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TV Antennas for Distance Receiving

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ANTENTOP- 01- 2015, # 019 TV Antennas for Distance Receiving

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1 Rhombic Antenna

 

 

Figure 2 Rhombic antenna is Combination of Four Wires with Traveling Wave

 

 

Table 1 shows data for Rhombic Antenna with different parameters. To keep such parameters antenna should be placed above the ground at height not less the 2- 3 wavelength of the working band of the antenna.

 

Antenna may be fed by open ladder line with wave impedance 300 600- Ohm. At this case the antenna could be matched at all working frequencies band. Antenna may be fed through a coaxial cable when two simple matching transformers are used. Figure 3 shows feeding Rhombic Antenna through a coaxial cable. First transformer is a broadband transformer made on two wire ladder line. It is two wires line with varying wave impedance on the length.

The wave impedance of the line changes from 700- Ohm at rhomb side to 300- Ohm at coaxial cable side.At coaxial cable side the coaxial cable should not connect straight away to the line. Coaxial cable connected to the line through a symmetrical transformer 4:1 made on lengths of the used coaxial cable. The transformer makes symmetrical and provides matching of the Rhombic Antenna to coaxial cable. Loop of the coaxial cable should have electrical length lambda/2. To calculate such transformer you need to know the shortening coefficient of the used coaxial cable.

 

 

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Last Updated:

May 1, 2016 22:19

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