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Balun Designs

Model 1115 - 1:1 Balun, 1.5-54 MHz, 5kW


Model 1115 - 1:1 Balun, 1.5-54 MHz, 5kW

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Product Description

Balun Designs in collaboration Fair Rite products has developed what we consider to be the best single core 1:1 feedline isolation balun available today. By reviewing the scans shown below you can see what we're referring to.  Notice how the level of choking impedance ramps up very quickly developing 3100 ohms on 160m and continues at even higher levels across the full HF spectrum. This is a very difficult level to achieve and maintain for a single core balun and is truly exceptional. Whats more, the transformation, SWR and return loss are excellent. This balun is unique in the marketplace today.

Windings of Mil Spec coax allows this balun to provide a very high power rating across all HF frequencies with windings that have extremely uniform impedance for excellent transformation and very good choking impedance. By utilizing one of our mounts in Accessories, the balun can be securely installed on a mast, boom or where ever you need it. 

Sometimes called a choke balun or common mode choke, this 1:1 ratio current balun is the best for feedline isolation. It has the widest operating frequency range, lowest core stress and provides the best overall balance of any balun for given cost, size, and weight. If you have a yagi you should be using one to balance the power to the driven elements and prevent the coax feedline from distorting your radiated pattern. If you have a vertical you should be using one to prevent the vertical element from using your coax as a radial and to decouple the feedline for reduced noise.

Please review our Accessories Category for additional RF connector types and mounting options.

This balun is more than just high power. Tests show SWR is below 1.04 across the entire HF band, transformation is perfectly flat, return loss is typically 65-85 dbmw. Please click on the graphs shown below to view the complete test results.

new-1115-scan-thumb.jpg new-1115-choking-thumb.jpg 
Tests completed utilizing AIM-4170c Network Analyzer and precision 50 ohm non inductive load.

Tests carried out in an anechoic chamber to determine the affects of unbalance on radiation patterns of a half wave dipole (published April, 1980 in QST) show just how serious this can be and how important the function of the balun is in achieving predictable patterns. Notice how the pattern is distorted when the feedline is not being isolated with a balun.

Click to Enlarge

Regardless of the antenna you're using, an isolation balun can provide numerous advantages:

   Preventing unwanted RFI by eliminating feedline common mode currents and radiation.
All power goes to the antenna, improving efficiency.
Power is balanced between driven elements of antenna.
   Can help overcome a less than optimal ground.

!!! One Exception !!!

It must be pointed out that a 1:1 balun should never be used on the second harmonic of a half-wave center-fed dipole fed with coax (like an 80 meter dipole being used on 40 meters). The impedance can be 5000 ohms or greater creating very high voltages which can bring about voltage breakdown and/or excessive heating. This exception ONLY applies to HALF WAVE CENTER FED DIPOLES WHEN USING A 1:1 BALUN AT THE FEEDPOINT and does not apply to dipoles fed with ladder line.


 Core Material  Custom mix low permeability ferrite by Fair Rite Products for maximum bandwidth.
  Large 2.4 inch core is coated and sealed for long term durability.
 Winding Type  Single core, coaxial wound 1:1 current balun
 Winding Material  Mil Spec 50 ohm coax rated 19kW @ 1MHz, 9kW @ 10 Mhz and 4kW @50MHz. 
 Silver flashed braid and center conductor with solid Teflon dielectric.
 Power Rating  1 to 35 MHz - 5kW, 35 to 54 MHz - 4kW, 5kW intermittent
  All ratings CCW into resonant antenna.
 Useable Frequency  1.5 to 54 MHz
 Insertion Loss  Less than .02db
 Connectors  SO-239 connectors are gold center conductor with Teflon insulation.
 Studs and eyebolts are 1/4 inch.
 Alternate connectors and Mounting Options are available in the Accessories section.
 Hardware  All Stainless Steel
 Enclosure Type  NEMA rated 4x marine grade junction box for outdoor installations.
 Cover has neoprene gasket for weatherproof integrity.
 Dimensions  4x4x2 inches for main body of unit
 Dimensional Drawing of Standard Enclosure
 Additional Info  Very high efficiency. 
 Will not heat up or saturate at like many of the "less expensive" designs.

Installation Notes


Additional Information