Working frequency range of coaxial waveguide is limited by minimum wavelength λmin≈π*(D+d)/2. Where D is outer diameter, d is inner diameter. For wavelength<λmin, higher types of waves are excited in coaxial waveguide.
Its a big problem when using high power (> 50KW) TV transmitters ( Fc > 500 MHz). At a placed i worked at the older Txs had 6 1/8" feedery, the later generation had a lot of wave guide - It was HUGE ! (.9 X .6 m?)
Frank
on ebay I find two diameters, ones with 0.141'' and ones with 0.086''
Are they both suitable for 10GHz? (lengths less than 10cm)
Which of them are better for 10GHz?
Cable 0.141" has lower insertion loss than cable 0.086". But for lengths less than 10cm with connectors this difference is not significant, and cable 0.086" has lower bending radius for ease of installation.