circuit specialists

Z-Match Antenna Tuner project - This Z-Match is a link coupled all-band tuner. Two all band tank circuits cover 3-14mhz and 14-30mhz. The tank output links are selected with a very heavy duty SPDT rotary switch.

Variacs - Variable Autotransformer - Use these Variac auto transformers for specific application requirements that include, but are not limited to, home coffee roasting, tube amps, and more.

SB-220 Repairs and Modifications - Heathkit SB 220 mods, replacing the Zener ZD1, replacing the plate-voltage voltage divider, adding a keying circuit for solid state transceivers

Osmond PCB - Printed circuit board design for Macintosh

60 W Linear Amplifier Circuit  ^updated - The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840.

A NiCAD Battery Charger - A NiCAD Battery Charger with Current and Voltage Limiting

About Cavity Filters - Cavity filters are tipically circuitry behind a duplexer that allow only certain frequencies to pass

Cheap Crystal Filter - An economical way of building an SSB filter. The circuit is for a filter with a 6 DB band width of roughly 2.2 KHz.

RF Sampler - This circuit will let you look at the signal and frequency output of your transceiver.

PC Headset Adapter for Ham Radio - A PC headset to Rig adapter. Include a circuit diagram and a full part list for the project

Morse Keyer Circuit - This is not a sophisticated automatic keyer but it is lot QRP to build and to have fun operatin

600v Power Supply - A 600 volts power supply for QRO

Circuit Improvements for the TS-440S - Some improvements for the Kenwood TS-440S, including distortion level in SSB in transmitted signals, Lack of crispness in the RX audio and Limited transmit frequency coverage.

Icom CI-V Interface - Build this CI-V interface and the additional circuitry to provide PTT from RTS.

Sound Card Interface with Tone Keyer - An improved version of the audio interface commonly used to connect a computer soundcard to a transceiver\'s receive and transmit audio circuits

CI-V Interface Controller  ^new - Acircuit that will please many, a cheap alternative to expensive TN,firstly then we look at the CI-V type port to connect to the interface.

Grip Dip Oscillator - Originally eveloped by I1FLC, uses seven plug in coils covering 3.0 to 30Mhz in a Colpitts oscillator circuit.

Build a Test Meter - This article include a circuit that allows a cheap 0-1mA meter to be used as a micro-ammeter or a milli-voltmeter

Make your own multimeter - Homebrew a multimeter with this article

The OscilloScope Tutorial  ^new - How Oscilloscope works and how oscilloscopes are done, with main components like Vertical Amplifiers and Horizontal Scanning or Sweep Circuits

RF Probe circuit - This RF probe circuit allows RF to be measured in the presence of DC

RF Probe for HF - A RF Probe circuit for the RADIO frequency experimenter to check the presence of a RF signal and also to measure its strength

RF Probs and Watt meter - This RF probe can be used at High Frequency (HF) or Ultra High Frequency (UHF) on both 50 and 75 ohm coaxial cables.

A DIY Square Wave Signal Generator - This circuit is very simple and has a fantastic range of potential uses.

ZL2PD HF RF Signal Generator - This circuit came out of some work done for two antenna analysers