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SWR and Transmitters Friends or Foes!, making sense of it!

Lancaster Radio Transmitting Society Lancaster County, Pennsylvania

How to improve your transmitting antennas for very low solar activity periods, vertically polarized 160 meter antennas, horizontally polarized 80 to 10 meter antennas, single or stacked yagis, multi-tower stations

Demonstrates the fundamental principles for connecting a personal computer to a ham radio transceiver, specifically for utilizing sound card-based digital mode software like those in the MM Hamsoft suite. It details the basic hardware setup, emphasizing the use of shielded leads and proper audio routing from the radio's output to the sound card's input, and from the sound card's output to the radio's microphone or data input. The resource highlights the critical need for transmit attenuation, suggesting a 100:1 voltage divider to prevent overdriving the transmitter's audio stage, and mentions the optional addition of ferrite beads and decoupling capacitors for RFI mitigation. The guide also points to external resources for more detailed pin-outs and interface schematics, such as a specific QSL.net page, and recommends consulting the help files within MM Hamsoft programs for interfacing specifics. It underscores that while the process is straightforward, understanding the audio level management and proper cabling is key to successful operation. The author, VE5KC, provides practical advice drawn from common issues encountered by operators setting up digital mode stations.

A cavity filter, often a critical component in _duplexer_ designs, functions as a sharply tuned resonant circuit, allowing only specific frequencies to pass while attenuating others. These filters are essential for maintaining signal integrity in environments where multiple transmitters and receivers operate simultaneously on closely spaced frequencies, such as in repeater stations. The article details how these filters, sometimes referred to as _notch filters_, achieve high Q factors, which are crucial for their performance. Understanding the principles of cavity filters is fundamental for any amateur radio operator involved in repeater operation or designing custom RF front-ends. The discussion covers the basic circuitry and operational characteristics that enable these devices to provide significant isolation, often achieving **-80 dB** or more between transmit and receive paths. This level of isolation is vital for preventing receiver desensitization and intermodulation distortion. Properly tuned cavity filters ensure that a repeater can transmit and receive simultaneously on different frequencies without self-interference, a common challenge in VHF/UHF operations.

The Malaysian Amateur Radio Transmitters' Society (MARTS) serves as the national representative body for amateur radio operators across Malaysia, having been established in 1952. This organization plays a crucial role in advocating for the interests of Malaysian hams, fostering community engagement, and supporting the growth of the amateur radio service within the country. MARTS actively participates in national and international amateur radio affairs, often collaborating with organizations like the _International Amateur Radio Union_ (IARU) to ensure the continued development and recognition of amateur radio. The society's activities encompass a range of services for its members, including the dissemination of information regarding licensing, operating procedures, and technical advancements. MARTS also facilitates various on-air events and provides resources to help members improve their operating skills and expand their knowledge base. The organization's long-standing presence since 1952 underscores its commitment to the amateur radio community in Malaysia. MARTS supports local clubs and individual operators, promoting best practices in radio communication and emergency preparedness.

A page dedicated to top band transmitting equipment and operations by VK3YE

The 2200-meter band (135.7-137.8 kHz) presents unique challenges for amateur radio operators due to its narrow 2.1 kHz bandwidth, low signal levels, and high noise. W1TAG explores various transmission modes suited for this demanding environment, highlighting that traditional voice modes like SSB and AM are impractical. Plain old CW serves as the baseline, demonstrating effectiveness across different modes, though signal-to-noise ratio (SNR) significantly limits practical speeds. The article notes that reducing CW speed below 5 WPM can improve copy, especially with computer-aided spectrum analysis software capable of decoding signals too weak for human ear reception. QRSS, or "CW sent slowly enough that speeds are best expressed in seconds per dot," is a key mode for LF work, with examples ranging from 3 seconds/dot to extreme 240 seconds/dot transmissions. _Argo_ by I2PHD is mentioned as a simple program for QRSS, enabling reception of signals like BRO, a Part 15 beacon, at a distance of **1100 miles**. Other modes discussed include Dual Frequency CW (DFCW), which uses frequency shifts to distinguish dots and dashes, and Binary Phase Shift Keying (BPSK), a phase modulation technique employing 0 to 180-degree phase flips. WOLF (Weak-signal Operation on Low Frequency), a specialized BPSK form by KK7KA, encodes 15-character messages into 960-bit packages, taking 96 seconds to transmit, and has demonstrated successful reception over **672 seconds** for a message from a 1-watt beacon. Further modes include PSK, FSK variations like JASON and MSK, and graphical modes such as Hellschreiber and Chirped Hell. The article concludes with a practical chart comparing the time required to send a simple message like "WD2XES FN42CH " across these diverse LF modes, offering valuable insights for operators planning contacts on the low bands.

