Search results

A simple RF probe diagram

Pro and cons of Digital ATV versus Analogue ATV

Make your own battery clip by nj2x

A trapped multi band end-fed-half-wave antenna for 40/30/20/17/15m.

The N1HFX thermal cooling fan controller project details a practical circuit designed to manage cooling fan operation based on temperature, a common requirement for high-power amateur radio equipment. This build utilizes a **LM34** temperature sensor, providing a linear voltage output directly proportional to Fahrenheit degrees, simplifying the control logic. The circuit's core functionality involves a comparator that activates the fan when a preset temperature threshold is exceeded, ensuring efficient cooling and reducing unnecessary fan noise. This controller is particularly useful for amplifiers, power supplies, or transceivers that generate significant heat during operation. The design incorporates a _TIP120 Darlington transistor_ to drive the fan, capable of handling up to 5 amps, making it suitable for a range of fan sizes and current requirements. Field results indicate stable temperature regulation, preventing thermal runaway in enclosed environments. Construction involves readily available components, making it an accessible project for hams looking to optimize their station's thermal management.

Build a 7 Element 4M (70MHz) Beam By Paul M1CCZ

A CW beacon keyer for 222 MHz by VA3NFA

A summary of common calling frequency for each digital mode on that band.

Pictures of the restructuring of the ham shack starting from an existing garage. Changes includes isolation of walls and roof and rebuilding of the radio table.

Switching Regulator Basics By Mike Martell N1HFX

Circuit designs for IC audio amplifiers by N1HFX

DTMF Keypad for radios without one. A project with picture and schematic diagrams to homemade a DTMF keppad

A fully documented restoration project of a Hallicrafters SX99 receiver

The purpose of this article is to provide radio amateurs with enough background information to understand the technical challenges involved in small-station digital EME on the 144 and 432 MHz bands.

A multi band antenna for HF band capable to operate from 10 to 80 meters band depending on wire lenght loaded with a small inductance neat the feed end.

A DIY aluminium push up mast project. The final mast includes 7 aluminium tubes with 6 cable clamps

Tutorial about writing a software SSTV modulator/demodulator using slant correction and several improvements. It requires programming language knowledge and programming skills.

The Shoddytenna is a 160 meters band vertical antenna intended for portable use. This antenna takes just 15 minutes to erect on site, can be carried by hand and is ideal for local groundwave work.

Use your Smartphone as an Oscilloscope to visialize signals from 150 Hz to 15kHz and as a Signal Generator to generate sinusoidal, square and triangular signals up to 15kHz

How to make a Morse Code Oscillator

Constructing a basic multimeter involves integrating a 0-1mA meter movement with various shunts and multipliers, selected via a switch, to create a versatile instrument capable of measuring DC volts, current, and resistance. The design outlines two main units: a primary unit handling six DC current ranges up to 1 amp and eight DC voltage ranges up to 1000 volts, alongside an internal battery for an ohms range up to 200,000 ohms. This approach allows for a practical, hands-on understanding of meter operation. An add-on unit further extends the multimeter's capabilities, incorporating a meter rectifier and switched series resistors to provide four AC voltage ranges up to 100 volts. Additional shunt and series resistors, designated Ra and Rb, are included to expand the instrument's range to 10A and 5kV, demonstrating how modular design can enhance functionality. When this add-on is in use, the main instrument is set to measure 1mA FSD, connecting via specific lugs. Component selection emphasizes precision, with 1% tolerance high stability resistors for series elements and Eureka resistance wire for shunts. The design specifies values calculated for a meter with 60 ohms internal resistance, noting that these would require modification for different meter characteristics. Experimental adjustment of shunt values is recommended to ensure accurate readings against a calibrated reference meter, reinforcing practical calibration techniques.

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.

A 3.2m EME dish project that provides a better performance on 1296 MHz (10+dB sun noise vs. 6dB with my 432 array) and an even better performance on 2304 MHz

Tips and tricks for succesful soldering. An illustrated guide for beguinners and an usefull reminder for expert in soldering.

This DIY vertical multi-band Windom antenna offers a practical and effective solution for amateur radio enthusiasts seeking a versatile and compact antenna for HF communications. Its simplicity of construction, multi-band capability, and favorable performance make it a valuable addition to any radio shack. The article provides detailed instructions on constructing the antenna and balun, along with diagrams and component specifications. Field tests demonstrated successful contacts with stations across Europe and North America on 14, 18, and 28 MHz. The antenna exhibited comparable performance to a W3DZZ dipole and outperformed a Cobweb antenna on 18 MHz. Low noise levels were observed, effectively suppressing background noise.

This project takes after the VGA-to-Scope converter by using composite video rather than VGA signals to create a display on an oscilloscope.

Building the Three-Element Hex Beam. A project and construction phase of an HF hex-Beam antenna using trees to hang the antenna and a Channel Master antenna rotator.

PropNET is an ad-hoc 2-way (and potentially, "more-way") RF-based digital communication network whose activity is reported on the Internet. As participating stations periodically ID and exchange data, they report their activity to an Internet data-collection hub for presentation through this web site.

An universal antenna tuner interface, the Kenwood Remote LDG Tuner Interface by af6sa

Build a digital AC voltmeter to measure the output range from 0 to 150VAC with reasonable accuracy

HM-36 Modification to make it work with an IC-7200 and the IC-7600

A 3CX1500/A7 8877 144mhz W6PO amplifier, that running a little over 4kv on the plate, this Amp will do over 2kw out.

Homemade an external T/R switch for your vintage RTX by KB8OJH

Schematic diagram of a two tone audio oscillator by VK3YE

This antenna is an off-center fed spiral dipole for 40 meters. The spiral dipole is very compact, making it well-suited for limited space (like an apartment patio), while the off-center feed gives the antenna some multiband capability.

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.

An experimento of a 40 meter delta loop antenna both in horizontal and vertical polarization and several elevation angles with interesting notes about the effect of the radial field under the antenna.

A discharge circuit which you could use to cycle the batteries

While transistors have many uses, one of the less known uses by amateurs is the ability for bipolar transistors to turn things on and off

A page with pictures of the Ameritron AL-80B Amplifier, including the inside box where is possible to see the 3-500ZG tube capable to provide 800W in CW.

A homebrew project about a bluetooth interface to connect a transceiver to an audio headset.

Converting a computer\'s VGA output for an oscilloscope

Fox Controller, designed by VE2JX and VE2EMM includes schematic diagram to build the transmitter.

The home page of WSJT-X Improved, an enhanced version of WSJT-X, the popular tool for hams interested in digital modes such as FT8 and JT65. The software provides enhancements and improvements to the original WSJT-X program, making it easier and more efficient for ham operators to communicate digitally. Whether you are a beginner or an experienced operator, this download can help enhance your digital communications capabilities. Free downlaod and full description of improved features.

Mirage BD-35 2M/70CM RF amp high SWR, how to troubleshoot

A new ham radio shack desk made of a solid core oak door.

This is a project aboout compact and portable a QRP antenna tuner for use in the HF ham radio bands from 3-30 MHz, even if it's a compact and efficient project this small antenna tuner will not match any possible load.

A Fox transmitter by VE2EMM with construction details part list and schematic diagram

Thsi article describes a microcontroller driven semi-automatic antenna tuner capable of handling power levels up to 150 watts. The device is a low pass filter tuner manually tuned by setting the optimized L/C combination by hand and then storing the values into the EEPROM of the mictrocontroller to recall them later (seperately for each band from 80 to 10 meters including WARC bands)

Launch of a hybrid rocket from high altitude by untsville Alabama L5 Society