Finally bit the bullet and ordered the HYS TC-YG08UV dual-band Yagi after reading good things about 9.5/11.5dBi gain figures. Got it mounted on a 20ft mast, but I'm seeing some strange behavior. SWR shows acceptable at 1.8:1 on 2m but jumps to 2.3:1 on 70cm when the boom is pointed north-south. When rotated 90 degrees east-west, both bands drop to under 1.5:1. Has anyone experienced directional SWR variation with these Chinese Yagis? The element mounting screws were indeed tough to tighten as advertised - took considerable effort but everything seems mechanically solid.

That sounds like a grounding issue or nearby conductor interaction. Try checking your coax routing and ensure the feedline drops vertically away from the antenna for at least one wavelength before any bends. Also verify all element connections are tight - I've seen Chinese Yagis ship with loose hardware.

Could be your mounting clamp affecting the pattern. If you're clamping around the boom near the driven element, try adding a non-conductive standoff or clamp further back toward the reflector. I had similar issues with my homebrew collinear.

Gamma match tuning on these imported Yagis can be finicky and sensitive to nearby objects. Any metalwork, guy wires, or other antennas in the near field? Even something 1/4 wave away can shift your impedance significantly on UHF.