A CW beacon keyer for 222 MHz by VA3NFA

Fixing the problem with VHF-LED coming on while transmitting UHF

Amateur radio repeaters extend communication range for mobile and remote stations by retransmitting signals on a different frequency, often for emergency communications. The resource details various repeater bands, noting that 2 meters and 70 cm are primary for activity, with 10-meter repeaters offering potential national and overseas coverage. It specifies **18 channels** on 6 meters and **31 channels** on 2 meters, along with a new 70 cm offset of _7 MHz_ adopted in 2015. The content explains how repeaters can be linked via dedicated transmitters/receivers, landlines, or Internet VoIP systems like _IRLP_ and Echolink, enabling global connections. It also describes simplex gateways for multi-band operation and the use of CTCSS subaudible tones for access control and interference mitigation. The document highlights specialized repeaters for modes beyond voice, such as SSTV and ATV, particularly on 70cm and higher bands. Operational guidelines for efficient and courteous repeater use are referenced, along with links to Australian repeater listings and band plans.

Issued by the Irish Radio Transmitters Society

WD2XSH Experimental Station (505 - 510 KHz) WD2XKO Transmitting Station Stanfield,NC operating between 135.7 to 137.8 KHz.

The Triangle ATV Association is an organization of hams in the Raleigh-Durham-Chapel Hill NC area who communicate by means of our own personal TV transmitters and receivers.

A blog site dedicated to SSTV Slow Scan Television images transmitted from the International Space Station

A guide to properly use FT8 ALC and power when transmitting in FT8 Mode. Incorrect usage of power and audio from your computer may cause unreadable signals and transmit harmonics that can didturb other signals.

The Doppler Effect allows the distance between a satellite transmitting from space and a radio receiver on the ground to be measured by observing how the frequency received from the satellite transmitter changes as the satellite approaches, passes overhead, and moves away.

High Frequency Expermental Beacon "WV". The Beacon operates on the frequency of 13.55567mhz. This Beacon is very low power. It operates under Part 15 of the FCC Rules and Regulations. It transmits with only 1.5 milliwatts of power

Founded in 1959

The details of the spark gap transmitter and its history: how it was invented, developed and used.

An improved version of the audio interface commonly used to connect a computer soundcard to a transceiver\'s receive and transmit audio circuits

ELENOS is the leader company for fm transmitters, amplifiers, radio broadcast equipment and custom systems.

Before the advent of digital transmission modes, several analog schemes were developed to transmit images or image-like information on the Amateur Radio bands.

RTTY transmissions with audio boards, can be transmitted either in FSK or AFSK mode. Learn differences between this two different modes by IK3QAR

This circuit stores a morse code message as bits in an EPROM chip, the message controls a relay that keys a CW morse code transmitter. An Arduino processor can also be used in place of this circuit, that eliminates the need to build the circuit and program an EPROM.

The equipment shown on this page comprises a basic G3WDG transmit and receive system with the addition of a 1W Qualcomm amplifier.

Build a SPDT coaxial relay that can be used as a main Transmit/Receive relay or an A-B switch to select between two different 6m antennas

QRSS operations on 30M with an home made dipole

Amateur Television (ATV) operations involve transmitting and receiving live or recorded video and audio signals over amateur radio frequencies. Unlike narrow-band modes, ATV utilizes a wider bandwidth to convey video information, often requiring specialized transceivers, antennas, and signal processing equipment. This mode allows hams to share visual content, demonstrate projects, or conduct video conferences, typically on VHF, UHF, and microwave bands due to the bandwidth requirements. The SwissATV resource focuses on the technical aspects and community engagement surrounding ATV within Switzerland. It covers topics relevant to setting up ATV stations, understanding signal propagation at higher frequencies, and participating in local ATV activities. The site serves as a central point for Swiss ATV operators to exchange knowledge and coordinate transmissions, fostering the growth of this specialized amateur radio mode.

