J POLE ANTENNA:
J pole antenna is one of the popular antenna with 2meter in height commonly used in amateur radios particularly on VHF and UHF bands. It was fi invented by Hans Beggerow in 1909. It was used in zeppelin airships. It is end fed vertical half wavelength antenna. It is also known as J antenna and end fed zepp. It is omnidirectional in nature. When j pole antenna is properly connected , it clearly makes good match for 50 ohm coaxial transmission line. Commonly impedance matching is done for J pole antenna. The transmitter is matched to output impedance by a series band section of transmission line. The Jpole antenna is more sensitive to metal objects in surroundings. This is due to lack of true ground plane. This can be reduced by feed polarity. It can be avoided by making a distance of one or two wavelength away from filling cabinets.
J pole antenna is of different types,
• Roll up emergency J pole
• Copper pipe J pole
• Fold up copper pipe J pole
• Double Jpole
• Super J pole
Roll up emergency antenna is trivial to build. The disadvantage of this antenna is , fairly fragile and has narrow bandwidth because of small diameter of the wires. The bandwidth can be increased by the usage of ladder line for impedance match. And also by connecting piece of coax to the radiating part. The construction of copper pipe J pole is ease for durability and bandwidth. Fold up copper pipe J pole antenna is too large and hard to carry. It has small durability. The antenna which consist of number of half wavelength vertical elements separated with half wavelength tuning stubs feed with folded matching stub is called Super J pole antenna. It is co-linear vertical antenna .
J pole antenna is one of the popular antenna with 2meter in height commonly used in amateur radios particularly on VHF and UHF bands. It was fi invented by Hans Beggerow in 1909. It was used in zeppelin airships. It is end fed vertical half wavelength antenna. It is also known as J antenna and end fed zepp. It is omnidirectional in nature. When j pole antenna is properly connected , it clearly makes good match for 50 ohm coaxial transmission line. Commonly impedance matching is done for J pole antenna. The transmitter is matched to output impedance by a series band section of transmission line. The Jpole antenna is more sensitive to metal objects in surroundings. This is due to lack of true ground plane. This can be reduced by feed polarity. It can be avoided by making a distance of one or two wavelength away from filling cabinets.
• Roll up emergency J pole
• Copper pipe J pole
• Fold up copper pipe J pole
• Double Jpole
• Super J pole
Roll up emergency antenna is trivial to build. The disadvantage of this antenna is , fairly fragile and has narrow bandwidth because of small diameter of the wires. The bandwidth can be increased by the usage of ladder line for impedance match. And also by connecting piece of coax to the radiating part. The construction of copper pipe J pole is ease for durability and bandwidth. Fold up copper pipe J pole antenna is too large and hard to carry. It has small durability. The antenna which consist of number of half wavelength vertical elements separated with half wavelength tuning stubs feed with folded matching stub is called Super J pole antenna. It is co-linear vertical antenna .
No comments:
Post a Comment