This QRP balun is wound with mil spec teflon insulated coax which provides a consistant 50 impedance for the windings. The design provides high levels of feedline isolation, RF choking and excellent return loss for those who want top end performance in a compact, portable and light weight size. This balun is also available with 75 coax windings upon special request and at no additional charge.
This model is the popular Isolation/choke balun that is perfect for feedline isolation, noise reduction and RFI management. The model 1110w is great for quickly deploying a center fed monoband dipole or a monoband vertical.
Please review our Accessories Category for additional RF connector types and mounting options.
The enclosure for our low power units is small, lightweight and portable, but not intended for long term or permanent outdoor use. If used in a permanent outdoor installation, additional attention must be given to weatherproofing and strain relief. Damage caused by such use is not covered under our lifetime warranty.
Be sure to look at the unique mounts available for the QRP line of baluns
This is a current balun and has the widest operating frequency range, lowest core stress and provides the best overall balance of any balun for given cost, size, and weight. This balun is the best type to balance currents on each side of a 1/2 wave dipole or the driven element of a yagi while providing the perfect transition from a balanced antenna to unbalanced coax feedline.
Installing this balun will not affect antenna matching unless the feedline is acting as part of the antenna. This is, of course, not a desirable situation and installing this balun will correct the problem if one exists with the antenna. In beam installations, using a 1:1 balun in series with the antenna’s feed system can substantially improve the antenna’s front-to-back and front-to-side ratios. It does this by providing the antenna's driven elements with balanced current at the feedpoint and by preventing the feedline from acting as part of the antenna.
It is a seldom appreciated fact that feedlines, which are not adequately decoupled, can act as efficient vertical antennas degrading an otherwise excellent radiation pattern. The addition of a 1:1 balun can significantly reduce feedline radiation and dramatically decrease RFI and TVI. Beam antennas especially benefit from improved balanced drive and superior feedline isolation, but even simple dipoles benefit from properly selected and installed 1:1 current baluns. Receiver noise may also be reduced by eliminating signal pickup by the coax shield.
|Core Material|| Custom mix low permeability ferrite by Fair Rite Products for maximum bandwidth.
Core is coated and sealed for long term durability.
|Winding Type||Single core coaxial wound 1:1 current balun.|
|Winding Material||Mil Spec small gauge coax with Teflon dielectric, silver flashed braid and center conductor.|
|Power Rating|| 1.5 to 35 MHz - 300 watts, 35 to 54 MHz - 200 watts.
All ratings based on resonant load. High SWR will reduce power handling ability.
|Useable Frequency||1.5 to 54 MHz|
|Insertion Loss||Less than .02db|
|Connectors|| SO-239 connectors are silver plated with Teflon insulation.
Alternate connectors and Mounting Options are available in the Accessories section.
|Hardware||All Stainless Steel|
|Enclosure Type|| Polycarbonate (ABS) box with bottom plate that fits flush with the case
Plate is an exceptional fit that can be easily weatherproofed if desired.
|Dimensions|| Very compact and light weight 3x2x1.5 inch - Link to dimensional drawing
|Additional Info||Very high efficiency (98-99%).|
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.