Chapter 8

Demystifying Forward Gain vs Rearward Rejection

One of the most exciting things to hear is when a station reverses the directivity of a pair of phased verticals. The resulting difference in signal strength is astounding and suggests that the array exhibits an enormous amount of forward gain. But this is not the case.

As things turn out, a pair of phased verticals exhibits only 3 dB of forward gain and about 25 to 30+ dB of rearward rejection.¹ So when the array’s directivity is flipped, the huge difference is due to its rear null more than its forward gain. Although this may appear easy to understand, it can confuse people when heard demonstrated on-the-air.

In 2016, we documented this experiment in a YouTube video here.

K9RM in Indiana listens to the phased verticals on a remote receiver in the UK—which provides the audio heard throughout the video clip. When the phased verticals are pointed East and switched to their omnidirectional pattern, K9RM reports 5 dB difference. When the phased verticals are pointed to the West, and K9RM l…