Nels, I should have said Hi-Z broadband transmission lines. Of course the tube amp situation is as Dave stated. I went to to calculate the spacing for the ladder line.
I was amazed at how rapidly it increases with the impedance. The line-to-line capacitance requirements just get really small. According to the equations presented,
300 Ohms --> 0.3 "
450 Ohms --> 1"
700 Ohms --> 8.5 "
1000 Ohms --> 105"
I'm very impressed with the nanoVNA, but with the 50 Ohm bridge design, I would not expect to achieve good accuracy at measuring at greater than 10 times the bridge Z, especially at higher frequencies.
