ANTENTOP- 01- 2013 # 017

Modifications for the Multiband UB5UG Antenna

Figure 1 Modified Multiband UB4UG Antenna

The ATU makes a good match of the antenna with a TX output (SWR close to 1.0:1.0) and eliminates interferences from TX to neighbour TVs and electronics equipment.

Vertical part L1 of the antenna is grounded that gives safety at the antenna operation. Figure 2 shows the schematic of the ATU. Coaxial cable (50- or 75-Ohm) with any length can go from TX to the ATU.

ATU should be preliminary tuned for each bands. Below described steps for the ATU tuning.

First step is: tune the circuit L1L2L3C2 to resonance at each working band when TX is disconnected from ATU. It made by a selection of the needed inductance of the inductor with help of a tap.

Figure 2 ATU for Antenna UB5UG

Plates of the capacitor C2 should be in the middle position. Then the proper tap is connected to the switch S1B.

First step may be done with help of a GDO or HF-Generator with HF-Voltmeter.

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