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Author evaluated a custom-built passive AM loop antenna, achieving notable DX reception including KLBJ Austin (230 miles) and WWL New Orleans (700 miles). The antenna operates solely on resonant inductive coupling, enhancing weak signal reception without external amplification. This project illustrates how fundamental RF design—calculating inductance, capacitance, and Q factor—can significantly boost performance of consumer-grade radios. Detailed construction techniques, theoretical background, and optimization strategies for effective loop antenna design are presented for amateur and experimental use.

FFTDSP is a PC program which can detect weak radio signals in real time. Uses the PC's soundcard and advanced signal processing techniques, extracts and displays weak signals from the receiver audio.

Winrad is a free software program designed to implement a Software Defined Radio (SDR), meant to run under Windows XP, Windows 2000, or Windows 98SE. In a nutshell, it accepts a chunk of up to 96 kHz coming from a complex mixer in form of two signals, I and Q, fed to the PC sound card.

A software defined radio by Alberto I2PHD

The DSP-10 is an amateur-radio, software-defined 2-meter transceiver that can be built at home. It operates not only on SSB, FM and CW, but also on four Weak-Signal modes. Features are tailored to operation on VHF, UHF and Microwave frequencies. By W7PUA

WSJT-X implements communication protocols including FST4, FST4W, FT4, FT8, JT4, JT9, JT65, Q65, MSK144, WSPR, and Echo. These modes facilitate reliable, confirmed QSOs under extreme weak-signal conditions. JT4, JT9, and JT65 utilize a nearly identical message structure and source encoding, employing timed **60-second** transmit/receive sequences synchronized with UTC. JT4 and JT65 are designed for EME on VHF/UHF/microwave bands, while JT9 is optimized for MF and HF, offering **2 dB** greater sensitivity than JT65 with less than 10% of its bandwidth. Q65 provides submodes with varying T/R sequence lengths and tone spacings, suitable for EME, ionospheric scatter, and weak signal operations on VHF, UHF, and microwave. FT4 and FT8 operate with T/R cycles of 7.5 and 15 seconds, respectively, supporting enhanced message formats for nonstandard callsigns and contest operations. MSK144 is engineered for Meteor Scatter on VHF bands. FST4 and FST4W target LF and MF bands, achieving fundamental sensitivities near theoretical limits for information throughput; FST4 is for two-way QSOs, and FST4W for quasi-beacon WSPR-style transmissions, without requiring the strict time synchronization of protocols like _EbNaut_. WSPR mode enables propagation path probing via low-power transmissions, incorporating programmable band-hopping. The **WSJT-X 2.7** General Availability release introduces the QMAP program, Q65 Pileup, SuperFox mode, a Hamlib update option, and a Message System. SuperFox mode transmits simultaneously to up to 9 Hounds with a constant envelope waveform, providing approximately +10 dB system gain compared to older Fox-and-Hound operations. _WSJT-X 2.7_ for _Windows_ platforms includes _MAP65 3.0_, a wideband polarization-matching tool for EME. The **WSJT-X 3.0.0-rc1** candidate release represents a major revision with new features, some ported from _WSJT-X Improved_. This software is available for _Windows 7_ and later (32-bit/64-bit), various Linux distributions (Debian, Ubuntu, Fedora, RedHat, Raspberry Pi OS), and macOS (10.13 through 15). DXZone Focus: Weak Signal | Digital Modes | WSJT-X | Windows

A Linux based FFT spectrum analyzer designed for time-frequency browsing and scientific data visualization. Oscilloscope waveform, statistical histogram, accumulated spectral trace,Weak Signal reception, continuos data logging, FFT Analyzer and specialized measurement windows.

WSJT-X, a creation of K1JT, offers specialized digital protocols meticulously optimized for challenging propagation paths such as EME (moonbounce), meteor scatter, and ionospheric scatter. This software excels at VHF/UHF frequencies, and also provides robust performance for LF, MF, and HF DXing, enabling contacts far below the audible threshold. The program decodes signals from ionized meteor trails and steady signals more than 10 dB below the audible threshold, a testament to its advanced digital signal processing. It integrates nearly all popular features from its predecessors, WSJT and WSPR, while adding comprehensive rig control and numerous other enhancements for the serious weak signal operator. Available for Windows, Linux, and Mac OS X, WSJT-X is an open-source project, allowing hams worldwide to download the latest versions and engage in cutting-edge weak signal communication.

TCUBE is a combination of a Spectrum Analyzer and a Two Tone Generator, with optional quadrature outputs. It can be used for measuring the intermodulation behavior of an audio circuit, and as a general purpose tool

A freeware program to dig out weak signals buried in noise, functionally similar to the excellent FFTDSP of AF9Y, but with the added bonus of real time audio filtering of the incoming signals. Just point and click with the mouse, and the selected signal will stand out from the QRM and noise.

