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This is another of Dr. Jerry Sevick's (W2FMI) most popular designs modified with various connector configurations. This model is much more than just high power. The specs are equivilant to the Model 1115u 5kw Isolation Balun but designed for easy installation with yagis, 1/2 wave dipoles or designs that work best with studs mounted on the sides of the enclosure. By using our mounting plate or mounting clamp, the balun mounts and works very well on masts or boom.
Specifications are very impressive. Using an AIM-4170 for testing, the balun shows an SWR below 1.06 across the HF band, literally flat transformation, and return loss that averages 60-75 dbmw. I will be glad to send the test results upon your request.
Additional Photos & Models:  
All of my baluns are hand made, hand wound one at a time utilizing the best available components for the power class. Any other balun of comparable quality will cost between $95 to $125 on the web. I am one of the few (if not the only one) that lets you see the internal structure before you buy. They may look simple but the right components are expensive and hard to find even before attempting to wind one.
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 of course, 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 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 is also reduced by eliminating EMI and other signal pickup by the coax shield.
Here are plots of the same dipole with and without a balun, notice how the pattern is distored 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 10,000 ohms creating very high voltages which can bring about voltage breakdown and/or excessive heating.
Also, please note that although this balun will tolerate very high SWR, efficiency drops markedly if your SWR is 4:1 or above.
Design features:
Utilizes specifications of Jerry Sevick, W2FMI, the authority on baluns. This is his Guanella current balun design which he modified to provide higher efficiency. By utilizing a new toroid mix, the bandwidth of his design has been increased.
Special mix toroid with low permeability allows broad frequency coverage. Toroid is coated with epoxy paint for added durablity.
This Isolation balun has significantly higher common-mode impedance and larger effective core area than other similar designs. It is much more effective than types with ferrite beads, ferrite bars or wound air-core coax.
Windings are Mil Spec 50 ohm coax rated 19kw @ 1mhz, 9kw @ 10 Mhz and 3.5kw @ 50 Mhz. Silver coated braid and silver plated, copper clad steel center conductor. Solid Teflon dielectric.
Typical insertion loss is less than 0.2 dB
Power handling of 5kw continuous - 10kw intermittent upto 35mhz. May be used to 50 mhz with slightly lower efficiency (1-2%) and power below 3.5kw continuous.
SO-239 connectors are silver plated with teflon insulation.
All hardware is stainless steel
N connectors and Alternate mounting options are available in Accessories.
Very high efficiency. Will not saturate like many of the typical cheap current baluns.
Balun is built installed in weatherproof 4" X 4" X 2" Nema Box which makes an excellent outdoor weatherproof enclosure.
This balun will handle continuous power of 5kw or 10kw intermittent and tolerate high SWR for extended periods.
It will not heat up at rated power, extended duty cycles or stressing load conditions.
You can see from the pictures there are three versions. One with closed eye loops to provide anchors for dipoles or with studs on the sides for mounting on a mast or other support. The balun can also be built with studs on top of the enclosure for use with yagis or applications that require this design. A closed loop in the accessories section can also be added to the top of the enclosure as a hanging support.
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