Per the image below, I've just re-calibrated and then connected my NanoVNA to analyze the SWR of a 1/4 wave antenna tuned for 70cm. The horizontal axis is 100mhz - 500mhz. Why would the resulting graph have these small recurring waves within the larger (and understandable to me) trend of an SWR decrease with increasing frequency? I've seen this before, though rarely, while using the NanoVNA but I have never seen this amount of deviation from the larger trend line. Would it make sense for a 1/4 wave 70cm antenna to exhibit this fluctuating high and low SWR? Or is this indicative of some error in my measurement method?