Rearranging mistakes in antennas dbi.

I 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 from 1.1 dbm to 11 dbm.

Maybe Ohm resistance of that piece of wire ... sorry usual Whip type antenna with cable from U.FL to SMA-antenna

Maybe Nordic have Guide about it to clear matter ???