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K9AY loop antenna installed at PA6Z Contest group. This is a receiving antennas for the low bands (160m, 80m and 40m). Include schematics and info on a building the control box, preamplifier and low-pass filter

On 23cm the best way to obtain a good RX-sensitivity is to use a GaAs-FET in the front-end, since these devices show very low noise figures.

Wideband VHF/UHF/SHF monolithic PreAmp based on MARx-series by ON6MU

The W1TAG LF Receiving Loop is a specialized antenna project for LF reception, designed to mitigate local noise and enhance weak signal pickup on the lower frequencies. This square loop, measuring 6 feet per side, utilizes 14 turns of #12 THHN wire wound on a PVC frame, offering a robust mechanical structure. The design incorporates a series-tuned circuit with a coupling transformer, allowing for tuning from over 400 kHz down to _45 kHz_ using a switched capacitor bank. Construction details include the use of 1.5-inch PVC pipe for the frame, with specific measurements for spreaders and drilled holes for wire threading. The two 7-turn sections of wire are connected at the center, providing an option for a center tap. The loop rotates on a 1-inch steel pipe, enabling directional nulling of noise sources. The tuning unit, housed in a box clamped to the PVC, employs a 1:2 step-up transformer wound on an _FT-82-77 core_ and uses relays to switch capacitance values from 50 pF to 6400 pF, providing precise frequency adjustment. The current setup connects to the shack via 100 feet of RG-58, feeding into a W1VD-designed preamp, with plans for a balanced, shielded twisted pair cable upgrade.

VQLog 3.1 - 782 is a shareware logbook program designed for Windows operating systems (95, 98, NT, 2000, ME, XP, Vista, 7, 10, or later), supporting resolutions of 800x600 or higher. It can also operate on macOS and Linux via virtualization software like Virtual PC for MAC, Oracle VirtualBox, or VMware. The software facilitates QSO access by date, callsign, prefix, square, DXCC, and other parameters, offering robust import capabilities for ADIF, Cabrillo, and ASCII files from various contest and logbook programs. Key features include comprehensive award tracking for DXCC, WAZ, WAC, WPX, WAS, IOTA, TPEA, DIE, VUCC, 100EACW, and up to 30 user-defined awards. It generates customizable summaries and graphical statistics for QSO activity, DX contests, Most Wanted Squares (MWS), propagation openings, and prefixes. VQLog supports DX-Spot reception and processing from DX-Cluster and PSK-Reporter with programmable warnings, integrates with callbook services like QRZ.COM and Buckmaster's CD, and offers online lookup. Electronic QSL and log upload support extends to LoTW, eQSL.cc, Clublog, and DXMAPS, with real-time updates for online logs. The program provides extended QSO information for VHF-DXers, including separate TX/RX frequencies, start/end times, propagation modes, and specific entry fields for MS, EME, and Tropo. CAT support for rig control and interfaces with ARSWIN and PstRotator for azimuth/elevation control are also included.

A solutiom for the Ameritron AL-811(H) RF power amplifier, burnt panel meter lights. A common failure with the Ameritron AL-811 and similar amplifiers is that the panel meter lights burn out prematurely. These bulbs are usually integrated into the actual panel meter. The solution for this is to provide the meter backlighting with LEDs.

The WB5RVZ Genesis Radio G40 build log documents the construction of a 5W QRP 40m SDR transceiver kit, detailing each phase of assembly from power supply to RF filtering. It provides specific component lists, parts placement diagrams, and testing procedures for stages like the local oscillator, Tayloe detector, and RX op-amps. The resource highlights discrepancies between documentation versions and offers practical advice for builders, including a "virtual build" approach to preemptively address potential ambiguities in component identification and placement. It also addresses a specific "VK6IC Fix" for early board revisions, involving trace cuts and jumper wires for improved performance. The build log presents measured voltages and expected current consumption for various stages, such as the 4.9-5.0 Vdc on the 5V rail and under 100mA for RX current. It outlines critical adjustments like image rejection tuning, a common procedure for direct conversion receivers. The resource also includes practical tips for handling components like the 2N3866 transistor and its heatsink, emphasizing pre-assembly. It details the winding of two 1.45 uH toroidal inductors on T50-6 cores with 17 turns of #20 AWG wire, crucial for the RF path.

