The nRF21540 DK is equipped with two small coaxial connector (J1 and J7) for measuring the RF signal with a spectrum analyzer.
The connector is an SWF type (Murata part no. MM8130-2600) with an internal switch. By default, when no cable is attached, the RF signal is routed to the onboard chip antenna.
A test probe is available (Murata part no. MXHT83QE3000 ) with a standard SubMiniature Version A (SMA) connector on the other end for connecting instruments. When connecting the test probe, the internal switch in the SWF connector disconnects the onboard antenna and connect the RF signal from the nRF21540 to the test probe.
When measuring, consider that the connector and test probe adds loss to the RF signal. See the following table for more information.
| Frequency (MHz) | Loss (dB) |
|---|---|
| 2440 | 1.0 |
| 4880 | 1.7 |
| 7320 | 2.6 |