I have to utilize a VNA at work and while I'm understanding the theory better behind it, what I'm actually seeing when performing experiments doesn't match what I expect. As stated in the title, I'm using the Tektronix TTR506A VNA. I've calibrated it and I'm using a modified cal file. For example, I did an experiment with two antenna my company manufactures with differing bandwidth, the pictures are below. There are markers on at least one of the traces that show the bandwidth boundaries of the antenna. The final picture here shows the same results but with error correction on. The initial two images, error correction is off. I have each antenna hooked up to the VNA at the same time with a cable about 4 ft long. I found these antenna in a drawer (they're not brand new) and cannot say if they're damaged. But checking a second antenna that matches Antenna 1's product number, I get very similar results.
- On Port 1: 2.1 - 2.5 GHz 2.15 dBi Omnidirectional Spring Base Antenna
- On Port 2: 1.35 - 1.4 GHz 2.15 dBi Omnidirectional Gooseneck Antenna
- For S11 Log (yellow) there's a nice clean dip btwn the bandwidth markers. But then there's a dip immediately before the markers? And at around 5 GHZ, it looks sizeable
- For S22 Log (bright blue) there's a dip btwn the markers but then another one at around 4.5 GHz