Program designed to do spectral analysis and real-time audio filtering on reception of audio signals for EME, VLF, SETI applications. Offer support for MTHELL, QRSS, DFCW, NDB, WSJT by I2PHD

Argo is a freeware windows viewer for MTHELL, Slow CW, like QRSS and DFCW. Can be used for EME operations by I2PHD and IK2CZL

JTDX is an open-source software application for amateur radio weak-signal digital communication. It supports digital modes including FT8 and JT9. The software operates on _Windows_, _Linux_, and _macOS_ platforms. JTDX is designed for improved decoding of weak signals, a function also performed by WSJT-X and MSHV. The software facilitates weak signal decoding and transmission. It integrates with logging systems for QSO management and can automate tasks such as call management and remote RTX control. JTDX is utilized in contexts such as DXing and contests. DXZone Focus: FT8 | JT9 | Weak Signal | Multi-platform

RSCW is a Linux/Unix program for decoding morse signals using the computer's sound card. It has been written/optimized for digging weak signals out of the noise.

Easy circuit that provide good gain to weak audio signals

This relatively unknown antenna does an amazing job pulling weak low band signals out of man-made noise backgrounds

The ICOM IC-7300 is a cutting-edge HF transceiver that has garnered significant attention since its release. This review, published by ARRL in QST, provides an in-depth analysis of its features, performance, and usability. The IC-7300 is known for its direct sampling technology, which enhances its sensitivity and selectivity, making it a favorite among amateur radio operators. The review covers various aspects, including the user interface, audio quality, and overall operational capabilities, providing valuable insights for both new and experienced hams. In addition to its technical specifications, the review discusses the IC-7300's performance in real-world scenarios, such as DXing and contesting. It highlights the transceiver's ability to handle weak signals and its versatility across different modes. The review serves as a helpful guide for those considering the IC-7300 for their station, offering a balanced perspective on its strengths and potential drawbacks. Overall, this review is an essential resource for anyone interested in the ICOM IC-7300 and its place in the amateur radio landscape.

WSJT-X and MAP65, open-source amateur radio programs, facilitate weak-signal digital communication. WSJT-X covers VHF/UHF to HF, decoding subthreshold signals. MAP65 optimizes for VHF/UHF EME with JT65. Free and GNU GPL licensed, WSJT-X is on Windows, Linux, and OS X, while MAP65 is Windows-only, supporting SDR hardware.

Moon bounce EME, meteor scatter and weak signal operations, introduction by ARRL.

LNA Technology High Performance Low Noise Preamplifiers for Amateur Radio, VHF-UHF weak signal, DX, EME, and commercial applications.

A new weak signal DX mode for Radio Amateurs, employing M-ary FSK, phase continous tones and convolutional coded FEC.

JT65 is a digital protocol intended for Amateur Radio communication with extremely weak signals. It was designed to optimize Earth-Moon-Earth (EME) contacts on the VHF bands, and conforms efficiently to the established standards and procedures for such QSOs.

MSHV is a free windows and linux multimode software that support weak signal digital modes like MSK144 MSKMS JTMS FSK441 FSK315 ISCAT JT6M FT8 FT4 JT65 PI4 amateur radio modes. MSHV features several interesting features including the Multi Answering Auto Seq Protocol, allowing multiple signal transmissions to be used during dx peditions.

The 2.1 kHz wide European LF allocation between 135.7 and 137.8 kHz is detailed in this observed band plan, offering guidance for activity within this narrow segment. It specifically addresses the challenge of locating weak signals, such as those from Slow-CW stations, which can have bandwidths of only a few Hertz. The resource emphasizes the utility of precise frequency knowledge when operating with narrow DSP filters, like a 30 Hz filter for CW, to differentiate multiple stations within a very small band segment. The plan, though not officially recognized, provides practical orientation for operators, particularly those new to the _LF band_. It references a similar plan published by the _RSGB_ in the January 2000 issue of _RADCOM_, suggesting a community-driven approach to band organization. The content highlights the importance of spectral awareness, noting that multiple stations can occupy minimal bandwidth, a concept illustrated by spectrographic analysis.

A complete guide to operating the weak signal modes on VHF/UHF/Microwaves. VHF Contesting honor role for the western states, rover, eme basics and vhf contesting.

Operating on the 2200m band (135.7-137.8 kHz) often presents challenges for amateur radio transceivers, which typically exhibit poor receiver performance at these very low frequencies. This project addresses the issue by providing a design for a dedicated 137 kHz antenna preamplifier, specifically tailored to improve signal reception for radios such as the _Yaesu FT-817_. The preamplifier circuit utilizes a low-noise FET input stage, crucial for minimizing self-generated noise and maximizing the signal-to-noise ratio from weak LF signals. The design includes a detailed schematic, component values, and construction notes, enabling homebrewers to build a functional unit. The goal is to achieve significant gain, making the faint signals on 2200m more discernible and improving overall band usability. Key design considerations include impedance matching to typical antenna systems and ensuring stable operation across the narrow LF segment. The circuit aims for a **low noise figure** and sufficient amplification to overcome the inherent limitations of general-purpose HF transceivers when operating below **200 kHz**.

The webpage provides guidance on working 6 Meter DX, focusing on effective operating habits, preparation, and knowledge of the band. It emphasizes the importance of monitoring, clear frequencies, and using CW for weak signals. It also mentions the significance of knowing countries and individual stations on the air to increase chances of working DX. The page recommends utilizing resources like newsletters and websites to stay updated on 6-meter activity and offers suggestions for improving operating skills.

