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Online VSWR Voltage Standing Wave Ratio Calculator

SPX Communication Technologies, operating under the TCI International brand, presents a range of radio frequency (RF) solutions primarily for government, defense, and commercial sectors. The offerings include advanced systems for spectrum monitoring, communications intelligence (COMINT), and high-frequency (HF) and medium-frequency (MF) broadcasting and communication antenna systems. Specific product lines encompass _Blackbird_ COMINT systems, _Scout_ spectrum monitoring receivers, and various antenna arrays designed for robust performance in challenging RF environments. The resource details the capabilities of these systems, such as wideband signal detection, direction finding (DF), and signal analysis, crucial for intelligence gathering and regulatory compliance. It also highlights the engineering behind their antenna designs, which are optimized for specific frequency ranges and operational requirements, including high-power broadcast applications and secure military communications. The information presented emphasizes the integration of hardware and software for comprehensive RF situational awareness. The company's focus on empowering partners to "Command the Spectrum" underscores its commitment to delivering critical tools for signal interception, analysis, and management across diverse operational landscapes.

The Hexbeam is a great little antenna! It should be high on your list of options if you want a design that can be multi-banded, exhibits useful gain and directivity, is very lightweight, has a small turning radius, and which lends itself readily to Do It Yourself construction.

Tables comparing attenuation of common coax cables on amateur radio bands

D-Star article by wikipedia.

Simply work as many countries and CQ Zones as you can in each calendar year, regardless of the band or mode

The Southwest Metro Amateur Radio Transmitting Society, Inc. is a non-profit club dedicated to promoting the Amateur Radio hobby.

This page is a short description of the four phased verticals system for 160m 80m and 40m

Amateur Radio on the International Space Station european web site

Information on ham radio or amateur radio (radio amatur)

Six meters is a great band for home built Yagis. The elements are reasonably small, but not so small that building tolerances are critical. With careful construction and detailed instructions, it is certainly feasible to build no-tune Yagis up to 432 MHz.

A web site about amateur radio satellite

A workaround to common RF interference on Samsung TV LED causing several issues like changing channel, swithcing to demo mode, or changing volume.

Plastic tubing and custom plastic tubing from a manufacturer that specializes in the custom manufacturing of close tolerance plastic tubing products.

An interesting presetnation full of usefull tricks to correctly design and build 23 cm Yagi using simple tools. The basic design of the antenna presented in this document is taken from the original DL6WU Yagi Design published in 1982

IARU NCDXF Beacon in Sri Lanka 4S7B working on 14.100, 18.110, 21.150, 24.930, and 28.200

Maldives 1998 by the Berlin-DX-Group

Balloon Experiments with Amateur Radio

Centerloaded mobile antenna Handy for stationary, mobile and portable operations

Mobile RFI, often manifesting as persistent noise in the receiver even with the antenna disconnected, frequently originates from the vehicle's power supply system. This guide details systematic troubleshooting steps, beginning with isolating the radio from the car's 12-volt supply to confirm the power system as the noise source. It emphasizes the critical importance of drawing power directly from the battery using **heavy gauge wire**, bypassing the fuse block to leverage the battery's natural capacitance for RFI suppression and ensuring a solid RF ground. Proper routing of power lines through the firewall is also covered, advocating for dedicated grommeted holes to prevent inductive coupling from other wiring harnesses. The article stresses the necessity of fusing both positive and negative leads from the battery, a crucial safety measure to prevent damage to the rig and mitigate high-current risks should the battery's engine block ground become compromised during service. Addressing **alternator whine**, a common high-pitched noise that varies with engine speed, the resource suggests checking battery connections and the alternator-to-battery harness for looseness or corrosion. It also mentions the utility of adding an external RF noise suppression capacitor in parallel with the alternator's internal capacitor for enhanced filtering, and the effectiveness of commercially available in-line power supply filters.

Test equipment, counters and meters

W6CQZ JT65-HF project on sourceforge, the Amateur Radio software for reception/transmission of JT65A protocol with an emphasis upon its usage in the High Frequency Amateur Bands. Project is currently paused.

A 500 kHz to 5.5GHz 2-port vector network analyzer designed for use with any Linux, Windows or MacOS computer. High performance: up to 80 dB dynamic range in the MHz range; up to 40 dB in the GHz range

A sound file collection of QRP contacts by AE5X

CW, padlles key collection

Aamateur radio club affiliated with the Amateur Radio Relay League (ARRL) from Fitchburg Massachusetts. MARA owns and operates the W1GZ repeater 145.45- with a tone of 74.4.

80 watt multi-mode amplifier using one of the newer S-AV36 Toshiba modules. Less than 50 milliwatts will drive it to full output in any mode.

For over 50 years, Communications Specialists Inc. has been a cornerstone in specialized radio frequency solutions, initially gaining prominence with their **CTCSS** and **DTMF** tone signaling products widely used in amateur radio repeaters and commercial two-way radio systems. My own experience with their tone boards in various repeater builds confirms their reliability and ease of integration, a testament to their engineering. The company's legacy in tone encoding and decoding is well-established, providing robust solutions for access control and selective calling. Beyond tone signaling, Com-Spec has diversified into niche markets, including wildlife telemetry, pet tracking collars, and specialized tracking systems for model aircraft and rocketry. Their product line features compact transmitters and receivers designed for specific tracking applications, demonstrating a commitment to precision and durability in challenging environments. While some legacy products are no longer available, Com-Spec continues to innovate, as evidenced by the new R-30M receiver, which ships within five days. This focus on specialized RF applications, from tracking Alzheimer's patients to law enforcement, highlights their unique position in the radio communications industry.

About greyline propagation in HF bands

Pictures of home made antenna launchers

OCCARO is a membership organization formed for the benefit of all Amateur Radio clubs in Orange County, CA and neighboring counties.

Using absurdly low-speed CW for "communications"

Raytown Amateur Radio Club - Kansas City/Rsytown, Missouri

Welcome to The Stillwater Amateur Radio Association

Pictures of a homemade monoband linear amplifier for 160m band powered by 3 x QB5/1750

Spanish swl dx club

We stock a range of two way PMR446 radios. PMR 446 is a license free frequency, which means that you can communicate for up to 3km (terrain allowing) without any call charges or license requirements. They can be used in most European countries and are ideal for holiday trips.

The first and only BCB DX club in the Czech Republic and Slovak Republic, established in 1990.

DXpedition by Rene/DL2JRM, Bodo/DL3OCH, Dan/DL5SE, Daniel/DL5YWM & Anett/DO6XX

Heavy duty digital multimeters

QRSS pictures and examples from IW0HK ex IW1CXZ

The Ham Cram method is designed to prepare you for the FCC tests in the shortest time possible giving you the highest level of confidence. It's totally free.

Organizacion Argentina especializada en Emergencias y Servicios a la Comunidad.

How to compile and configure WSPR on a Raspberry Pi

A web site for those interested in ham radio Software Defined Radio (SDR). SDR Zone provide forums, reviews and user blogs relating to any type of SDR

A Collection of EME Reflector Antennas and YAGI Arrays.

STC, AWA, Valve Radio, Airzone, Kriesler, Mullard, Western Electric, dating Australian radios

Crystal receivers, construction projects and plans, old-time crystal sets, hints, crystal receiver store.

High speed telegraphy without key clicks by SM5BSZ

LPI personnel have combined experience over many years in servicing customers throughout the world. Our experience covers projects in some of the most lightning prone areas.