[TowerTalk] Measure / Check phase difference between two antennas?

[Jim Brown]

On 3/12/2026 11:16 AM, Jim Lux wrote:
> The null depth will depend also on the relative gain of the two antennas.

In the world of pro audio, we learned that the frequency response of a 
system is complex -- that is, there are both amplitude and phase 
components, and that they are often of equal importance. For example, in 
the design of multi-way loudspeakers, where woofers crossover into 
mid-range devices and then into HF drivers. The positional relationships 
of the devices matter in the frequency range where they cross over, as 
does the complex response of the crossover circuitry, and it matters 
over the azimuth and elevation of listeners. The human ear does not like 
the variations in amplitude and phase that results from imperfections in 
the alignment of these devices, and the circuitry that feeds them.

Audio systems, which must cover 8 octaves of frequency, are far more 
complex than most RF systems, which rarely cover more than a small 
fraction of an octave.

I haven't investigated this with antennas, but intuitively, I suspect 
that the same can be true of many antennas, especially multi-element 
antennas, and their interaction with surrounding conductors, including 
the earth, also complex. One of the guys who taught us the most about 
this was the late Dick Heyser, whose day gig was space communications at 
JPL. Cancer took in early, in 1986.

73, Jim K9YC