FEM issue

RE: FEM issue

stak — Tue, 28 Jul 2026 12:23:12 GMT

You are right. It seems the errata is not relevant there.

The RFX2401C uses a standard 2-pin control interface, which is supported by the nRF54L15 through the Simple GPIO FEM interface.
However, we only validate and test the Skyworks FEMs listed in our supported devices table. When using a different FEM, such as the RFX2401C, it is the customers responsibility to verify that the DeviceTree configuration and GPIO timing parameters meet the requirements of your hardware.

Based on standard configuration for supported skyworks ctx-settle-time-us and crx-settle-time-us should be assigned acoordingly to:
sdk-nrf/dts/bindings/radio_fem/skyworks,sky66112-11.yaml at main · nrfconnect/sdk-nrf
I see that you are setting it to 1us. Please check that these are configured properly.

Let me know how it goes!

Edit: Also check nRF54L section in https://nrfconnectdocs.nordicsemi.com/ncs/latest/nrf/app_dev/device_guides/fem/fem_simple_gpio.html

RE: FEM issue

larry ding — Tue, 28 Jul 2026 09:40:55 GMT

Sorry, but we don't understand why this errata may degrade range. It said the power emitted might exceed regulatory limits.

RE: FEM issue

stak — Mon, 27 Jul 2026 16:03:13 GMT

Hi,

I’m still looking into the issue, but one thing worth checking is whether your nRF54L15 is affected by this Errata: https://docs.nordicsemi.com/r/bundle/errata_nrf54l15_rev1/page/err/nrf54l15/rev1/latest/config_l15_56.html. (Check your revision) The errata specifically applies to the nRF54L15 and describes an issue with external FEM/PA operation, which can degrade range.

There may also be some impact from interference in the test environment, or other explanations, but I would recommend reviewing the errata and trying the proposed workaround as a starting point.

Stine

RE: FEM issue

skylu@telit — Mon, 27 Jul 2026 10:28:11 GMT

we use RFX2401C.

the FEM should have configured correctly. because with FWM device and SCAN and connection other BLE devices

here is the DTS

&radio {
fem = <&nrf_radio_fem>;
};

/ {
nrf_radio_fem: rfx2401c_fem {
compatible = "skyworks,rfx2401c", "radio-fem-two-ctrl-pins";

/* TXEN -> P1.10 ; RXEN -> P0.01 */
ctx-gpios = <&gpio1 10 GPIO_ACTIVE_HIGH>;
crx-gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;

ctx-settle-time-us = <1>;
crx-settle-time-us = <1>;

tx-gain-db = <25>;
rx-gain-db = <12>;
};
};

here is the config

# MPSL + FEM simple GPIO control

CONFIG_MPSL=y

CONFIG_MPSL_FEM=y

CONFIG_MPSL_FEM_SIMPLE_GPIO=y

RE: FEM issue

PaKa — Mon, 27 Jul 2026 09:57:26 GMT

Which FEM are you using and are you sure it is configured correctly?