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Phase
One practical use of the VNA phase measurement would be in adjusting the phase of the feeds to a multi-radiator antenna.
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A pair of stacked vertical dipoles can increase gain in the horizontal direction. If such an antenna is placed on a mountain top, it may be desirable to change the relative phase of the two dipoles to aim the pattern down toward the lower surrounding terrain. Measuring the phase of each splitter+cable feed can allow this to be properly set. --John Gord On Tue, Sep 24, 2024 at 04:12 PM, <avionicsfun@...> wrote:
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Also, the phase of the reflection coefficient (s11) and the phase of the impedance cross 0 at the resonant frequency of a resonant circuit. So looking at the phase trace gives a good way to measure the exact resonant frequency. This is useful to see the resonant point of an antenna or an LC trap.
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On Tue, Sep 24, 2024 at 04:12 PM, <avionicsfun@...> wrote:
The typical NanoVNA only measures the phase of the reflection coefficient (S11) which is NOT the same as impedance phase. Recent firmware from DiSlord also calculates the impedance phase angle and you can select it from the menu. Here is a plot of a 20 M antenna feedpoint showing the measurement of the two. Note how both cross at zero when the antenna is resonant. Roger |
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