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Window Dipole Antennas with Capacitive Loads

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ANTENTOP- 01- 2005, # 007  

Window Dipole Antennas with Capacitive Loads

 

 

Figure 1 A window dipole antenna with capacitive loads of central installation

 

Figure 2 A window dipole antenna with capacitive loads of up or down installation

 

Adjustment of the both antennas is simple. A SWR- meter or HF- bridge (see References [1]) is connected to feed points of the tuned antenna. Gradually shorten ‘moustaches’ (symmetrically each moustache) of the antenna to minimum SWR or when antenna input impedance is active (has no reactive component) at needed frequency. At shortening moustaches the moustache wires roll up to a little coil.

 

Parameters of the Window Dipole Antenna with Capacitive Loads of Central Installation

 

Theoretical parameters of the antennas (copper, wire in 1-mm (18- AWG) diameter) were simulated with help of MMANA (see References [2]).

Figure 3 shows the input impedance of the antenna installed at window 150-cm wide. Figure 4 shows the input impedance of the antenna installed at window 210-cm wide. 

Theoretical input impedance for ‘narrow’ antenna is 42- Ohms, for ‘wide’ antenna is 60- Ohms. The data are very good matched with my practical measurement of the antennas. A 50- Ohm coaxial cable should be used for feeding of the antennas. This one can be connected directly to antenna feed points, as it is shown at Figure 1. A 75- Ohm coaxial cable is possible to use for the antenna installed at wide (210 cm) window. Figure 5 shows a SWR at 50- Ohm coaxial for ‘narrow’ antenna shown at Figure 1. Figure 6 shows a SWR at 50- Ohm coaxial for ‘wide’ antenna shown at Figure 1. Theoretical gain for the antennas is near 1,5- 1,7 dBi.

 

Figure 3 Input impedance of ‘narrow’ antenna

 

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