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Balun Designs

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


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

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Product Description

Designed for those who want the maximum isolation and choking across the full HF spectrum. Building on the original 1:1 design by Dr. Jerry Sevick, this balun has two (2) cores in a stacked configuration to maximize choking impedance on HF bands from 1- 54MHz. By utilizing Mil-Spec coax, the SWR, Transformation and power handling are excellent while providing a choking impedance that exceeds 10,000 ohms. Even on 80m the choking impedance is over 2,000 ohms.  If you have RFI primarily from the lower frequencies or operate more on the low bands (160 thru 40m) you should consider the model 1116d for enhanced suppression and isolation on these bands.

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

Sometimes called a choke balun or common mode choke, this 1:1 ratio current balun is the best for feedline isolation and choking. 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. Please click on the graph shown below to see the complete results.

model-1115d-choking-thumb.jpg  model-1115d-thumb.jpg
Click to Enlarge
Tests performed with AIM-4170c Network Analyzer and precision 50 ohm non inductive load.


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

    • Prevents unwanted RFI by eliminating feedline common mode currents and radiation
    • All power goes to the antenna, improving efficiency
    • Reduces noise or EMI picked-up by your coax shield
    • Power is balanced between driven elements of antenna
    • Can help overcome a less than optimal ground


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 as great as 5,000 ohms creating very high voltages which can bring about voltage breakdown and/or excessive heating. This exception ONLY applies to Coax Fed HALF WAVE CENTER FED DIPOLES WHEN USING A 1:1 BALUN AT THE FEEDPOINT.  This caution does not apply to fan dipoles, doublets fed with ladder line or any dipole that utilize loading coils to create resonance on the bands in use.




 Core Material  Custom mix low permeability ferrite by Fair Rite Products for maximum bandwidth.
  Large 2.4 inch cores are coated and sealed for long term durability.
 Winding Type   Stacked dual core, coaxial wound 1:1 current balun provides larger effective core area.
 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, 10kW intermittent. 35 to 54 MHz - 5kW.  
 All ratings at resonance. High SWR will reduce power handling ability.
 Useable Frequency  1 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 utilizes integral 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