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New tool - toroidal ferrite core inductor calculator

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by SP3L, Jun 14, 2021.

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  1. KN5L

    KN5L Ham Member QRZ Page

  2. SV1IYF

    SV1IYF Ham Member QRZ Page

    Excellent graph, the HF droop has disappeared. Metal film resistor also noticed. The question now is whether under this calibration the self capacitance still remains in the decades of femtoF or has moved higher?
  3. KN5L

    KN5L Ham Member QRZ Page

    Which HF droop has disappeared?
  4. SV1IYF

    SV1IYF Ham Member QRZ Page

    That of the orange traces (real part of Z) of the previous two calibrations (#22 and #24 calibration wires) of the 3.3k resistor 15MHz and upwards.

    73 Nikos
  5. KN5L

    KN5L Ham Member QRZ Page

    The web page Orange trace is Series equivalent Rs. Rs value will be dependent on Q and capacitance. The two values which should be evaluated are parallel equivalent, Rp and Cp. Two different values resistors, with equal Lp, will have different Rs plots. This can be modeled in SimSmith:


    In the plot above, notice parallel equivalent C1Rp and C2RP are flat, same as in VNWA measurements. Where as, series equivalent C1Z.R and C2Z.R have same shape as in VNWA measurements.

    Has nothing to do with resistor type, only resistor value.

    John KN5L
    Last edited: Jul 12, 2021
  6. SV1IYF

    SV1IYF Ham Member QRZ Page

    Hi John,

    I have a problem adopting your final conclusion, that about the resistance value being solely responsible for the straightening of the orange trace. Three IMO important changes lie between these two orange traces, namely:
    1) More accurate calibration using a shorted (resistor shaped) jumper for the short calibration step, pre-compensating the 1.5k measurement geometry.
    2) Change of resistor type from carbon to metal film, admittedly faring better @hf.
    3) Change of nominal resistance value from 3.3k to. 1.1k.
    The possible interaction of the three may muddle which one is responsible for what. In similar cases the resolution of this problem is easy and straightforward: One change at a time.
    Last edited: Jul 13, 2021
  7. KN5L

    KN5L Ham Member QRZ Page

    Hi Nikos,

    Series equivalent resistance, Rs, trace is a function of resistance and can not be used to compare dissimilar resistance resistors.

    Added to:
    Are SimSmith models for all measurements to demonstrate difference between perfect model and measured parallel Rp and Series Rs traces. Also added a 1.5k Ohm Carbon film measurement.

    It is true that Metal Film are a litter flatter than Carbon Film at high frequency. Evaluate the two 1.5k Ohm "Meas Rp" traces to evaluate difference between two resistor types.

    John KN5L
  8. KN5L

    KN5L Ham Member QRZ Page

    I had a couple SimSmith images swapped. Carbon Film is preferred over Metal Film at high frequencies.

    John KN5L
  9. SV1IYF

    SV1IYF Ham Member QRZ Page

    Thanks John,

    I think I now understand why I couldn't follow you before. When you say Rp you mean shunt to bypolar input of your measuring device i.e. Center pin of port 1 to center pin of port 2. I understood R of a parallel equivalent circuit, which is seldom, if at all, used in amateur work. The mainstream equivalent circuit is the one the calculator returns which is kind of hybrid, that is the L component is represented by a serial cascade of a pure L and pure R, in parallel with a pure C assuming that the capacitor losses are neglible and hence a third parallel R representative of any C losses omitted. Now that, hopefully, I have sorted this out may I ask if in accordance with this equivalent circuit you still find the capacitance of the 10 turn 240-43 inductor around 70 femtoF?
    Last edited: Jul 13, 2021
  10. KN5L

    KN5L Ham Member QRZ Page

    Hi Nikos,

    As previously mentioned, 240-43 10T measurement was the result of several calibrations and measurements over a two day period. All measurements using same fixture. Any fixture changes will change the measurement.

    It is near impossible to measure a high inductance inductor at high frequency with any certainty.

    There are no validated (that I am aware of) processes to use Balun bench measurement to predict Antenna/Balun/TL/Ground common mode current.

    My suggestion for next steps is use a clamp-on current meter and perform some measurements. Example:

    John KN5L

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