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This web article by VK3BLG details the construction of an experimental 70cm (432 MHz) circularly polarized patch antenna, intended for satellite communication. The resource provides dimensions, feed point specifications, and impedance matching considerations for a single patch element, with discussion extending to array configurations for circular polarization. Construction involves a copper patch element on a dielectric substrate, fed via a coaxial cable. The design is based on information derived from AO-40 satellite antenna specifications, focusing on achieving circular polarization for satellite reception. The article includes specific dimensions for the patch and feed points, along with impedance values. Validation is implied through on-air satellite reception reports, with initial signal reports of **1 S-point above noise** for AO-40 beacons using a grid reflector, improving to **3-4 S-points above noise** with a 2-turn helical feed. The author references a _NanoVNA_ for impedance measurements and discusses the relationship between slot and dipole antennas in the context of patch design. DXZone Focus: Web Article | 70cm Patch Antenna | On-Air Satellite Reception | Circular Polarization

VE3NEA presents a detailed account of designing and constructing a **helical filter** specifically for 144 MHz satellite reception, addressing severe SDR receiver overloading from nearby Land Mobile Radio Network signals between 141 MHz and 143 MHz. The author's experience with RTL-SDR, RSP1a, and Airspy Mini receivers demonstrated the necessity of a narrowband solution to enable reception in the 145.8-146 MHz range with only 3 MHz separation from strong interference. The resource delves into the theoretical underpinnings of helical resonators, drawing upon Anatol I. Zverev's "Handbook of filter synthesis." It explains the equivalent circuit of a two-resonator passband filter, highlighting the critical role of stray capacitance (C3) in determining the coupling coefficient (K) and emphasizing the importance of **critical coupling** (K=1) for optimal filter performance. Misconceptions regarding tap positions and impedance transformation are clarified, with tap placement shown to control resonator loading and the trade-off between bandwidth and losses. Construction details include sourcing materials like 1/4" copper tubing and PCB, precise assembly techniques, and the use of tuning screws for frequency and coupling adjustments. Measurements performed with a NanoVNA revealed discrepancies from initial Coil64 calculations, necessitating adjustments to helix turns and tap positions to achieve the desired 3.5 dB passband loss and 40-50 dB suppression of interference.

This software connects to a NanoVNA and extracts the data for display on a computer, and for saving to Touchstone files.

The NanoVNA is a very compact handheld Vector Network Analyzer. The NanoVNA is tiny and portable analyzer, and it offers a high performance capabilities with an embedded lcd display.

QuickSmith provides an online _Smith chart_ for impedance matching, enabling users to drag virtual components onto a ladder network and observe dynamic trace movement. The tool displays live readouts for critical parameters such as VSWR, return loss, insertion loss, loaded Q, and bandwidth. It facilitates auto-matching to **50 ohms** with various network choices and supports _Touchstone_ file import, allowing _NanoVNA_ measurements to be plotted directly for analysis. Beyond basic matching, QuickSmith includes features for frequency and component sweeps, generating S11 and S21 response graphs. It also supports amplifier design, incorporating stability, gain, and noise circles, alongside microstrip and coax synthesis capabilities. The platform offers shareable links, worked examples, and guided tours, making it a practical resource for hams learning about RF circuit analysis and antenna optimization.

Very Tiny Palmtop Vector Network Analyzer by edy555. This is the original GitHub firmware repository implementing the standard 50KHz to 300MHz model

There are quite a few recipes for building a suitable transformer for an end fed half wave antenna (EFHW), but I was never sure I really understood the main principles. So, I wound a bunch of transformers, made measurements on them using my NanoVNA, learned how to get what I really wanted out of the VNA measurements, and in the process discovered how to build better transformers and be able to predict what they will do

