One of Dr. Jerry Sevick's (W2FMI) original designs. We have enhanced the original by using a weatherproof enclosure and various connector configurations that allow easy installation with any type of antenna.
Please review our Accessories Category for additional RF connector types and mounting options.
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.
Of course, this is 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 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.
Here are plots of the same dipole with and without a balun.
Notice how the pattern is distorted without the feedline being isolated by the balun:
*** 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 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 HALF WAVE CENTER FED DIPOLES WHEN USING A 1:1 BALUN AT THE FEEDPOINT.
|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, bifilar wire pair wound 1:1 current balun
| Winding Material
|| Heavy gauge Essex polyamideimide Allex 240 Winding Wire .
One strand covered with Polyimide tape to achieve 50 ohm characteristic impedance.
Breakdown voltage in excess of 7.5kv
| Power Rating
|| 1 to 35 MHz - 3kW, 35 to 54 MHz - 2kW.
All ratings CCW into resonant load.
|Useable Frequency|| 1 to 54 MHz
| Insertion Loss
|| Less than .02db
|| SO-239 connectors are silver plated with Teflon insulation.
Studs and eyebolts are 1/4 inch.
Alternate connectors and Mounting Options are available in the Accessories section.
||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.