The Kenwood TS-870S HF transceiver features two state-of-the-art 24-bit 20 MIPS DSP chips, providing over 100dB out-of-passband attenuation and CW bandwidth adjustable to 50 Hz. It operates across 160-10 meters with 100 watts output, incorporating digital filtering, a beat canceller, and 100 memory channels. The radio also includes a transmit equalizer, RX antenna input, and a K1 Logic Keyer, enhancing signal processing and operational flexibility for amateur radio operators. Advanced capabilities include IF stage DSP, dual noise reduction, and an auto notch filter, all contributing to superior signal reception and clarity. The TS-870S offers a variable AGC, voice equalizer, and an RS-232C port for computer control, with Windows™ software supplied. Its built-in automatic antenna tuner functions on all bands for both transmit and receive modes, streamlining station setup and operation. Available accessories such as the DRU-3A digital recording unit, SO-2 high stability crystal oscillator, and VS-2 voice synthesizer option further extend the transceiver's utility. The unit requires 13.8 VDC at 20.5 Amps and is supplied with an MC-43S hand microphone, making it a comprehensive station component.

Designing and constructing a two-element receiving loop antenna array for HF operation involves specific considerations for achieving high directivity and noise reduction. This resource details a homebrew system comprising two 30-inch diamond-shaped loops, spaced 20 feet apart, which are fed through mast-mounted preamplifiers and passive signal combiners. The operational principle relies on adjusting phase delays between elements via precise _Belden 8241_ coaxial cable lengths, optimized for specific bands from 160m to 20m. Performance data, derived from _EZ-NEC_ modeling, illustrates consistent 90° azimuth-plane beamwidth and low take-off angles across the target bands, with _Receiving Directivity Factor_ (RDF) values comparable to a 300-foot Beverage antenna. The article presents detailed elevation and azimuth plots for 20m, 30m, 40m, 80m, and 160m, demonstrating the array's ability to provide strong response at low DX angles while also supporting _NVIS_ signals. Key components like the _DX Engineering RPA-1_ preamplifier and _DXE RSC-2_ signal combiner are discussed, alongside the importance of impedance matching to preserve antenna patterns. The construction emphasizes self-contained elements that do not require ground radials, offering a compact solution suitable for suburban environments and stealth installations, with a focus on optimizing receive performance independently from transmit antennas.

Developing operational amateur radio equipment for the 134 GHz band presents significant technical challenges, particularly in frequency generation and stability. This resource details the construction of a 134 GHz system, outlining its architecture with separate transmit (Tx) and receive (Rx) modules, each employing a local oscillator (LO) and RF head units. The system utilizes a dual Flann 50 GHz lens-type horn antenna configuration for optimal signal coupling. The transmit path incorporates an LMX2541 synthesizer chip operating at approximately 2.8 GHz, referenced by a 10 MHz double-oven Morion OCXO for exceptional stability. This signal is multiplied through a series of stages (X4, then X2) to generate a 22.4 GHz signal, which subsequently drives a dual series diode multiplier to produce the final X6 signal for 134 GHz operation. The receive side features an anti-parallel diode mixer coupled to a 144 MHz transceiver via a preamplifier, ensuring effective downconversion. Operational mode is CW, achieved by keying a multiplier stage. The project includes images of the Tx and Rx head units and describes a successful 3.5 km test with G8ACE, demonstrating stable signal tones due to PLLs locked to OCXOs at both ends, confirming the system's robust performance.

The _RTL-SDR V4_ dongle offers a tuning range from approximately 500 kHz to 1.7 GHz, encompassing HF, VHF, UHF, and microwave amateur allocations, with direct sampling improvements for HF reception. This guide outlines two primary installation methods for _OpenWebRX_ on a Raspberry Pi: utilizing an official Raspberry Pi image or employing a Docker installation. It also provides specific recommendations for Raspberry Pi models such as the 3/3B+, 4, and Zero 2 W, alongside practical advice for antenna selection and placement to optimize reception. _OpenWebRX_ is an open-source, browser-based SDR software package that facilitates web-accessible radio reception. The setup results in a receiver featuring a live waterfall display and demodulation capabilities for AM, FM, SSB, and CW modes. This configuration can be deployed for public access or restricted to a private network, depending on the operator's preference. Further sections address common troubleshooting scenarios and offer tips for mitigating noise, ensuring a stable and effective SDR listening station. The _RTL-SDR V4_ also integrates improved front-end filtering and a software-switchable bias tee, enhancing its utility for various amateur radio applications.

