Most high efficiency mobile HF antennas also present impedances lower than 50 ohms at the feedpoint on some bands. Even a full size quarterwave vertical near the ground will have a feedpoint impedance that is a bit low for good direct matching with 50 ohm coax. This design works on both balanced antennas (such as the excellent Buddipole (tm) portable lightweight dipole, or low wire NVIS dipoles) as well as verticals (such as the Buddistick (tm) configuration of the Buddipole (tm) Antenna System). This can be especially troublesome in portable work where the coax is very short and the antenna very close to the transceiver. In addition, it is desirable to choke off any imbalance current and avoid RF on the chassis of the transceiver which results in many problems. Due to varying conditions and configurations the impedance may vary considerably and more than one impedance ratio may be necessary to obtain an adequately low standing wave ratio (SWR) to the transceiver. Even fullsize dipoles close to the ground have low feedpoint impedances. This usually results in low feedpoint impedances. They are often loaded with inductors to make up for less than full length elements, and may be operated close to the ground. Portable Antennas need to be small and light. Even though the antenna is RESONANT, they often present an impedance other than 50 ohms to the feedline. There are a number of possible causes for this, and the major one is IMPEDANCE The SWR would drop tantalizingly down and then rise back up as it was adjusted? Have you had an antenna that, no matter how you adjusted or trimmed it, would not get below 1.5:1 (or perhaps even 2:1 or 3:1) Standing Wave Ratio (SWR)? Testing the TRB (Triple Ratio Balun) with the Autek RX Vector Analystĭocument Ver 1.38 Kits available now from our
WB6ZQZ 3 in 1 Balun WB6ZQZ Triple Ratio Balun
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