special tuning for underwater application

[Fabien Comte]

Hello,

Is that possible to force carrier frequency out of 2.4 GHz band (modify canals) for a special underwater application (2.4 GHz is not adapted so i whish to move on another band but keeping nrf51 with bluetooth on 2 the 2 sides of the link) ?

Is there any way to use an external power amplifier to boost signal ?

[Dave_couling]

This is possible, but I'm not sure if its possible with the nRF51 chip. I've done some work in these applications and used Zigbee instead.

[MartinBL]

Hi. No this is not possible. You can only change the carrier frequency to 2.5 GHz on the nRF51. You will need to go much lower than that to get any range at all under water.

Using a power amplifier to boost signals in air is possible though. Here is a relevant application note: Range Extension for Nordic nRF51 Series with RFaxis RFX2411N RFeIC.

[Fabien Comte]

Thank you for your response.

How to change to 2.5 GHz ?

No way to do a test at 868 MHz with an internal PLL setting ? If i change quartz ?

[MartinBL]

You can set the register RADIO->FREQUENCY = 100. Have a look at Chapter 17.1 and 17.2 in the Reference Manual v3.0.

There is no way to change the PLL settings or use frequencies below 2.4GHz.

[Fabien Comte]

Ok thank you