Window Dipole Antennas with Capacitive Loads _007

ANTENTOP- 01- 2005, # 007		Window Dipole Antennas with Capacitive Loads



		by Igor Grigorov, VA3ZNW
It is possible to install a dipole antenna with capacitive loads for the 6 and 10 meters bands at a standard window with sizes 140x150 or 140x210 centimeters. The design of that window antenna for the bands can be simple as well as the antenna impedance can be easy matched with 50-Ohm coaxial cable. That dipole antenna with capacitive loads installed at upper floor of a high-rise building can provide DX- QSOs. However, a dipole window antenna with capacitive loads for bands low the 10-meters, if this one is installed at a standard window with sizes 140x150 or 140x210 centimeters, has low input impedance and narrow bandwidth so the antenna is hard to match. Hence antennas for bands low the 10 meters are not discussed in this article. Types of a Dipole Antenna with Capacitive Loads There is several ways to install a dipole antenna with capacitive loads at a window. The best way is to install a dipole antenna with capacitive loads by the center of the window. In that case the antenna can be installed at any house as made from a brick or wood as well as made from a concrete. Let's name the antenna "antenna central installation." If a house made of a brick or wood it is possible to install the dipole antenna with capacitive loads by up or down of the window. Let's name the antenna "antenna up or down installation." Of course, a non metal window-frame works better the metal one. Feeding Coaxial Cable of a Dipole Antenna with Capacitive Loads Ferrite rings (5- 20 ring with any permeability) installed at two ends of the coaxial cable going from TX to the antenna prevent RF- currents going from the antenna to TX. Since the rings do balun job. Fasten the rings at the coax with a Scotch. The coaxial cable going from the antenna to the window-sill should be placed athwart to the antenna. However the coaxial can be placed as you want at you room.		Stuff for a Dipole Antenna with Capacitive Loads A dipole antenna with capacitive loads can be made of a flexible multi- wire cable as well as of a strand wire. Any wire is good as naked as well covered by plastic isolation. Diameter of the wire can be near 1- 2 millimeters (12- 18 AWG). Use wire as much thick as possible. Compare to antenna made from thin wire thick antenna has wider bandwidth. It is wise (because it is cheap) to do a dipole antenna with capacitive loads without ends insulators. The antenna can be installed with help of a rope or plastic (as well as fishing) cord. A dipole antenna with capacitive loads of up or down installation can be installed directly (with help of nail or staple) at plastic or wooden window frame. Window Dipole Antennas with Capacitive Loads for 6-meters Band Figure 1 shows a schematic (Figure 1a) and design (Figure 1b) of a window dipole antenna with capacitive loads of central installation. Figure 2 shows a schematic of a window dipole antenna with capacitive loads of up or down installation. The design of the antenna is similar to design shown at Figure 1b. The design of the both antennas is simple. Two ropes are installed at two ends of the window. Capacitive loads fastened to the ropes by thin wires or ropes. Third rope is installed at the center of the window. Antenna central insulator (made from a piece of any plastic or PC board) is fastened to the rope. Figure 1 A window dipole antenna with capacitive loads of central installation

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