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%. In addition, the Thermaleze wire/Teflon tube windings on a large iron powder core allow the balun to handle large swings in impedance and high temperatures with ease.
All of these features make the unit very unique and rugged while literally providing the best of both a current and a voltage winding design when used with a balanced antenna. The Mod III is especially effective on the low bands and can provide enhanced matching capability where other baluns fall short.
If you use ladder line or twin lead for your antenna, this balun can be installed remotely allowing you to run a short length of coax into your tuner or transceiver. This type of installation will keep stray RF (common to ladder line) out of your shack while retaining the low loss efficiency of ladder line for your antenna. The model 4124x has no enclosure and makes a great balun for homebrew tuners or tuners that do not incorporate a 4:1 balun in their design.
Balun Designs offers 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 54MHz. Dr. Sevick's research showed that, when used with a balanced antenna, this balun provides current balance normally found only in a current winding. This design can be used with doublets, extended Zepps, large skyloops and is a good replacement balun for Super Loops.
Please review the impedance curves in the graph below to better understand the efficiency and response of this balun.
|Core Material|| Large 3" DOUBLE HEIGHT iron powder toroid for excellent low frequency performance.
Core is coated and sealed for long term durability.
|Winding Type|| Single bifilar wire pair wound as 4:1 tuner balun.
|Winding Material|| Heavy gauge polyamideimide Allex 240 Winding Wire.
Windings are inserted into Teflon tubes increasing total breakdown to 10,000 volts.
|Power Rating|| 1 to 35 MHz - 5kW, 7kW intermittent. 35 to 54 MHz - 4kW.
All ratings based on resonant load. High SWR will reduce power handling ability.
|Useable Frequency||1 to 45 MHz|
|Insertion Loss||Less than .02db|
|Connectors|| 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.
|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|
|Additional Info|| Very high efficiency (98-99%).
Iron powder core is very tolerant of high temperatures.