Problem with connection when i cover the circuit with hand

[Paolo]

Good evening everyone,

i'm starting to program with the nRF52832 development board
and i am testing the example programs. I started with the project:

- ble_app_hts_pca

The device connects successfully with the Android app when the
connection occurs in free space.
If i close the board in my hands, the connection stops working and
the app no longer receives the temperature data.

Can you help me to understand why this happens.

If I use a headset and put the antenna completely in my hands 
transmission is successful and sound is good..

[awneil]

Paolo said:

why this happens

Water is excellent at blocking transmission of 2.4GHz.

Your hand is around 60% water

[Paolo]

How can i fix that? We are working on a body patch that is not completely covered
by human skin. Only one side is attached on the skin. The other part is free. 

[Kenneth]

The device's antenna must be tuned where it is intended to used, the plastic casing must be available to do this tuning. If you take a board and shield in your hand without tuning and no plastic, then it won't work no. The human body is an efficient blocker for 2.4GHz, so it will mostly rely on reflections from surroundings if you plan to place it on the human body and there is no line of sight to the peer. So it is important that the board have been properly reviewed and tuned with prototype plastic. This is something we can help you with if you create a confidential case and ask for a layout review as a first step.

[Paolo]

Ok about tuning. Please let me know if tuning can be done by firmware or we need to modify the antenna.
We are usind ISP module that is based on Nordic IC, that means that we cannot work on antenna directly, but only by SW.

[Kenneth]

You may check with the vendor of the module in terms of placement and where/how they recommend placement relative to the human body, casing and motherboard.

It's very little that can be done in SW here, you may increase output power if you haven't.

Best regards,
Kenneth

[Paolo]

We try with more power, and is going better.. but we need more efficiency!

[Kenneth]

It may be possible to adjust the antenna, however if you have bought a module from a third party, then this module is likely pre-certified/pre-qualified, it may be difficult to do changes then. So in that case I recommend to check with the vendor of the module to make sure you have mounted their module according to their specifications. It can be a tremendous difference in performance if you have not followed their guidelines.