.

[ill ai]

thanks very much for the report~
 ketiljo's answer resolve half of my doubt and your website was a crucial support