ANTENTOP- 01- 2016 # 020

UA6AGW Antenna V. 20-10.51 (14.0- 29.5- MHz)

Inner tube was in 14- mm diameter and outer tube was in 18- mm diameter. In folded position the horizontal wire has length in 1.6- meter. Outer tube holds the inner tube with help of a clamp. Figure 5 shows assembled UA6AGW Antenna V. 20-10.51. Figure 6 shows center (with a clamp) of the horizontal wire.

Home brew "butterfly" variable capacitor is used for tuning the antenna. Plates of the capacitor made of galvanized iron in 0.5- mm thickness. Capacitor has seven stator plates and six rotor plates. Bolts in 5.0- mm diameter hold the plates. Spacer for the plates are nuts. Figure 7 shows the capacitor. Additional capacitor (for 20- and 17- meter bands) made from a length of a coaxial cable. The capacitor is connected to bridge to the variable capacitor. It is easy to do because the connection points are accessible in the field. Connection points are placed on the horizontal wires. Figure 8 shows the additional capacitor.

Capacitor is tuned with help of servo motor HS-311 with standard hardware (Reference 3). Figure 9 shows servo motor installed on to the variable capacitor.

To operate the servo motor it was made a special control box. The box was made on the base of China servo tester HJ (Reference 4). Figure 10 shows the Control Box. Table on the box shows data displayed on the servo tester to tune the capacitor for needed band of operation.

Figure 5 Assembled UA6AGW Antenna V. 20-10.51

Figure 7 Capacitor of the UA6AGW Antenna V. 20-10.51

Figure 8 Additional capacitor made of a length of coaxial cable

At the servo tester it was installed a big dial (instead a small one) for the fine tune. Servo tester may be feed by 4.8- 6.0- V. To feed the servo motor it was used a LAN cable between the control box and those one.

Coupling Loop made of from 50- Ohm coaxial cable. Length of the coaxial cable to be used for the coupling loop is 400- mm. Figure 11 shows the preparation of the coaxial cable for coupling loop before it was formed to loop shape. Plastic from the length of the coaxial cable is removed on to 10- mm in the center and from two ends. Then braid of the coaxial cable is removed at the center. Inner conductor is soldered to the braid at the far (right) end of the length.

Then the cable is turned to loop. Far end of the length is soldered to the first (left) side of the prepared cable. The coupling loop is fastened to the upper part of the antenna's loop with help of a Scotch and ties. Below there are several simple rules how to install the coupling loop.

At first, find on the antenna loop a point that is equidistance from left and right side of the C2. It is the point of symmetry of the antenna.

At second, find the point of symmetry of the coupling loop. The coupling loop is mounted in the top of the antenna loop. Point of symmetry of the coupling loop should concur with the point of symmetry of the antenna.

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