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) works

As 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

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A knob that is 3 time the size of another equals a reduction of 3:1

S_O/S_I = d_O/d_I

Increase the speed the load moves with a Class 3 lever

Since the load or output length (d_O) 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 equation

The relationship between the effort speed and load speed is dependent on the ratio of the arms of the lever, according to the equation:

S_O/S_I = d_O/d_I

where

• S_O is the resulting speed of the output or load
• S_I is the speed of the input or effort
• d_O is the length of the output or load arm
• d_I is the length of the input or effort arm

Note that S_O/S_I 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.