circuit cad

The 4X4 Slimtenna - Development of the Slim Jim antenna for HF

PortalPMR - Spanish Transceiver forum with classifieds

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.

Adding 160 meters to the Heathkit SB-220 - There will be radical changes to this Heathlit SB-220. There will be the addition of 160 meters along with many other circuit and design changes.

Yaesu FT-920 Inrad CW Filter Mod - This modification allows the use of two filters. Either one or two filters in cascade may be selected

Omnidirectionnal antenna for the 23 cm band - Building an omnidirectionnal antenna for the 23 cm band

Experimental 2 Mbit modem - Description of a 2 Mbit Modem project

Transistor PA Biasing - Here is a simple circuit that can deliver the peak base current needed for linear ssb operation

Transistor PA Biasing - Here is a simple circuit that can deliver the peak base current needed for linear ssb operation

Integrated Circuit Audio Amplifiers - Circuit designs for IC audio amplifiers by N1HFX

Design Guidelines for JFET Audio Preamplifier Circuits - Design Guidelines for JFET Audio Preamplifier Circuits By Mike Martell N1HFX

Adjustable Regulated Battery Charger - This battery charger circuit is regulated and adjustable to make this circuit able to charge the mosto NiCAD battery.

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

The express-pizza antenna - Build a directional antenna for the 1.2 GHz band, in 15 minutes

RF Dummy Load - The use of dummy load is mandatory for off-air adjustment of the transmitters. Build one.

DC RF Sensing PA Switching - Circuit for dc/rf sensing pa switching from g8mny

Noise Bridge Tuner Tuner - Noise bridge circuit to tune your tuner

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

QLF Filter - 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.

A low cost morse Trainer / Keyer - By Prof. T. K. Mani - VU2ITI

FT290 CW KOX Circuit - This is not actually break-in but just KOX circuit. It can only be used on the CW mode otherwise it keys up the Tx

Non-relay instant RF Switching - Coax lines to do the RF switching. The advantages are instant switching, no power wasting DC control circuits.

An Accurate Power Meter For QRP Ops - A circuit using two junkbox transistors and a garden variety op-amp that will let you accurately measure your rig\'s flea power down to milliwatts.

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.

Oscilloscope Tester - Circuit to assist in the setting-up and calibration of oscilloscopes