Zplots is a widely used, macro-enabled Excel application developed by Dan Maguire (AC6LA) designed to visualize, calculate, and analyze radio frequency (RF) transmission line performance. It works by importing raw impedance data from hardware devices like antenna analyzers or Vector Network Analyzers (VNAs) and translating that complex mathematical data into intuitive visual plots.
A core feature of the software is its dedicated “Measure Transmission Line Parameters” routine. 🛠️ How Zplots Measures Transmission Lines
To evaluate a physical cable’s performance, users typically run a process called an Open/Short measurement:
Gather Data: Connect one end of a transmission line to a VNA or analyzer. Leave the far end open and run a frequency sweep, saving the data as a Touchstone file (e.g., open.s1p). Short-circuit the far end and run the same sweep, saving it as another file (e.g., short.s1p).
Import to Zplots: Open the Zplots Excel sheet (with macros enabled), navigate to the Smith chart tab, and click “Measure TL Params”.
Analyze: Enter the physical length of the cable and upload the open and short files. Zplots uses complex number math to isolate the true physical characteristics of the cable across the swept frequency range. 📊 Key Performance Metrics Visualized
Once the raw frequency data is compiled, Zplots populates both XY linear charts and a digital Smith chart to track the following transmission line parameters:
Characteristic Impedance (Z₀): Plots the magnitude (|Z₀|), real part (R₀), and imaginary part (X₀) across the sweep to see how stable the line stays relative to its nominal rating (e.g., 50 or 75 ohms).
Matched Line Loss: Displays the true signal attenuation in multiple formats, including total loss over the entire line length, dB per 100 feet, dB per 100 meters, and S₂₁ insertion loss.
Velocity Factor (VF) & Delay: Visualizes the true velocity factor and precise time delay of the signal at every sampled frequency point.
Distributed RLGC Characteristics: Breaks down the line into its core distributed components, showing series resistance ®, series inductance (L), shunt conductance (G), and shunt capacitance © per unit foot or meter.
Impedance Transformations: Simulates the effects of adding or subtracting lengths of the transmission line to see how the complex impedance changes before reaching the transceiver or antenna. 💻 System Compatibility
Because it is powered entirely by Microsoft Excel charts and VBA code, Zplots does not require standalone software installation. It is highly compatible with data exports from popular amateur radio and RF test equipment, including RigExpert analyzers, AIM4170, and N2PK VNAs. Transmission line measurement with Zplots | RigExpert™
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