Analyzing 433 MHz radio signals from common wireless devices, such as temperature sensors and remote controls, involves understanding **On-Off Keying (OOK)** modulation. This resource details the process of capturing these signals using a Software Defined Radio (SDR) like Gqrx and then visually inspecting the captured audio data in a sound editor such as Audacity. It differentiates between **Pulse Width Modulation (PWM)** and Pulse Position Modulation (PPM) encoding schemes, illustrating how to identify and decode binary data by eye based on pulse and gap durations. The article provides a step-by-step walkthrough for decoding a wireless thermometer's data, correlating bit patterns with known temperature, humidity, and channel values. It also demonstrates decoding an RF remote control's button presses, highlighting the constant and varying parts of the transmitted packets. The content further introduces automated decoding using tools like RTL_433, explaining its capabilities in parsing various device protocols and showing how to interpret its output, including modulation type and decoded data. Specific examples include analyzing Prologue sensor protocol specifications from RTL_433's source code and noting common operating frequencies like 433.92 MHz in Europe and 915 MHz in the US.

Operating in a Single Operator Two Radios (SO2R) setup, especially with beverage antennas, often exposes the receiving radio's front-end to significant RF energy from the transmitting radio. This resource details a practical, homebrew receiver protection circuit designed to mitigate this risk. The core of the design involves a non-inductive 2W 22 Ohm carbon composition resistor in series with the RX antenna line, followed by two stacks of four fast-switching diodes (e.g., _1N914_) configured in opposite polarizations. This arrangement effectively clamps the incoming voltage to approximately 2.8 V peak-to-peak, safeguarding sensitive receiver input components. The series resistor plays a crucial role by absorbing excess power, preventing the diodes from exceeding their current ratings and potentially failing open, which would leave the receiver unprotected. The author, _N4KG_, measured up to 50 watts of coupled power between 80M slopers on the same tower, highlighting the necessity of such protection. The design is presented as a cost-effective solution to prevent damage to receiver input transformers, with the author noting successful protection of a receiver even after a resistor showed signs of overheating. This simple circuit can be integrated via a transverter plug, offering a robust defense against high RF input.

This document provides a comprehensive guide on purchasing high-frequency (HF) high-power amplifiers, discussing key considerations such as new versus used models, tube versus solid-state technology, and troubleshooting common issues. It emphasizes the importance of understanding power needs for activities like DX chasing and contesting, alongside practical tips for selecting and maintaining amplifiers to ensure reliability and performance in various conditions.

HamVNA presents an alternative Vector Network Analyzer (VNA) software tailored for the Hermes SDR RX/TX board, enhancing its utility for analyzing antenna systems and radio circuits. The software processes measurement data from two distinct sources: direct acquisition via the Hermes hardware, leveraging fixtures like Sam Wetterlin's Series Fixture or reflection bridge, or by importing existing TouchStone format files (*.s1p, *.s2p) from other VNA hardware. It operates on Win2000/WinXP/Vista/Win7 platforms, supporting both 32 and 64-bit architectures. The program incorporates standard Open-Short-Load calibration for reflection mode and Short Circuit calibration for transmission mode, with the capability to save and reload calibration data. A key distinguishing feature is its RLC Fit function, which automatically generates an equivalent RLC circuit matching the impedance-vs-frequency curve of the Device Under Test (DUT), a capability noted as unique among VNA software. This function allows control over circuit complexity via an 'Order' slider. HamVNA also supports remote calibration, enabling the removal of coaxial cable effects from measurements for clearer analysis, as demonstrated with an 80m vertical antenna example. The software is an open-source project, distributed under the MPL v.2.0 license, with both the installation package and source code available for download.

This resource provides a collection of modifications and repair procedures specifically for the _Yaesu FT-DX10_ HF transceiver. The database includes documented articles such as 'YAESU FTDX-10 blown USB Repaired Succesfully' and 'FT-dx10 RX Pre Amp dead'. Additional entries cover 'General Coverage Transmit on Yaesu FT-dx10' and 'Yaesu FT-DX10 mars tx expansion'. The platform also hosts user-contributed messages and comments related to these modifications, offering details on topics like amplifier control and solderless modifications. The content is structured to allow users to view all modifications for the _FT-DX10_ on a single page, facilitating access to technical adjustments and homebrew solutions for this specific radio model. The resource is intended for amateur radio operators seeking to perform hardware modifications or repairs on their _Yaesu FT-DX10_ transceivers.