Is a 1:1 vswr allways the lowest loss on a transmission line?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AI3V, Dec 13, 2019.

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  1. G8HUL

    G8HUL Ham Member QRZ Page

    Which of course is all smoke and mirrors, and breaks the first law of thermodynamics/conservation of energy. It only considers the impedance seen at each end of the line and totally neglects the fact that the transmission line has an impedance which remains constant, and a resistive loss which also remains constant. Both the incident and reflected wave are subjected to this loss.
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    1:1 is impossible. o_O
  3. AI3V

    AI3V Ham Member QRZ Page

    How exactly does minimizing current violate any law?

    Not that this curious effect dissapears after tge 1st quarter wavelength- due to the impedance transformation properties of any transmission line with a standing wave on it.

  4. AG6QR

    AG6QR Premium Subscriber QRZ Page

    That word "always" is a very strong word.

    True or false:
    True/false exam questions containing the word "always" are always false.
  5. KM3F

    KM3F Ham Member QRZ Page

    A 1.1 to 1 match on a matched line loss is different than a 1.1 to 1 match at a POINT along a mismatched line where the match is done with a tuner by transformation or line length selection.
    On a 50 ohm line terminated with a flat 50 ohm load only has the losses of the feedline and should result in very close to 50 +/- j 0. This is provided the test meter is accurate, the line is nominal 50 impedance and the test load is 50 non reactive ideal case.
    A 50 ohm line terminated in a mismatch has reflected power PLUS the same normal feedline losses adding up would result in 50 +/- j x value. This case provided the meter is accurate, the feedline may or may not be a different impedance and /or the load has an inductive or capacitance reactive value such as an antenna most likely would exhibit in reality.
    In a mismatch system all the power from the transmitter is accounted for.
    All the losses in the line are absorbed as heat at different points along the system. What is left is still radiated from the antenna.
    For example feed 100 watts to a system, 25 watts are lost in heat, 75 watts is still radiated.
    On the receiving end, that signal difference likely could not be perceived in either the S meter reading or the perceived loudness to any 'great' extent.
    Further the difference in db for the example is small when you consider a 3 db loss is a half power down and only about 1 S unit depending on the receiver calibration displaying it.
    I'm sure there are differences of opinion but it's the points being made overall.
  6. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

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