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Thread: RigExpert AA-55 Zoom Antenna Analyser (Series/Parallel Mode)??

  1. #1

    Default RigExpert AA-55 Zoom Antenna Analyser (Series/Parallel Mode)??

    Hi All,

    I have recently purchased a new AA-55 Analyser in an effort to improve and better understand my Transmission Line & Antenna combination.

    I have a number of questions but I will start with this one:

    In the data screen

    Data Screen.jpg

    It shows either a Series or Parallel Mode.

    Why have the two as I would have thought most antennas would be Series??

    Pete VK4CCV

  2. #2


    An example of parallel use might be a hairpin or coax stub measurement. The rigexpert website suggests that these analyzers are also useful for component testing.

    An excerpt from

    "Since the impedance measuring instrument is unable to determine the measurement target’s circuit mode, it is necessary to select the correct equivalent circuit mode in order to reduce error. Generally speaking, series equivalent circuit mode is used when measuring low-impedance elements (approximately 100 Ω or less) such as high-capacitance capacitors and low-impedance components, while parallel equivalent circuit mode is used when measuring high-impedance elements (approximately 10 kΩ or greater) such as low-capacitance capacitors and high-impedance components."

    Information from another source
    makes similar statements:

    "If one is trying to determine the DC value of a resistor using AC measurements it is best to make series measurements of low-valued resistors (say under 1k) and to make parallel measurements of high valued ones. In most cases this almost completely avoids errors due to series inductance and parallel lumped capacitance. Also, a low frequency should be used. Note that sometimes an AC measurement can give the correct DC value better than a DC measurement because thermal voltage and drift errors are avoided and measurement sensitivity is apt to be higher. Other cases where parallel measurements are preferred are when measuring very low values of capacitance, when making measurements on dielectric and magnetic materials, and, of course, when trying to determine the separate values of two components in parallel."

    I also recall from reading the manual of an unknown analyzer long ago that the mode which varies least in component values as the frequency is changed is the more accurate measurement. I would have assumed that my rigexpert simply "did the math" to determine the parallel equivalent using the series values, but comparing the modes using a single resistor with the shortest leads possible across the port seemed to give different results. I probably need to calibrate mine.

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