Balun Designs is now offering this unique balun using a three inch double height core. This larger size provides the necessary increase in inductance for enhanced performance on the low bands while maintaining the same wide bandwidth up through 50MHz. This new core also allows installation in our standard 4" NEMA box for ease of installation. This balun, when combined with a tuner, offers excellent broadband flexibility. If you use ladder line or twin lead for your antenna, this balun can be installed remotely allowing you to run coax to your tuner while keeping the efficiency and matching characteristics of the ladder feedline for your antenna. It also makes a great balun for homebrew tuners or tuners that do not incorporate a 4:1 balun in their design. This design is especially effective on the lower frequencies when used with long wires, large skyloops, inverted V's, Zepps etc. Jerry Sevick (W2FMI) specifically researched and designed this balun to provide a very constant 50 ohm input impedance on the lower frequencies where most baluns can drop by 20-40%. Please review the impedance curves in the graph so you can see the efficiency and response of this balun. The Mod III is especially effective on the low bands and can provide enhanced matching capability where other baluns fall short.   Additional Photos & Graph:   Design Features: Toroid with a low 10 permability that allows broad frequency coverage. This is a large 3" DOUBLE HEIGHT iron powder toroid that provides excellent low band impedance matching. Toroid is also coated with epoxy paint for added durablity. The large toroid provides better inductive reactance for excellent low frequency response. This makes the balun very efficient on 160, 80 & 40 meters while maintaining excellent performance for higher frequency multiband designs. Input impedance remains basically flat across the full HF spectrum well past 30 Mhz (see graph below). Competing designs can very as much as 40% especially from 1-5 Mhz. 2 separate bifilar windings of 14 guage Thermaleze wire inside Teflon tubes. Minimum of 10,000v breakdown voltage. SO-239 connector is silver plated with teflon insulation. All hardware is Stainless Steel. N connector and Alternate mounting options are available in Accessories. Because of the high efficiency and size, it will not saturate like the smaller toroids or small stacked baluns used in many tuners. Iron powder core is very tolerant of higher temperatures. Balun is built installed in 4" X 4" X 2" NEMA Box which makes an excellent outdoor weatherproof enclosure and can be easily mounted remotely.   This balun is also available without the enclosure for installation in your antenna tuner.   This balun will handle continuous power of 4kw and tolerate high SWR for extended periods. It will not heat up at rated power, using extended duty cycles or stressing load conditions.