The 1/4 wavelength vertical antenna project, initially designed for 20 meters, has evolved into a versatile portable solution covering 10 through 60 meters. K0BXB details its construction, emphasizing a bottom-loaded design with a tapped loading coil and four 10-foot counterpoise wires. The author shares personal experiences and field results, including **18 QSOs** during a park activation on 17m and 30m with 10 watts, and a **2,435-mile** contact with a contest station in Bonaire on 20m using 5 watts. Comparisons are drawn to commercial offerings like the _Wolf River Coils TIA_ and _QRPGuys Triband Vertical_, highlighting the DIY antenna's small footprint, light weight, and ease of tuning for POTA activations. The resource includes insights into using test equipment such as the _NanoVNA_ for SWR optimization and discusses various radiator lengths, from 17-foot wire to a 102-inch whip, demonstrating adaptability for different portable setups. Construction tips cover coil winding, tap placement, and connecting feedlines and radials using common components.

This project details the development of a modular direct conversion (DC) receiver designed for experimental flexibility in amateur radio and HF signal listening. The mainframe integrates a diplexer, DBM, and AF amplifier, supporting interchangeable local oscillator and antenna filtering setups. A tunable passive HF preselector complements QRP Labs bandpass filters for enhanced signal reception. Utilizing a NanoVNA for precise tuning, the receiver achieves improved signal-to-noise ratios across amateur and non-amateur bands, making it a versatile platform for further RF experimentation.

This report details a modification of a Diamond V2000 antenna, replacing its original two 0.50 m radials with two 1.55 m radials. Initial M5-threaded rods failed to fit; the housing required M6 threads. Custom radials were made using 8 mm OD aluminium tubing and M6-threaded stainless steel ends, secured with nuts machined to 9 mm. SWR issues on 6 m (>2:1) were largely due to a poor counterpoise connection, resolved during reassembly. NanoVNA measurements showed no adverse effects on 2 m or 70 cm. The final setup retains the two 1.55 m radials and original counterpoise. Other operators reported SWR degradation with similar mods—sometimes fixed by adding capacitance—but this was not observed here.

Facilitates interfacing with various NanoVNA models, including NanoVNA-H, NanoVNA-H4, NanoVNA-F, AVNA, and LiteVNA, to extract and display measurement data on a computer. The application supports splitting frequency ranges into multiple segments, increasing resolution beyond the standard 101 data points, with reported tests achieving up to 10,000 points for detailed analysis. Data averaging is also implemented to improve measurement accuracy, particularly beneficial at higher frequencies where noise can be more prevalent. Displays data across several chart types, such as Smith, LogMag, Phase, and VSWR charts, for both S11 and S21 parameters. Markers provide specific readouts for impedance, VSWR, Q factor, and equivalent capacitance or inductance at selected frequency points. Users can define and display customizable frequency bands as reference overlays on the charts. Developed in Python 3 (specifically >=3.10), the software leverages pyside6 for its graphical user interface, numpy for numerical operations, and scipy for scientific computing. This robust framework ensures stable performance and accurate data processing for amateur radio operators and electronics enthusiasts performing antenna and circuit characterization.

Presents a Windows software application specifically engineered to interface with NanoVNA vector network analyzers. The application's source code reveals modules like Calibration.cpp and GraphUnit.cpp, indicating robust functionalities for VNA calibration procedures and graphical visualization of RF measurement data. It supports various NanoVNA firmware versions, including NanoVNA H v1.2.24.dfu and NanoVNA H4 v1.2.24.dfu, ensuring broad compatibility across popular hardware iterations. Key components such as BatteryVoltageUnit.cpp, ColourPickerUnit.cpp, and SerialPort.cpp manage battery monitoring, user interface customization, and serial port communications, respectively. DataUnit.cpp handles measurement data processing, while SettingsUnit.cpp provides comprehensive control over application configurations, allowing hams to tailor the software to their specific analysis needs. The project integrates USB100.H and USBDI.H for direct USB connectivity and TCPIP.cpp for network-based communication, offering flexible options for connecting to NanoVNA devices. This software streamlines the process of analyzing and interpreting RF characteristics, making it a practical tool for antenna tuning and circuit analysis.