Therefore, anywhere along the side-lobe direction from this transmitter, a blind receiver could not tell the difference if the Yagi-Uda was replaced with an isotropic radiator with antenna input power increased by 1.57 dB.
12.
Where G _ t and G _ r are the antenna gains ( with respect to an isotropic radiator ) of the transmitting and receiving antennas respectively, \ lambda is the wavelength, and R is the distance between the antennas.
13.
In reality, a " continuous vector field tangent to the surface of a sphere must fall to zero at one or more points on the sphere, which is inconsistent with the assumption of an isotropic radiator with linear polarization.
14.
Due to reciprocity, these two effects are equal-an antenna that makes a transmitted signal 100 times stronger ( compared to an isotropic radiator ), will also capture 100 times as much energy as the isotropic antenna when used as a receiving antenna.
15.
Higher gain rating ( dBi ) indicates further deviation ( generally toward the horizontal ) from a theoretical, perfect isotropic radiator, and therefore the further the antenna can project a usable signal, as compared to a similar output power on a more isotropic antenna.
16.
Therefore, anywhere along the side-lobe direction from this transmitter, a blind receiver could not tell the difference if a Yagi-Uda was replaced with either an ideal dipole ( oriented towards the receiver ) or an isotropic radiator with antenna input power increased by 1.57 dB.
17.
Therefore, an antenna with a peak power gain of 5 would be said to have a gain of 7 dBi . " dBi " is used rather than just " dB " to emphasize that this is the gain according to the basic definition, in which the antenna is compared to an isotropic radiator.