A homebrew radio transmitter project, based and inspired by the original 30 Watts input on 80 50 and 15 meters band transmitter by W11CP

What is VSWR and why you should care, formal definition of VSWR and SeaSonde Measurements, formulas

Sixty-meter repeaters typically use a 1 MHz frequency separation between input and output, while 2-meter repeaters commonly employ a **600 kHz** split and 70-centimeter repeaters use a **5 MHz** offset. This article details the fundamental technical principles of amateur voice repeaters, explaining how they extend VHF/UHF communication range by receiving on one frequency and simultaneously retransmitting on another. It covers essential components such as receivers, transmitters, filters, and antennas, often situated on elevated locations for optimal coverage. The resource delves into the critical challenge of _desensing_—where the repeater's strong transmit signal overpowers its own receiver—and the engineering solutions employed, including antenna separation and the use of high-Q cavity filters. It also explores various control and timing systems, from basic squelch activation to more sophisticated microcontroller-based boards that manage functions like voice identification, time-out timers, and fault protection. Different access methods are discussed, including open access, toneburst, CTCSS subtone, and DTMF, each offering distinct advantages for managing repeater usage and mitigating interference. Furthermore, the article examines repeater linking, both conventional RF methods and modern internet-based solutions, highlighting how linking expands coverage and promotes activity across multiple repeaters or bands. It introduces less common repeater types such as 'parrot' repeaters, which use a single frequency and digital voice recording, and linear translators, capable of relaying multiple signals and modes simultaneously across different bands, often found in amateur satellites.

From 1921 to 1924, radio amateurs experimented with transmitting across the Atlantic. Everyday Engineering magazine organized the first sending test with English amateurs prepared to listen for signals from the US

A transmitter project for the 136 kHz band by IK2PII

When one starts in amateur television, one begins with a small simple transmitter and a small camera. But very quickly, one needs to transmit audio signals with the pictures, then comes a second camera

Microprocessor based interface designed receives a signal from a Morse key, processes it, and re-transmits it to the radio. A microprocessor in the circuit is pre-programmed with a proprietary algorithm which makes a number of measurements and adjustments to the less percise human generated code.

This article describes the construction of a high performance transmitter and receiver for SSB (voice) communication covering the 14MHz (20 meters) high frequency amateur radio band with output range 15 to 20 watts and a top audio sound quality both on transmit and receive.

It is possible to add a very small Bluetooth transmitter to the 3.5mm headphone jack and then use a pair of Bluetooth headphones around the shack. In this article Author provides some tips on choosing the proper Bluetooth interface.

Producers of custom name tags, luggage tags, club badges, Employee Name Tags, Special Event Badges, but also Comtech Amateur Radio Television Transmitters and Receivers D480 filters, Video cameras and accessories.

Drake TR-7 A.M. Transmit Filter Modification

Receivers and transmitters by Collins , Drake , Hallicrafters , Hammarlund , National Receivers

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.

How to limit unwanted harmonics from your raspberry Pi radio transmitter by introducing filters.

An home made antenna switch with a Dummy Load selector. If you forget the radio is connected to the open or grounded side of the switch and you try to transmit, it is very easy to damage the finals of your transceiver.

The N0QBH QRSS project page, a couple of projects using available kits for improved frequency and timing stability. A configurable DDS VFO 100mW transmitter with LCD display and a modified Hans Sommers 40m 100mW transmitter

Amateur Radio Transmitting Society located in Louisville, KY

Since 1946, VK6 Weekly News has delivered weekly broadcasts to amateur radio operators across Australia, particularly in the VK6 region. The broadcasts include news updates, acknowledgments of contributors, and calls for operators to engage by transmitting news or submitting stories. This initiative strengthens community ties among amateur radio enthusiasts and encourages collaboration in maintaining the network of repeaters. The broadcasts reach various states, including Western Australia, Queensland, and New South Wales, ensuring that information is disseminated widely. VK6 Weekly News emphasizes the importance of operator contributions, thanking them for their efforts in sustaining the amateur radio community. Accessible through multiple platforms, it supports ongoing amateur radio activities and development in the region. Operators are invited to participate actively, enhancing the richness of the news content and fostering a collaborative spirit within the amateur radio community.

A microprocessor based interface designed to go between a standard Morse code key and a radio transmitter. The circuit receives a signal from the key, processes it, and re-transmits it to the radio.

PSK Reporter provides a real-time visualization of amateur radio digital mode reception reports, aggregating data from a global network of monitoring stations. This platform is particularly useful for operators utilizing modes such as FT8, FT4, and PSK, allowing them to observe signal propagation paths and assess their station's reach. The interactive maps display reception reports, enabling hams to analyze band conditions and optimize antenna performance for various frequencies and times of day, aiding in understanding ionospheric conditions. Operators can filter reports by callsign, band, mode, and time, gaining insights into specific propagation events or evaluating the effectiveness of their transmit setup. The data collected helps in predicting optimal operating windows for DX contacts across various digital modes. Philip Gladstone is the contact person for comments and discussions regarding the system.

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.