nRF52833 Mesh range questions

[Sean Taylor]

We are evaluating chipsets for an IoT mesh solution and a key requirement is maximum range - data throughput will be very low.  The module vendor we would likely choose supports nRF52833 with 8dBm max Tx power.  (They also have nRF52832 with 20dBm for US only - but no coded PHY in 52832)

I estimate with an omni antenna (chip/PCB trace on module) and 8dBm the max. distance between mesh nodes would be around 25-30 meters, assuming no obstructions, based on some experiments I performed - does this seem about right ?

It would be great to be able to combine BLE mesh with coded PHY - I understand this is not supported by Bluetooth standard, and I have seen some posts on devzone that this can be made to work with the nRF52833 - could anyone confirm or otherwise?  What is the latest status ?

Assuming we can make mesh with coded PHY, and assume approx 8dB increase in receiver sensitivity this would translate to just over double the range - say 50-70 meters ?  (6dB = double range assume inverse square propagation, real life is worse).

One reads about Bluetooth links over hundreds of meters with 4dBm transmitters - I get nowhere near this distance, so I assume they must use directional antennas + coded PHY ?

Thanks for any help.

[Hung Bui]

Hi Sean, 

Please be aware that if you do BLE mesh with coded PHY you may not be able to pass Bluetooth qualification. 

Could you let me know the environment when you test the range. And how did you test ? Do you have any casing that covers the antenna ? 

At +4dBm and outdoor light of sight , you should easily reach 50-100m with the omni antenna.
But you need to test using tuned (optimized) hardware. Our nRF52 DK is something you can use to test the range. 

Our long range tests showed the range of 654m without coded PHY and 1300m with coded PHY, this is with 0dBm output. 

https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/testing-long-range-coded-phy-with-nordic-solution-it-simply-works-922075585

[Sean Taylor]

Hi Hung, 

Thanks for the quick reply.

I discovered that by disabling the power to the JTag interface circuit on the dev. kit the range of my kit (not Nordic) increased the range to approx. 40m at 6dBm - roughly in line with the 50-100m @4dBm you mention (perhaps this dev kit is not so optimized, or perhaps there is a lot of 2.4GHz noise in my location -e.g. wifi).

However I don't understand how your expectation of 50-100m at 4dBm Tx power then translates to a measured range of 650m at 0dBm (also with an omni antenna).  A factor of 10 greater range implies 18+dB greater link loss.

My next step is to order two nRF52840 dev. kits and I'll see what range I get with those - whether closer to the 50-100 you state or the 650m in your link.

[Hung Bui]

Hi Sean, 

I'm sorry that it's a bit confusing. 

The 654m was tested at complete flat surface with no interference. The communication is also at minimum level (you will experience lots of packet drop at this range).

I mentioned 50-100m can be "easily reach" at +4dBm, it's not the max range. 

[SRINATH]

Hi Hung,

What type of trace antenna is used in nrf52833 dk?

Is it an omni directional antenna?