Jason is a weaksignal communication program, especially tailored for LF work.

Amateur Radio operation and weak signal detection pages by AF9Y

Using the Raspberry Pi to operate Weak Signal Propagation Reporter

This page presents a curated list of individuals who have made significant contributions across various fields while also being active amateur radio operators. For instance, Dr. Joseph H. Taylor, co-winner of the 1993 Nobel Prize in Physics for the discovery of binary pulsars, is recognized for developing the _WSPR_ and _WSJT_ weak signal mode software. Similarly, Wilson Greatbatch, inventor of the cardiac pacemaker with over **150 patents**, is featured. The resource details the diverse backgrounds of these hams, from Professor Donald H. Menzel, an astrophysicist at Harvard, to Hiram Percy Maxim, often called "The Father of Amateur Radio," who also pioneered in the automobile and aviation industries. King Hussein of Jordan, JY1, is noted for his active participation on 20 meters, engaging with fellow amateurs like Pat Kilroy, WD8LAQ. Other entries include Arthur M. Young, designer of Bell Helicopter's first model, and Marlon Brando, KE6PZH/FO5GJ, known for operating from his private island in French Polynesia. Peggy Sue Gerron-Rackham, K5PSG, gained her license after a special event station, demonstrating the hobby's broad appeal.

Our group is the North East Weak Signal Group. We are an ARRL affiliated regional club dedicated to the interests of "weak signal" work on the bands 50 MHz -

Accurate calibration of your receiver and sound card is necessary for good results with the weak signal modes in use at LF. Modern receivers with master oscillators that are synthesized to provide all conversion frequencies greatly simplify the process. This article describes a method of making the necessary measurements and adjustments to an ICOM R75 receiver and a sound card, using the ARGO software

CMSK is a narrow-band weak signal digital mode for LF and MF ham radio bands defined by ZL2AFP. CMSK63 is the windows client program.

VHF an above weak siganl site

A very exaustive and complete article on JT65A and JT65-HF operating mode, including software download links, installation notes, how to make JT65A QSO and videos to correctly work with weak signals by NW7US

Introduction to WSPR beacons. Article describe WSPR2 and WSPR15 beaconing mode and include a frequency reference table for both WSPR modes

The complete Bozo's guide to JT65A by K3UK, learn how to install and operate WSJT software and start making QSO in weak signals operating modes

JT44: New Digital Mode for Weak Signals

137.7 kHz QRSS beacon exciter is described, utilizing a single chip for operation on the 2200m amateur band. The design focuses on simplicity and efficiency for weak signal applications, providing a compact solution for generating QRSS signals. This project targets the DX portion of the band, enabling long-distance communication with minimal power output. The resource details the construction and functionality of the **QRSS beacon**, emphasizing its **low-power operation** and suitability for experimental amateur radio. It provides insights into the circuit's architecture and potential for integration into existing station setups. The design aims to offer a practical and accessible entry point for amateurs interested in weak signal modes on the LF/MF bands.

GUI for the KK7KA Wolf software, that was originally written as command line interface only. Wolf is a weak signal software

Elecraft KX2 tips and tweaks about how to improve your receive audio on the Elecraft transceiver

The MMMonVHF database, curated by DL8EBW, currently lists 63,455 entries for VHF operators, providing a searchable resource for locating stations active on 144 MHz and higher bands. Operators can register their callsigns to be included, with specific criteria such as participation in _MS_ (Meteor Scatter), _WSJT_ modes, or _EME_ (Earth-Moon-Earth) operations required for inclusion in the `call3.txt` file. This resource facilitates VHF DX expeditions and contest planning by allowing users to identify potential contacts within a geographical area. The database supports various VHF/UHF operating modes, including those focused on weak signal propagation. Statistical data regarding the database entries is also presented, offering insights into the distribution of registered VHF activity.

Weak Signal Propagation Reporter Network Map and Database of WSPR data

Receiver dynamic range is the ability of a receiver to receive a weak signal without loss of readability while a strong signal is present.

It has been 40 years since the VHF-UHF Quagi antenna--a combination of the desirable features of a Yagi and a cubical quad--was developed and the design was first published in the newsletter of the Southern California VHF Club, a forerunner of today's Western States Weak Signal Society.

Linrad and SDR-IQ Software Defined Receiver on Shortwave

JT9 is a amateur radio weak-signal digital mode can give little pistol stations big gun results, ARRL article by W4GAL

Morse Code Decoder for Android based on the algorithms implemented in CW Skimmer. Morse Expert decodes Morse Code audio to text. It is optimized for decoding weak, fading signals in the presence of interference, especially on the Amateur Radio bands. The input audio might come either from the built-in microphone or from another device, such as a radio receiver.

An excellent guide to operating FT8 mode available in English, German and Czech that cover several aspects of the FT8 operations. Includes and exaustive guide to how configure FT8 software, how to conducto a QSO and how to operate DXPeditions in FT8 F/H mode. Covers aspects of FT4 contesting operations and interfacing with logging programs