The Dark Side of the Conjugate Match

Discussion in 'General Technical Questions and Answers' started by KL7AJ, Mar 12, 2010.

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  1. W8JI

    W8JI Ham Member QRZ Page

    Source impedance has no effect on SWR measurement Pete.

    It doesn't matter if the source looks like one ohm or 1000 ohms, it will not change SWR ratio. Nothing we do with impedances on the input side of the bridge changes SWR.

    The exception would be if harmonics or spurious signals are generated, but that has nothing to do with changing the fundamental frequency SWR.

    For example an amplifier can generate harmonics that excite the line backward, and in that case the bridge can be sensitive to the termination on the exciter side of the bridge, but that has nothing to do with fundamental frequency SWR changes.

    Doesn't happen Pete, I can assure you of that!

    Take a clean transmitter, run it into a tuner, and then into the SWR meter and a load. No matter what we do with the tuner SWR will stay the same, with the sole exception of nonlinear changes in the SWR meter (meter error) slightly changing things as power level is varied.

    73 Tom
  2. K9AAN

    K9AAN XML Subscriber QRZ Page

    First, let me point out that photons cannot travel through wire. Therefore, only electric and magnetic fields need be considered when talking about transmission lines.

    At the risk of being ridiculed let me point out one place where I believe modern physics is in error. That is, RF energy, travelling in free space, is NOT composed of photons. Why: Photons are bundles of light. The energy of light is calculated differently than the energy in an RF wave. Light can be both particle and wave. RF is wave only.

    That light waves and RF waves behave the same does not make them the same. All waves behave the same irrespective of how they are generated or their medium of propagation or lack there of.

    It is my opinion that photons exist only when light behaves as a particle. When light behaves as a wave, it is a wave and not a photon.
  3. K9AAN

    K9AAN XML Subscriber QRZ Page

    OK. Let me get this straight.

    According to the original article [extremely well written, I may add, and admired], if we send the 100 watts down the transmission line and 60 watts are reflected, then 160 watts become the new forward power.

    BUT, the antenna reflects 60/100 of the forward power back. If the new forward power is now 160 watts, then the antenna now reflects 96 watts back.

    The 96 watts are now added to the forward power to make 196 watts of which about 118 watts are reflected. The 118 watts are now added to the forward power to make 218 watts of forward power...

    Or did I miss something?
  4. K9FON

    K9FON Guest

    lifes too short to fuss with conjugate matches, swrs, tuners and such. i just operate and have fun!:D
  5. AC0FP

    AC0FP Ham Member QRZ Page

    This is the way I've always seen things. Rf is a wave and photon's, well their kind of strange because they are mixture!


  6. WR9H

    WR9H Ham Member QRZ Page

    Hello Guys,

    RF and light BOTH have wave and photon (particle) characteristics and are really the same type of radiation. As the frequency of an RF emission is increased it behaves more like a particle (photon).

    This can be very confusing to grasp and it does help to go through a good physics textbook's electromagnetic emission chapter(s) to help with understanding.

    Ultimately radio waves are low frequency light and light is very, very, very high frequency radio!!

  7. VA3CQC

    VA3CQC Ham Member QRZ Page


    He's saying that it's a mathematical proof: the creation of a Conjugate Match doesn't in itself reduce the efficiency of your transmitter. SWR or no, it still delivers 100% power into the load, as long as a match exists (and is used, of course. lol @ 220w consumed / 75w produced under adverse condx).
  8. VK2TIL

    VK2TIL Ham Member QRZ Page

    Apropos 'UAQ's post (#29).

    Whilst the "downstream" impedance does not affect what happens "upstream", some kinds of measurements require that the entire system, from generator to load (DUT) be of a single Zo.

    If accurate vector measurements are to be taken, a single constant Zo, from signal-generator to DUT, is mandatory; for example, W7ZOI discusses return-loss bridges (in a manner that even I can understand) in "Introduction To RF Design" and shows that a Zo source is required for proper operation.

    Since a directional coupler is, essentially, a bridge, it seems to me that the same principles apply.

    SWR is a scalar measurement; it tells us a little, but not all, about the load.

    Measurements via a bridge or a directional coupler, if both magnitude & phase can be quantified, tell us much more.
  9. KA5S

    KA5S Ham Member QRZ Page

    Electrons travel -- slowly -- through wire. Photons (i.e. radio waves) don't; they are launched onto the transmission line. TL or space; makes no difference.

  10. KA5S

    KA5S Ham Member QRZ Page

    Dupe -- deleted. Off to thr swap meet!

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