Model 1118d - 400 KHz - 2 MHz, 5kW - Optimized for LW Frequencies

$82.95
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1118d
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Balun Designs is pleased to offer a specialized 1:1 balun to compliment the new Long Wave frequencies.   The material utilized for the two stacked cores is optimized for the LW band and provides exceptional choking impedance at these frequencies.  An isolation/choking impedance in exess of 10,000 ohms is developed at 1 MHz. Note the cores used for this balun are intended for use on the LW band ONLY and will not provide high level choking or isolation at higher frequencies.

Please go to the Accessories category for additional RF connector types and mounting options.

Testing shows SWR remains below 1.05 across the entire LW band, transformation is perfectly flat, return loss is between 72-89 dbmw and choking impedance is maximized at over 10k ohms on the LW frequencies. Please click on the graphs shown below to view the complete test results.

model-1118-scan-thumb.jpg model-1118-choking-thumb.jpg 
Click to Enlarge

Tests run utilizing AIM-4170uhf Network Analyzer and a precision non-inductive 50 ohm load

 

 

 


Noise Reduction

While the most common advice is to improve the station's RF ground, the root of the problem is in the poor isolation of the feedline from antenna currents. If your goal is to reduce feedline radiation and improve reception by reducing noise, feedline isolation baluns are an excellent choice. Adding an additonal isolation balun at the point where the feedline exits the near field area of the antenna will substantially reduce unwanted feedline radiation and reception of EMI without the need for improved station grounding. 

Specifications



  Core Material   Custom mix ferrite by Fair Rite Products optimized for LW frequencies.
   Large 2.4 inch cores
  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
  Silver flashed braid and center conductor with solid Teflon dielectric.
  Power Rating   400 KHz - 2 MHz - 5kW
  All ratings at resonance. High SWR will reduce power handling ability.
  Useable Frequency   400 KHz - 2 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

 

Noise Reduction

It is a seldom appreciated fact that feedlines which are not adequately decoupled can act as efficient vertical antennas that degrade an otherwise excellent radiation pattern. The addition of a quality feedline isolation ("choke") balun can significantly reduce feedline radiation and dramatically decrease RFI and TVI. It does this by providing the antenna with balanced current at the feedpoint and by effectively preventing the coax shield from acting as part of the antenna.

While the most common advice is to improve the station's RF ground, the root of the problem is in the poor isolation of the feedline from antenna currents. If your goal is to reduce feedline radiation and improve reception by reducing noise, feedline isolation baluns are an excellent choice. Adding an additonal isolation balun at the point where the feedline exits the near field area of the antenna will substantially reduce unwanted feedline radiation and reception of EMI without the need for improved station grounding. 

If your antenna SWR is already low and you wish to reduce feedline radiation and improve reception, a feedline isolation balun is recommended. Adding one at the base of a vertical antenna will substantially reduce unwanted feedline radiation (RFI) by preventing your antenna from using the your coax feedline as a radial. This can also reduce the need for improved station grounding.


Benefits to Vertical Antennas

When quarter-wave antennas are constructed over a near perfect radial system, they have a feedpoint impedance of about 36 ohms. When they are constructed over a less than optimal radial-system there is a loss introduced into the feed system that adds to the 36-ohm figure. This improves the SWR but there is a loss in the efficiency of the antenna, signals transmitted and received have a higher take-off angle and often there is current introduced onto the feedline. 

With my SteppIR vertical I use two of these baluns. One at the base of the antenna and another midway along the feedline after the near field of the antenna. You can also install the balun where it enters your shack if you would rather not break the feedline run. The balun balances the RF currents at the antenna, is terrific for keeping RF out of your operating environment and greatly reduces the noise inherent in a vertical by decoupling the feedline. 

With a ground-mounted quarter-wave vertical, regardless of the radial situation, but especially with poor radial systems, there is the need for a feedline isolation balun to keep common mode currents off the feedline. 


Benefits to Yagis

Yagi antennas especially, benefit from improved balanced drive and superior feedline isolation, but even simple dipoles benefit from properly selected and installed Feedline Isolation baluns. In addition, receiver noise may also be reduced by eliminating stray EMI picked up by the coax shield.

Another very useful application for a feedline isolator is installing them in series with a yagi antenna’s normal feed system. The proper location is between the antenna’s matching device/system and the feedline. Doing this will not affect the antenna and prevents the feedline from acting as part of the antenna. In beam installations, using a feedline isolator in series with the antenna’s feed system can substantially improve the antenna’s front-to-back and front-to-side ratios.