ANTENTOP- 01- 2012, # 016

Ground Plane Antenna for 40, 20, 15 and 10- meter Bands

The ATU has a closed stub made of a coaxial cable with electrical length 1.25- lambda for the 15- meter Band. At the band the stub has high resistance impedance and antenna is tuned with help L1 and C1. At the 20- meter band the stub has capacitance impedance what is needed to match the antenna at the band. At 10- meter band the stub has inductance impedance what is needed to match the antenna at the band.

At the 40- meters band a lengthening inductor L2 is used to match the antenna. The inductor is closed with help of Relay K1 at the other bands.

Good match of the antenna is possible only on one band- 15- meter. At the other bands the match is only satisfactory. Figure 4 shows design of the antenna base with ATU. ATU should be placed into weather- proofed plastic or metal box.

Item 1: Porcelain Base Insulator

Item 2: Span- Counterpoise

Item 3: Lengthening Inductor L2

Item 4: Radiator Base

Item 5: Radiator

Item 6: Antenna Support Base Tube

Item 7: Feeder and Closed Stub

Four counterpoises were used with the antenna. Each counterpoise had length 530- cm, diameter 2- mm and was installed at 45- degree to the Antenna Support Base Tube. Metal roof may be used instead of the counterpoises in case if the antenna is installed above such roof. Vertical radiator made of from an aluminum tube in diameter 4- cm and has length 530- cm.

Original ATU was calculated to match the antenna with coaxial cable 88- Ohm. Table 1 gives data for the ATU for coaxial cables 88-, 50- and 75- Ohm.

Figure 4 Design of the antenna base with ATU

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