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The article by Guy Olinger, K2AV, published in the May/June 2012 National Contest Journal, introduces the Folded Counterpoise (FCP), a compact 516-foot single-wire counterpoise elevated at 8 feet, designed for 160-meter operations on small lots like 100x150-foot backyards. Originating from efforts to revive Top Band for W0UCE on a postage-stamp property, the FCP uses strategic folds to cancel ground fields within 33 feet of center, minimizing losses to 0.13-0.53 dB—outperforming sparse or on-ground radials by up to 15 dB in poor soil—while mimicking opposed radials for efficient feedpoint impedance. Paired with a critical 1:1 or 4:1 isolation transformer (e.g., trifilar on T300-2 toroid) to block common-mode currents on coax feeds, it delivers proven results: K2AV's #8 North America low-power contest score, 7+ dB gains at W4KAZ and K5AF, and over 10,000 global web hits for DIY instructions using bare 12 AWG wire and weatherproof enclosures. Ideal for acreage-challenged hams, the FCP also excels on 80 meters with scaled dimensions, offering a low-loss alternative where full radials are impractical

Learn how to build your own RF signal generator for aligning radios by following the modifications made to the circuit of an existing project. Explore the use of a common cathode varactor diode and a single center-tapped 24 VAC transformer to simplify the design. Discover alternative components like the MACOM 4ST079CK-287T varactor diode, which offers cost-effective solutions compared to unobtainable options. Find inspiration in modifying existing projects and gaining practical knowledge in electronics. Purchase the Nuts and Volts magazine for detailed schematics and a deeper understanding of RF signal generators.

Integrating a _Software Defined Radio_ (SDR) into an existing ham radio setup involves connecting it with a standard transceiver (TRX), power amplifier (PA), and antennas. The core component is a splitter box that facilitates the connection between the TRX and the SDR, allowing for simultaneous operation without modifying existing equipment. In receive mode, the splitter ties the antenna inputs of both the TRX and a direct conversion receiver (DC RX) together. During transmission, the DC RX input is grounded via a fast telecom relay controlled by the transceiver's -SEND signal, incorporating a 10ms delay for safety. The splitter box includes a 3.7 dB input attenuator for impedance matching and acts as a protective fuse for the DC RX input. Ground loops are mitigated using common mode balun transformers, while the DC RX input is insulated with a broadband transformer. An audio switch box complements the setup, enabling users to listen to either the main transceiver, the SDR output, or both simultaneously. This configuration ensures noise immunity and safety, with the splitter housed in a screened box made from PCB material. On-air tests, such as the CQ WW 160m CW DX Contest, demonstrate the system's effectiveness, showcasing the SDR's ability to handle crowded band conditions with superior selectivity and dynamic range. The SDR's narrow bandwidth filters and waterfall display provide significant advantages, allowing operators to detect weak signals amidst strong interference. The integration of SDR with conventional radios offers enhanced operational flexibility and performance in challenging environments.

This comprehensive article dispels common misconceptions about Standing Wave Ratio (SWR) in amateur radio. The author explains that SWR is not an antenna property but a measure of the entire antenna system, representing the mismatch between transmission line and load impedance. Contrary to popular belief, modest SWR values (under 3:1) typically cause minimal power loss in HF applications. The article demonstrates mathematically why obsession with achieving 1:1 SWR is often unnecessary, explains when SWR matters more (QRO, QRP, VHF/UHF), and explores effective matching techniques including proper ATU placement and quarter-wavelength transformers.

This FAQ covers building and buying transformers for loop-on-ground and Beverage antennas. Building one uses ferrite cores and thin wire. Buying is an option, with the DX Engineering BFS-1 being recommended. These transformers isolate the antenna from the cable to prevent unwanted signal pickup.

This page by Arctic Peak provides a detailed explanation on how to use quarter-wave transmission lines as impedance transformers in ham radio antenna work. It explains how to match impedance values by connecting them with a λ/4 transmission line. The page also offers guidance on constructing your own transmission lines with specific impedance requirements, along with a calculator to determine the quarter wave length based on velocity factor and frequency. Useful for hams looking to optimize antenna performance and match transmission line impedance effectively.

Details the construction and performance of a phase-controlled receiving array, specifically a **MicroSWA** variant, optimized for QRP low band fox hunting on 40M and 80M. The resource documents the author's iterative design process, addressing significant regional noise challenges encountered during 0100-0230 UTC fox hunt periods. Initial experiments involved a director wire on a 40M vertical, yielding limited improvement, prompting a shift towards advanced null-steering techniques. The project leverages concepts from Victor Misek’s "The Beverage Antenna Handbook" and Dallas Lankford’s extensive work on phased receiving antennas for urban lots. A key modification involved integrating a new passive phase control box and a push-pull **Norton common base preamp** using 2N5109 transistors, designed for high third-order intercept performance to maintain weak signal integrity amidst strong adjacent signals. The system incorporates Faraday-shielded transformers with RG174 primaries on -75 ferrite cores, housed in ABS plastic pipe. Performance tests confirmed the MicroSWA's ability to produce deep, steerable nulls, achieving approximately 30 dB noise reduction on 160M, 80M, and 40M. This enabled detection of QRP signals undetectable on conventional transmit antennas. The final unit includes front panel controls, a 10-11 dB preamp, and a robust power conditioner, demonstrating effective noise mitigation for challenging low band QRP operations.

Demonstrates the construction of an active loop converter specifically designed for the Low Frequency (LF) bands, addressing common localized noise interference in LF reception. The design integrates a sharply tuned circuit and a tuned loop antenna, utilizing the loop as the sole tuned inductive element. By applying positive feedback, the converter significantly increases the loop's effective Q, achieving factors between 1000 and 2000, which sharpens tuning and reduces noise. The circuit employs an _NE602_ mixer stage, feeding its output to an HF receiver, with a crystal-locked local oscillator at 4 MHz. A 20-turn, 0.8-meter square loop antenna with 500 uH inductance is detailed, connected via 2 meters of figure 8 flex cable. The converter offers three selectable frequency bands: 195-490 kHz, 150-220 kHz (including the New Zealand amateur band), and 128-160 kHz (covering the European amateur band). Performance measurements indicate an effective 3dB bandwidth of approximately 100 to 200 hertz at 200 kHz. The article provides insights into component selection, including an _LF353_ op-amp and a trifilar wound transformer on a ferrite core. Sensitivity figures are presented, showing 7.5 uV of converted output per 1 uV/meter signal strength into a 50-ohm load, or 37.5 uV into an _FRG7_ receiver, highlighting its capability to extract weak signals from noise.