fmradio
Electrical
- Oct 6, 2004
- 37
thread247-93327
The following statement was posted on 6 Oct 2004 in the referenced thread: "In FM and TV broadcast transmit antennas, the cavity-backed radiator has about the lowest (true) c-pol axial ratio, as installed."
In support of that statement, the attached gif shows the measured, h-plane axial ratio of such an antenna. The fine ripple shown on the pattern is a measure of the true, c-pol axial ratio of that design, and is produced when the antenna/tower section under test are rotated slowly on its vertical axis while recording the output voltage of the antenna operating in receive mode. The transmit antenna used as the source during the measurement was a rapidly rotating, linear dipole.
The following statement was posted on 6 Oct 2004 in the referenced thread: "In FM and TV broadcast transmit antennas, the cavity-backed radiator has about the lowest (true) c-pol axial ratio, as installed."
In support of that statement, the attached gif shows the measured, h-plane axial ratio of such an antenna. The fine ripple shown on the pattern is a measure of the true, c-pol axial ratio of that design, and is produced when the antenna/tower section under test are rotated slowly on its vertical axis while recording the output voltage of the antenna operating in receive mode. The transmit antenna used as the source during the measurement was a rapidly rotating, linear dipole.