TN-1 Enhancing Accuracy in Impedance Measurements Taken with the NanoVNA

This study examines accuracy limitations in impedance measurements performed using a NanoVNA. While the reflection method produces reliable results, the series-thru and shunt-thru methods introduce systematic errors, even when measuring standard calibration loads. To address these issues, improved calibration procedures incorporating additional measurements are proposed. By refining impedance conversion formulas, accuracy for the series-thru and shunt-thru methods is significantly enhanced, with results validated against reflection-method measurements. These refinements allow for more precise impedance characterization across a broader range of components. 

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TN-2 The NanoVNA Impedance Measurements in Practice

This technical note provides a practical guide to impedance measurements using the NanoVNA. It covers calibration procedures, measurement methods, and result processing for three impedance measurement techniques: reflection, series-thru, and shunt-thru. Each method is optimized for specific impedance ranges, and step-by-step instructions ensure accurate measurements. Practical considerations, including DUT connection techniques and data conversion using a dedicated Excel workbook, are discussed. The note emphasizes proper calibration and data handling to enhance measurement precision, making it a valuable reference for engineers and experimenters using the NanoVNA. 

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TN-3 Stray Capacitance Impact on Common-Mode Choke Measurements and How to Reduce It

This study examines how stray capacitance affects common-mode choke impedance measurements, leading to discrepancies between reflection and series-thru methods. Simulations confirm that stray capacitance shifts resonance frequencies, distorting results, especially when VNAs are connected to external devices. To mitigate this issue, a voltage transformer method is introduced, reducing stray capacitance influence and improving measurement accuracy. Practical implementation details and measurement validation using the NanoVNA are discussed, making this method a valuable tool for precise impedance characterization. 

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TN-4 Using the Voltage Transformer Method Calculator

This technical note introduces the Voltage Transformer Method Calculator, an Excel-based tool designed to simplify impedance calculations following vector network analyzer (VNA) measurements. The voltage transformer method, detailed in previous studies, requires complex computations that are automated within this workbook. The note provides step-by-step instructions for determining the transformer's Z-matrix parameters and measuring device impedance using input formats compatible with VNAs and antenna analyzers. Practical considerations, including measurement setup stability and data entry procedures, are covered to ensure accurate results. This resource aids engineers and experimenters in improving impedance measurement precision. 

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TN-5 Determining Complex Permeability of Ferrite Materials 

This study presents a practical method for measuring the complex permeability of ferrite toroidal cores, which is crucial for accurate impedance calculations in real, lossy inductors. Using a vector network analyzer (VNA), specifically the NanoVNA, permeability values are determined based on impedance measurements of a test coil wound on the core under examination. The document outlines the importance of selecting the appropriate number of turns to balance measurement accuracy and mitigate self-capacitance effects. Detailed procedures for test setup, data collection, and processing using an Excel-based calculator are provided, ensuring reliable permeability characterization. The study offers a systematic approach to verifying ferrite material properties, complementing manufacturer-provided data with direct measurements. 

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TN-6 Modeling Ferrite-Core Inductor

This study presents methods for modeling ferrite-core inductors, essential for understanding their behavior in antenna systems and circuit simulations. Traditional permeability-based models, while useful, fail to accurately represent self-capacitance effects. Measurements on a test inductor reveal discrepancies between predicted and actual impedance due to lossy capacitance. An improved model incorporating a lossy capacitor provides better agreement with experimental results. Additionally, alternative approaches using parallel RLC networks offer frequency-independent modeling suitable for circuit simulators. The findings guide engineers in selecting accurate inductor models for RF applications.

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TN-7 Using the Inductor Model Solver

This technical note explains the use of the Inductor Model Solver, an Excel-based tool for optimizing ferrite-core inductor models using impedance measurements. The workbook leverages Solver, a built-in Excel function, to calculate inductor parameters based on real-world data. The document provides step-by-step instructions for preparing measurement data, selecting the appropriate model (parallel RLC network or permeability-based), and refining results to achieve the best fit. Practical guidance on tuning initial parameters ensures accurate modeling, helping engineers and experimenters improve their understanding of ferrite-core inductors in RF applications. 

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TN-8 Measured vs. Specified Permeability

This study evaluates experimentally measured complex permeability values of ferrite materials, comparing them to nominal specifications provided by Fair-Rite for materials 31, 43, and 61. Measurements were conducted using multiple core sizes and processed according to established methodologies. The results reveal significant variability in both real and imaginary permeability components across frequency ranges, with measured values often deviating from catalog data. A comparative analysis quantifies these variations, highlighting their potential impact on balun and unun performance. Designers should account for permeability spread when engineering RF components to ensure consistency in practical applications.

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TN-9 Determining Complex Permittivity of Ferrite Materials

This study examines the complex permittivity of ferrite materials and its influence on inductors. Measurements on ferrite-core inductors show variations in capacitance and loss, confirming that ferrites exhibit unique dielectric properties. Using a NanoVNA-H4, ferrite toroids were tested in an air-gap capacitor, revealing frequency-dependent changes in permittivity. The findings highlight the need to consider dielectric losses alongside permeability losses when designing ferrite-core inductors for RF applications. 

