On 10/28/20 8:14 AM, Jose Mihotek via groups.io wrote:
Roger & the group,
I stand corrected.The Z0 does change with freq.For coax, the change is small (<5%).For Ham purposes (HF), it is negligible.For VHF & UHF, if you use quality coax (Heliax), it is very negligible.For Microstip and Coplanar Waveguide, FR4 is a very poor choice. it is batch dependent. There is FR4 and there is? FR4...You should use Rogers4350B, it is much more stable and guaranteed.Alumina would be even better...
FR4 or XXXP is significantly cheaper than Rogers, though. There are plenty of applications where you just don't care. A microwave motion detector at 10GHz has short traces, and doesn't care what the loss happens to be.
