Why VSWR value changing?

Hi everyone, last night i was testing my 145MHz Yagi antenna for VSWR value. I realized something stupid. When I was keeping the antenna close to ground, VSWR value was changing. Also, I stanted in front of the antenna same thing was happen. I search about that on internet but i am not be satisfied. If any one know the factors about this, please tell me. I will be really appriciated. Thanks a lot.

That nearby objects affect antenna tuning (and hence VSWR) is to be expected.

How much the tuning is affected depends on the objects and the distances involved.

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When the antenna touch or be near to the ground, there will be a parasitic capacitance in between. Thus the impedance of the antenna changed, so will be the VSWR reading.