2023-F-006 | 4/1 Unun for multiband monopole rod and wire verticals

Function

Trap- or coilless wire or rod antennas with a length varying from 6 to 14 meters are popular because of their simplicity. With some compromise, and a good antenna tuner, they can be deployed on multiple frequency bands.

The feedpoint impedance of such non-resonant vertical antenna is relatively random, causing high VSWR values. In order to bring the impedance within the range of a good external or built-in asymmetric antenna tuner, a 4/1 UNUN (Unbalanced to Unbalanced) impedance transformer is used, as a pre-match unit.

The UNUN assures reasonable low VSWR values on the coaxial feedline, avoiding excessive losses. As with any vertical, the efficiency and radiation pattern is largely depending on the radial field laid out below the antenna. This can vary from a simple grounding rod, in temporarily or emergency set-ups, to an extensive plane of radials in more permanent installations.

The UNUN can, with a conservative margin, withstand 1200 Watts PeP, even under mismatched conditions.

Mechanical Characteristics

• Optimized 61 mm diameter toroidal ferrites
• Heat resistant teflon coaxial cable with high breakdown voltage.
• Professional 50 Ohms N-connector or SO239 connector. (IP66 after sealing with self- vulcanizing tape or equivalent).
• Stainless steel M6 antenna connections. Stainless steel type 316 More info.
• Waterproof (IP64) and shock proof polycarbonate UV resistant enclosure. More info.
• Weight: +/- 500 g.

Electrical properties

• Impedance transformation ratio: 4/1
• Max. power:
• 2400 W PeP @ VSWR < 2.0/1 (ICAS)
• 1200 W PeP @ VSWR < 2.0/1 (CCS)
• For ICAS and CCS power definitions, More info
  
  
• Remark: For antenna VSWR values of > 2/1, some power de-rating has to be applied. As a rule of thumb, limit power to < 600 W PeP when VSWR is > 3/1 and limit to < 300 W Pep when VSWR is > 5/1.
• Deployable frequency range: 1.5 to 30 MHz.
• Insertion Loss: < 0.1 dB
• Intrinsic VSWR : < 1.3 / 1 at the frequency range edges.