https://devzone.nordicsemi.com/f/nordic-q-a/57844/rearranging-mistakes-in-antennas-dbiI see the messy information elsewhere especially in selling infos about antennas for BLE5. OK optimal antenna is a quarter length of average wavelength -( 299 792 458 ) / ( ((2402+2485)/2=2443.5) * 10E+9 ) ) / 4 = 30.67 mm. But dbm value varies fromen-USTelligent Community 13Mon, 17 Feb 2020 12:09:05 GMThttps://devzone.nordicsemi.com/thread/234626?ContentTypeID=1Mon, 17 Feb 2020 12:09:05 GMT137ad170-7792-4731-bb38-c0d22fbe4515:32e88c15-0338-4359-9588-b910f936588cAndreas<p>Hi,</p> <p>&nbsp;</p> <p>Your calculation for a quarter wave monopole antenna assumes speed of light in vacuum, which will not give an accurate estimate when surrounded by air/PCB substrate. See this whitepaper:&nbsp;<a href="https://infocenter.nordicsemi.com/pdf/nwp_008.pdf?cp=14_19">https://infocenter.nordicsemi.com/pdf/nwp_008.pdf?cp=14_19</a></p> <p>The length of the antenna is also affected by the size of the&nbsp; ground plane, surroundings, etc. making it hard to calculate accurately. We recommend that you tune the antenna for optimal performance, see this whitepaper:&nbsp;<a href="https://infocenter.nordicsemi.com/pdf/nwp_017.pdf?cp=14_12">https://infocenter.nordicsemi.com/pdf/nwp_017.pdf?cp=14_12</a></p> <p>Still, even with a good antenna the received signal power will vary a lot due to multipath and fading.</p> <p>&nbsp;</p> <p>If you are uncertain about your antenna design I recommend that you submit it here for a free review.</p> <p>&nbsp;</p> <p>Best regards,</p> <p>Andreas</p><div style="clear:both;"></div>