I wonder how much this affects air dielectric coax (ie, solid copper tube coax) being as it has nothing but air between the center and screen ? .. the VF is normally 1 (or very close to) in air dielectric coax
when i saw the guts of the coax at the beginning of the video, i thought the VF variability is due to the core and skin effect... it looks like that coax is made of copper plated aluminum, so i thought it would make sense that at lower frequencies, lower skin effect, the aluminum core would slow the signal more than at higher frequencies, when the signal travels more in the copper layer.
I am a beginner in this subject, so please, no-one take my comment as fact, though I hope it is. Yes, permittivity, as expressed in the dielectric constant, does decrease in many/most materials as the frequency increases. One source said that inertia affects polarization - at high frequencies, the electron (ion, molecule- see edit below) has less time exposed to the force and thus moves less. Higher frequencies travel faster as the dielectric constant decreases with the frequency. Edited to add: Source: Prof. David R. Jackson, ECE 6340 Intermediate EM Waves Fall 2016 “At high frequency the molecules cannot respond to the field, so the relative permittivity due to the molecules tends to unity.“
I wonder how much this affects air dielectric coax (ie, solid copper tube coax) being as it has nothing but air between the center and screen ? .. the VF is normally 1 (or very close to) in air dielectric coax
You have a similar thing go on in capacitors; especially when used in switching regulators. 😊
when i saw the guts of the coax at the beginning of the video, i thought the VF variability is due to the core and skin effect... it looks like that coax is made of copper plated aluminum, so i thought it would make sense that at lower frequencies, lower skin effect, the aluminum core would slow the signal more than at higher frequencies, when the signal travels more in the copper layer.
I am a beginner in this subject, so please, no-one take my comment as fact, though I hope it is. Yes, permittivity, as expressed in the dielectric constant, does decrease in many/most materials as the frequency increases. One source said that inertia affects polarization - at high frequencies, the electron (ion, molecule- see edit below) has less time exposed to the force and thus moves less. Higher frequencies travel faster as the dielectric constant decreases with the frequency.
Edited to add:
Source: Prof. David R. Jackson, ECE 6340 Intermediate EM Waves Fall 2016
“At high frequency the molecules cannot respond to the field, so the relative permittivity due to the molecules tends to unity.“
Thank you :-)