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TN-10 Modeling Differential-Mode Behavior of Ferrite-Core Transformers

Accurate antenna system simulation necessitates comprehensive modeling of ferrite-core transformers, which often deviate significantly from ideal behavior. This technical note introduces methods for modeling the differential-mode behavior of such transformers. Two primary model classes are explored: equivalent-circuit models (including a transmission line model and RLC circuits) and the Z-matrix model. While equivalent-circuit models offer simplicity and ease of use in simulators like AutoEZ+EZNEC, the algebraically solved Z-matrix model provides superior accuracy, limited only by measurement precision. The document details the data collection process, requiring three test loads and six measurements, and highlights an Excel tool that streamlines the complex parameter-finding task for all described models.

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TN-11 Using the Differential-Mode Model Solver

This technical note provides a comprehensive guide for utilizing an Excel workbook designed to generate differential-mode models of ferrite-core transformers. It details the process of enabling and interacting with Excel's Solver Add-in to optimize model parameters based on measured impedance data. The document covers inputting various data formats, including S-parameters, and explains how to configure the solver for different equivalent circuit models (Transmission Line, Circuit A-E). Furthermore, it describes the direct calculation of Z-matrix model parameters and their application in analyzing device performance. This guide ensures users can effectively create and evaluate accurate transformer models for integration into antenna simulation packages like AutoEZ+EZNEC. 

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TN-12 Applying Ferrite-Core Transformer Models in AutoEZ+EZNEC

This technical note provides a practical guide for implementing ferrite-core transformer models within the AutoEZ+EZNEC software environment for antenna and matching network simulations. It details the integration of common-mode (Zcm) and differential-mode (DM) balun models, generated from external Excel tools and measurement data. The document illustrates how to incorporate various model types, including RLC equivalent circuits, transmission line models, and Z-matrix lookup tables, into AutoEZ's Insr Objs and Wires sheets. Examples demonstrate modeling a common-mode choke with a half-wave dipole, highlighting the importance of accurate common-mode and differential-mode characterization for precise antenna system analysis. This guide empowers users to enhance simulation fidelity by effectively leveraging detailed transformer models.

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SF-12 Supplementary Files Package for TN-12

Supplementary File Package for TN-12: Contains 9 AutoEZ-formatted models.

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TN-13 Capacitive Coupling in Antenna Matching Networks

This technical note explores the significant impact of undesired capacitive coupling on antenna matching network performance, presenting three distinct case studies. It demonstrates how such coupling, even between cascaded common-mode chokes or within a broadband matching network, can substantially alter common-mode impedance and affect differential-mode behavior. The document highlights that modeling based solely on individual component characteristics often diverges from real-world measurements. A key finding is that the proximity of a mast or boom, particularly with coaxial cable attached to it, drastically shifts the self-resonant frequency of a choke due to increased capacitance. The paper concludes with essential guidelines for antenna designers to mitigate these capacitive coupling effects for improved network performance.

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TN-14 Applying Ferrite-Core Transformer Models in SimNEC 

This technical note demonstrates the application of a ferrite-core transformer's differential-mode model within the SimNEC software. The document details how both Z-matrix and S-matrix based models can be implemented in SimNEC, using a common-mode choke connected to a dipole as an example. It explains the process of preparing the necessary data files (impedance and Touchstone) and presents simulation results for both matrix approaches, comparing them for accuracy and convenience. The note also highlights the capability of modeling the entire antenna directly in SimNEC, thereby reducing the need for multiple programs. 

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SF-14 Supplementary Files Package for TN-14

The package contains 11 files in reference to the TN-14.

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TN-15 Investigating Unexpected SWR Ripples on Multi-Vee Antenna Measurements

This technical note investigates unexpected SWR ripples observed during measurements of a Multi-Vee antenna, which deviated from initial simulator predictions. Initial troubleshooting, including antenna rotation and removal of nearby structures, yielded no explanation for the anomalous behavior. Subsequent modeling in SimNEC revealed that a slight discrepancy in the transmission line's characteristic impedance (53.5 ohms instead of 50 ohms) could reproduce the observed SWR ripple. This finding highlights how even minor impedance mismatches can significantly affect SWR plots, particularly for broadband antenna systems where such effects become more pronounced. The note concludes that accurate characterization of all system components, including the feed line, is crucial for reliable antenna performance prediction. 

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TN-16 Coaxial Feedline Lengths Causing Maximum Common-Mode Current

This technical note investigates how coaxial feedline lengths influence common-mode current excitation across various horizontally polarized symmetric antenna types, including half-wave dipoles, folded dipoles, and quad loops. Simulations revealed that the critical coax lengths leading to maximum common-mode currents are not universally fixed at multiples of a half-wavelength but vary significantly based on antenna type. A key finding was the surprisingly low common-mode current observed on the quad antenna's feedline, even at lengths problematic for dipoles. This suggests that the quad's closed-loop design may inherently contribute to lower common-mode currents, potentially explaining its historical reputation for quieter reception compared to open-ended antennas. 

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TN-17 Ferrite Core Impact on the Differential Mode Characteristics of a 1:1 Balun

This technical note investigates the impact of a ferrite core on the differential-mode characteristics of a 1:1 balun. Through comparative measurements, a balun constructed with a ferrite core was evaluated against the same length of coaxial cable alone. The results demonstrate that the differential-mode characteristics are determined solely by the coaxial cable's electrical parameters and length, indicating they are independent of the ferrite core's presence. 

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WB-1 Enhanced Converter of S-Parameters to Impedance

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WB-2 Voltage Transformer Method Calculator

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WB-3 Complex Permeability Calculator

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WB-4 Inductor Model Solver

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WB-5 Differential-Mode Model Solver

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