Model 4115ocf - 4:1 for OCF Dipoles 1.5 - 54 MHz 5kW

This design is built by winding individual cores as 1:1 choke baluns (100 ohm characteristic impedance) and then cross connecting them.  This creates a 4:1 current balun with excellent feedline isolation, very high RF choking and virtually perfect impedance transformation. A very good choice to build an Off Center Fed dipole around, but please note the caution statement below.

This model should NOT be used for a traditional Windom dipole that has a vertical coaxial radiator.  Instead, use the model 4125et to allow RF to pass to the vertical coax.

It should be noted that OCFD antennas were designed to provide low SWR for full power rating on even harmonics only, i.e. 80m, 40, 20m and 10m.  Use on WARC bands or 15m can create SWR greater than 2.5:1 which degrades the power handling of baluns by 60% or more.  Power on these bands should limited to a level not exceeding 500-700 watts ssb and 300-400 watts for FT8 or high duty cycle RTTY while on these odd harmonics.

If you look closely at the images, you can see the individually wound cores that form the balun. Each core has 10 individual turns to generate maximum choking impedance and produce near perfect transformation. The black polymer spacer is used to insure proper separation of the individually wound cores at all times. The balun includes the Top Eyebolt so you have a complete package for your antenna project. Please review the test scans below to appreciate the excellent specs this balun offers.

Click to Enlarge
   All testing done with an AIM-4170c Network Analyzer and precision 200 ohm load

  ***CAUTION*** 

If one or both legs of your OCF dipole will be installed over or close to (< 20 feet) your house, a large structure (garage, barn, etc) or near (< 30 feet) a metal roof/structure and you will be transmitting greater than 800 watts CCS,  DO NOT use this 4115ocf balun.  The interaction/coupling of the antenna with the structure and or metal will require high levels of common mode absorption by one ferrite core which will generate excessive heat in the core leading to a change in SWR and possible damage to the balun. Instead use our new Hybrid model 4116 which incorporates a 1:1 choke balun for higher feedline isolation and RF choking or the Model 4114ocf for legal limit power combined with a compromised installation and high power digital use.

There are a number of interesting designs for OCF dipoles available on our website 
listed under Antenna Design Links on the Support & Downloads tab at the top of the page. 

Specifications

Installation Notes