E9B01
ANTENNAS AND TRANSMISSION LINES · Antenna patterns and designs: azimuth and elevation patterns; gain as a function of pattern; antenna modeling
E9B01E9B →
What is the 3 dB beamwidth of the antenna radiation pattern shown in Figure E9-1?
- A75 degrees
- B50 degrees
- C25 degrees
- D30 degrees
Why The 3 dB beamwidth is the total angular width of the main lobe measured between the two points where the radiated power has fallen to half (3 dB below) the peak value. On Figure E9-1 you locate the peak of the major lobe, step in one ring to the 3 dB down circle, and read the bearing where the pattern crosses it on each side of the peak. Those crossings are about 25 degrees either side of the lobe axis, so the full beamwidth is 50 degrees.
Watch out The choice saying 25 degrees is the half-beamwidth, the angle from the lobe center out to one 3 dB point, not the width between both points; 75 degrees is closer to where the pattern has dropped much further down, near the lobe edges or nulls.
Beamwidth spans both sides of the peak: find one 3 dB point, then double the angle.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
The rest of E9B
- E9B01 What is the 3 dB beamwidth of the antenna radiation pattern shown in Figure E9-1?
- E9B02 What is the front-to-back ratio of the antenna radiation pattern shown in Figure E9-1?
- E9B03 What is the front-to-side ratio of the antenna radiation pattern shown in Figure E9-1?
- E9B04 What is the front-to-back ratio of the radiation pattern shown in Figure E92?
- E9B05 What type of antenna pattern is shown in Figure E9-2?
- E9B06 What is the elevation angle of peak response in the antenna radiation pattern shown in Figure E9-2?
- E9B07 What is the difference in radiated power between a lossless antenna with gain and an isotropic radiator drive…
- E9B08 What is the far field of an antenna?
- E9B09 What type of analysis is commonly used for modeling antennas?
- E9B10 What is the principle of a Method of Moments analysis?
- E9B11 What is a disadvantage of decreasing the number of wire segments in an antenna model below 10 segments per ha…