How would you measure velocity factor of open wire feeders?

Chuck

Seems you would have to experiment to find the VoP of a given OWL. Every half wave the same set of conditions occur on a transmission line. Every 1/4 wave the opposite set of conditions occur. If you have a length of OWL and feed a signal on one end and had a RF volt meter connected on the same end you would read some RF voltage. Now, if you adjust the RF signal up and down the voltage will change. Your RF meter would have to be broad banded. The other end of the OWL is left open. When the adjusted frequency reaches a 1/4 wavelength the voltage will dip to a minimum. This occurs because a 1/4 wave down the line there is an open, so a short occurs at the voltmeter.

Now you know the frequency at which the piece of OWL is a 1/4 wave length. Now if you measure your length of OWL and compare that length with what a 1/4 wavelength (in space) is for the same frequency you will know the VoP for that OWL type. Divide the length of the OWL by the free space length (for a 1/4 wave length).

This is one way to do it, there may be other ways.

Fred