High Power 4/1 UNUN as “pre-match unit” for use with multiband monopole rod and wire verticals.

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 ON7FU 4/1 UNUN is built on a large ferrite torroid, using Teflon insulated wire for the windings.

In this way the UNUN can, with a conservative margin, withstand 1200 Watts PeP, even under mismatched conditions.

From August 1st 2018 on, all BALUNs are built into UL508A certified polycarbonate enclosures provided with flanges for convenient installation .

Specifications:

• Frequency range: 1,5 to 30 MHz
• Max Power:
  • 2400W PeP @  VSWR < 2,0/1 (ICAS) 
  • 1200 W PeP @ VSWR < 2,0/1 (CCS)
  • For ICAS and CCS power definitions, refer to “TECH INFO” tab.
  • 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 < 300 W PeP when VSWR is > 5/1.
• Insertion loss: < 0,1 dB 
• Intrinsic VSWR: < 1.3/1 at the frequency range edges.
• Stainless steel hardware.
• Splash Waterproof  with vent holes for moister control.
• Shock proof Polycarbonate housing
• Simple installation on the antenna support tube.

See also “General Conditions for Safe use of ON7FU Ferrite Applications products” under the tab “LEGAL INFO”.

Price: 146 Euro.

• Option N-connector (N-connector instead of SO239): + 7 Euro.