This simulation demonstrates how Localizer power, modulation, and phase effect the Localizer signal. Knobs and pots are based on the Mark 1 system. The blue rotary knobs do not function due to Flash Player emulation limitations.

However, SBO can be adusted with the "SBO Pwr" pot. SBO phase can be adjusted in fixed increments (30 or 90 degrees) using the radio (circle) buttons.

This is a great tool to visualize the relationship of power and width DDM at various observation points. Your observation point can be adjusted using the arrows above the Localizer radiation pattern.

The SBO Null can be shifted left or right of centerline by using the arrows below the Localizer Pattern. This effectively simulates trimming a left or right side feedline cable of an antenna pair. This is how you overcome an improperly aligned SBO null by adjusting the CSB modulation balance (Use Bal Cal or Mod Bal). This is known as deriving a centerline. Not ideal but it works. Especially during a flight check when there is no time to cut nulls in the antenna array.

Also, make note of the CSB (red) and SBO (green) vectors, and how they combine in space to create the composite vectors in blue. To see the green SBO vectors, you will need to move the observation point off of centerline (since you're in the SBO null). The 1/2 width point is also known as the course edge. It is where full scale deflection should occur on the aircraft ILS indicator. If you need help understanding vectors, I recommend checking out my video on YouTube here: Localizer RF Pattern Development.

Finally, apply 90 degrees of SBO phase with the radio buttons (either advanced or delayed) to see why 0.000 DDM occurs throughout the pattern in the quadrature condition (keep an eye on those blue vectors). We use this quadrature condition during system optimization to determine if the SBO is properly phased to the CSB. If so, any misphase condition from optimum will cause the system to go wide. We don't want misphase in the ILS because it requires more SBO power to achieve the same desired width.