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Testing of real antennas is fundamental to antenna theory. The most common and desired measurements are the antenna radiation pattern including antenna gain and efficiency, the impedance or VSWR, the bandwidth, and the polarization. The procedures and equipment used in antenna measurements are described in this page.

The article explores the concepts of return loss, VSWR, and S11 within the context of microwave engineering, highlighting the confusion arising from their definitions. It clarifies that these parameters, while seemingly distinct, fundamentally describe the same phenomenon related to wave reflection and transmission in microwave circuits. The discussion emphasizes the historical context and mathematical relationships among these terms, revealing that their interpretation can vary significantly across different engineering disciplines. Ultimately, it advocates for a pragmatic approach to using these parameters based on familiarity rather than strict definitions.

Twenty 1-watt carbon film resistors are configured in parallel to construct a 50-ohm **dummy load** for amateur radio applications. The design incorporates a heatsink for thermal dissipation and an **SO-239 connector** for RF input, making it suitable for QRP operations. This budget-friendly project details component selection, soldering techniques, and mounting procedures, achieving a continuous power rating of 10 watts and intermittent handling of up to 100 watts across HF and VHF frequency ranges. The resource provides a step-by-step guide for assembly. This construction offers an economical solution for essential shack tasks such as antenna tuning, transmitter testing, and SWR meter calibration without radiating an RF signal. The utilization of readily available components significantly reduces the overall build cost compared to commercial alternatives, providing radio amateurs with a functional and reliable test accessory. While specific VSWR measurements are not provided, the design prioritizes practical utility for low-power transceiver diagnostics and general RF experimentation.

The FF-501DX LPF, a high-performance VHF and 10m filter, was obtained at a friend's SK sale. After becoming more active on 10m, the author reexamined the LPF and discovered it to be of high quality. The filter's efficiency was outstanding and the return loss/VSWR was better than estimated. The LPF was connected to a Bird 50R dummy load to evaluate insert loss, cutoff, attenuation over 70MHz, and return loss. The original specifications were found in an old radio magazine, along with a link to the original one-page information sheet. Comparing the results to the original specs confirms the LPF's quality.

Constructing a 4:1 Guanella current balun involves cross-connecting two 1:1 current baluns. At the low-impedance end, transmission lines from each balun are connected in parallel, while at the high-impedance end, they are connected in series. This configuration allows the device to achieve a 1:4 impedance ratio, effectively transforming a 200-ohm load to 50 ohms. The balun described utilizes **FT240-43 toroids** wound with 2.5mm2 twisted pair cable for 8 turns, intended for use with a 20m **Deltaloop antenna**. Measurements performed with a 200-ohm resistor demonstrate satisfactory VSWR and impedance characteristics across the HF bands. The article compares the performance of 2.5mm2 cable versus 1mm enameled wire, recommending the former for superior efficiency. Emphasis is placed on maintaining short core-terminal connections to optimize performance. Additional considerations include the option of integrating a separate Common Mode Choke (CMC) for enhanced common mode current suppression, especially if the balun's inherent suppression is not prioritized.

SAT filters ensure effective full-duplex satellite QSOs by mitigating interference between 145 MHz uplink and 435 MHz downlink signals. Custom coaxial and SMD-based filters address transmitter harmonic interference and improve receiver isolation, achieving over 70 dB suppression in the undesired band. Designed for simplicity, these filters maintain optimal VSWR and are housed in shielded brass enclosures. Practical implementations with Yagi antennas demonstrate compatibility with SDR systems, enabling seamless communication even in challenging satellite conditions, such as low-elevation passes and DX pile-ups.