ANTENTOP- 01- 2015, # 019

Table 1 Data for Rhombic Antenna with Different Parameters

It is possible to use coaxial cable with any wave impedance- 50 or 75 Ohm. Matching impedance of the 4:1 transformer depends on the coaxial cable. At 50- Ohm cable it is got transformer 200:50- Ohm, at 75- Ohm cable it is got transformer 300:75- Ohm. Transformer 300:75- Ohm should have best matching result with open line transformer. There are lots link in the internet how the transformer may be calculated. One of them is:

http://www.n-lemma.com/calcs/dipole/balun.htm.

When the coaxial cable symmetrical transformer is used the broadband of the antenna depends on the broadband of the transformer. As usual coaxial cable transformer has good matching at the 5% frequencies band calculated from the central working frequency of the transformer. So, when such transformer is used the broad band of the Rhombic Antenna is limited to pass band of the transformer.

Antenna may be made from a strand wire in diameter 2- 3- mm. It may be copper, aluminum or bimetal (with copper or aluminum layer) wire. Terminated resistor at the antenna may be any small power non-inductive resistor. This one should be protected from atmospheric influences.

Figure 3 Feeding Rhombic Antenna through Coaxial Cable

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