The SR-705 (Speed Reduction) knob makes tuning easier for magnetic loop antenna.The SR-705 has been designed in Autodesk‘s Fusion 360 by our engineers and takes 3 1/2 hours for our equipment to build. Each thermoplastic polyester unit is then finished off by hand to fit on any round 1/4 inch nylon shaft. This provides a perfect fit for the Icom AL705 antenna.How the SR-705 (Speed reduction knob) worksAs you will see below, a lever that is made 3 times the size of a standard knob is the same as having a 6:1 reduction drive installed on a variable air capacitor with a 360 degree turning radius.As an added benefit, the silver rod can be positioned to point left when the loop is tuned for 10 meters and right when tuned for 40 meters.A 180 degree turn with a reduction of 3:1 = a 360 degree turn with a reduction of 6:1 180/3 = 360/6 or 60/1 = 60/1 or 6:1–A knob that is 3 time the size of another equals a reduction of 3:1SO/SI = dO/dIIncrease the speed the load moves with a Class 3 leverSince the load or output length (dO) is longer for a given lever length, the Class 3 lever would result in a greater speed mechanical advantage and be able to project the object faster.Speed equationThe relationship between the effort speed and load speed is dependent on the ratio of the arms of the lever, according to the equation:SO/SI = dO/dIwhere SO is the resulting speed of the output or load SI is the speed of the input or effort dO is the length of the output or load arm dI is the length of the input or effort armNote that SO/SI is the speed mechanical advantage of the lever.Example: As the AL-705 uses a variable air capacitor with a 180 degree turn, using the 3:1 reduction offered from our SR-705, provides you the equivalent of a 6:1 reduction on a 360 degree turn.Specifications, prices, and descriptions are subject to change without notice.Reviews5.0 Based on 6 reviews5 star100100%4 star0%3 star0%2 star0%1 star0% Search1-5 of 6 reviewsMost RecentMost Helpful Protected_User_8a5fcee3 Verified owner December 22, 2025 SR-705 (Speed Reduction) knobVerified review - view original Protected_User_e3dc68e0 Verified owner October 12, 2025 SR-705 (Speed Reduction) knobVerified review - view originalThis ingenious speed reduction knob installs easily and allows fine tuning of my Alpha Antenna Mag Loop. Protected_User_a48c5dae Verified owner September 19, 2025 SR-705 (Speed Reduction) knobVerified review - view originalI recently read a magazine article mentioning the use of the Alpha SR-705 knob and quickly ordered it for my Alpha Loop, Jr. It arrived in a couple days and I easily installed it in minutes. It’s amazing how little effort it now takes to precisely tune a loop antenna. Thanks Alpha Antenna for providing this needed accessory. Protected_User_fd51bf2e Verified owner September 17, 2025 SR-705 (Speed Reduction) knobVerified review - view originalGreat improvement over the standard tuning knob Protected_User_53b1dc90 Verified owner October 6, 2023 SR-705 (Speed Reduction) knobVerified review - view originalMakes tuning your magnetic loop quite a bit easier Show more reviews (1)Sorry, no reviews match your current selections
