SECARS Project Page

Our members have created a lot of homebrew projects.  Their designs and construction notes are shown below.  These items range from station accessories to rig enhancements, antennas and even QRP transceivers.  These projects can all be built using parts from electronic distributors listed on our Useful Links page.  Check out some of these designs, and get building!

Audio Tone to PTT Keyer

This circuit translates audio tone to a PTT pulse

by N1HFX

tonekey

2M 5/4 Wave Antenna

Build a 2-meter 5/4 wavelength antenna.

by N1HFX

ant54

70 cm Collinear Antenna

Build a 9 dBi 70cm collinear antenna from coax.

by N1HFX

collant

10 Amp, 13.8 Volt Power Supply

Build a 10 amp 13.8 volt power supply.

By N1HFX

powsupply

Inexpensive Tone Decoder

These are plans for an inexpensive PL tone decoder

by N1HFX

decoder

Improved PL Tone Encoder

This circuit has greater stability under loading.

by N1HFX

impdecod

Pass Transistor Voltage Regulator

This project describes how pass transistors improve current capacity for regulated supplies.

by N1HFX

vreg

Condenser Microphone

Instructions on how to homebrew a condenser microphone.

by N1HFX

hbmic

Simple Electronic Keyer

This is a simple electronic Morse Code keyer with no memories.

by N1HFX

cwkeyer

Another Electronic Keyer

This is a single chip Morse code keyer.

by N1HFX

keyer

FM Morse Code Keyer

This circuit connects a simple 555 oscillator to the mic input of your FM radio

by N1HFX

fmkeyer

80 Meter QRP Transceiver

Plans for a complete 80 meter 5 watt transceiver

by N1HFX

rose80

Simple Electronic S-Meter

This is an LED bargraph-based S-meter for receivers.

by N1HFX

smeter

100 KHz Crystal Calibrator

Plans for a 100 KHz crystal calibrator for analog VFOs.

by N1HFX

calibrat

High Performance Voltage Regulator

Plans for a high performance voltage regulator from discrete components.

by N1HFX

discreg

12 Volt Gel Cell Charger

Build a gel-cell battery charger for QRP expeditions.

by N1HFX

gelcell

Audio Speech Processor Circuit

An audio speech processor circuit to give your transmitted signal some punch.

by N1HFX

speech

Thermal Controlled Fan Switch

This circuit turns on a blower fan when your equipment is running hot!

by N1HFX

fancont

40 Meter QRP Transmitter

Build a 5 watt 40 meter CW transmitter.

by N1HFX

transmit

Several Audio Amp Circuits

This article describes several designs of audio amplifiers

by N1HFX

transaud

Integrated Circuit Audio Amps

A paper describing op-amp based audio amplifier circuits.

by N1HFX

icamps

Basic VOX Circuit using 1458

A basic VOX circuit using a 1458 dual op-amp chip.

by N1HFX

basicvox

Homebrew 4:1 Balun

Instructions on how to make your own homebrew balun!

by N1HFX

balun

Simple Rechargeable CMOS Battery

This circuit replaces the CR2032battery in your CMOS circuits with a rechargeable version

by N1HFX

cmosbatt

Variable Bandwidth CW Filter

A simple audio filter for CW signals - with variable bandwidth

by N1HFX

cwfilter

Adjustable Voltage Regulators

A paper illustrating concepts with adjustable voltage regulator ICs.

by N1HFX

regulator

Designing JFET Audio Preamps

Design principles for J-FET based audio preamplifier circuits.

by N1HFX

jfetamp

Op-amp Based Preamplifier Design

Design principles for audio preamps using op-amp components.

by N1HFX

opamps

Switching Regulator Basics

Basic principles for the use of switching regulator circuits

by N1HFX

swregdes

Bipolar Transistor Switches

A paper describing the use of bipolar transistors as electronic switches.

by N1HFX

transwit

Simple Loop Antenna for RDF

A paper illustrating a loop antenna for direction finding on 2 meters.

by Bob W1RPQ

RDF Antenna

FT-891 Project Build

A comprehensive g0-box with Raspberry pi interface to do FT8 and other modes in the field - exemplified with the Yaesu FT-891.

by Bob W1RPQ

FT891 Go Box