Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AI3V, Dec 13, 2019.
Stay tuned for the answer !
(Here is a hint: the answer is no!)
The correct answer is also why ladder line has a lot less loss than coax.....it's not for the reasons normally given.
Are you gonna say it depends on which end you measure it at?
Absolutely! Have you ever seen a length of coax that's been operated with very high SWR with a lot of power? At every current loop, the coax is "dented."....where the dielectric melted because of the copper getting hot at those points.
Click here for a clue
Another neat trick is to build some ladder line out of very thin Nichrome wire (very lossy stuff). Run a few hundred watts into a dead short at the far end. The nichrome will glow red at the high current points, 1/2 wavelength apart.
Now what could you do (assuming equal power) to minimize current on a wire?
Raise the impedance of the load and increase voltage.
full explanation here
But here is the good part:
Note the red/black line.
Also note, that while the x axis is calibrated in feet, think in terms of wavelength. The actual line loss (3.2:1 vswr in this example) is less than the matched line loss for all transmission line lengths less than about 56 feet , or, 1/4 wavelengths! (Velocity factor corrected)
Like an ignition system in a car, very high voltage, high impedance transmission line and an even higher load impedance.
Even with mismatched impedances, the majority of power reaches the load. And that is with pulsed DC!