UA6CA Multiband Windom Antenna for 80, 40, 20 and 10 Meters
Among the many wire antennas available to radio amateurs, the UA6CAWindom antenna remains one of the most practical solutions for operators seeking multiband HF coverage without complex matching networks or multiple antenna installations.
The design shown above is a variation of the classic Windom antenna, optimized by the Russian amateur radio operator UA6CA. It provides operation on the 80 meter antenna, 40 meter antenna, 20 meter antenna, and 10 meter antenna bands using a single horizontal wire and a carefully positioned off-center feed arrangement.
For operators with limited space and a desire for reliable performance, this multiband HF antenna offers an attractive combination of simplicity, efficiency, and wide frequency coverage.
The Windom UA6CA antenna is essentially an off center fed antenna measuring approximately 41 meters in total length. Unlike a conventional center-fed dipole, the feed point is intentionally displaced from the center. This creates impedance conditions that allow efficient operation on several amateur bands.
| Parameter | Value |
|---|---|
| Total antenna length | 41 meters |
| Short section | 13.6 meters |
| Long section | 27.4 meters |
| Antenna height | 20 meters |
| Ground wire length | 41 meters |
| Ground wire elevation | 0.2 to 0.3 meters |
| Ladder line impedance | 300–500 Ohms |
How the Windom Antenna Works
The original Windom concept uses an off-center feed point to excite multiple resonant modes along the wire. At different frequencies, the current and voltage distributions change across the antenna. Because the feed point is located away from the center, useful impedance values appear on several harmonic frequencies.
This characteristic allows the HF wire antenna to operate efficiently on:
- 80 meters (3.5 MHz)
- 40 meters (7 MHz)
- 20 meters (14 MHz)
- 10 meters (28 MHz)
The ladder line acts as a low-loss transmission line that transfers RF energy between the antenna and transmitter. Even when impedance mismatch exists, ladder line losses remain significantly lower than conventional.
Ground Wire
One unique aspect of the UA6CA antenna design is the parallel ground wire positioned approximately 0.2 to 0.3 meters above ground level.
This ground conductor performs several functions:
- Stabilizes antenna characteristics
- Provides a reference for RF currents
- Helps improve radiation efficiency
- Reduces unwanted feedline radiation
The ground wire should be installed directly below the horizontal radiator and maintain approximately the same overall length of 41 meters.
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