The ZL2PD Amateur Radio and Homebrew Electronics Website
A prototype remote controlled microprocessor-based automatic antenna tuner under development on the workshop bench at ZL2PD


An example of how a simple idea ("I think I'll build my own automatic antenna tuner!") got quickly tossed together using bits and pieces I had close to hand.

Now all I need to do is add that final feature and get around to finishing off that software...
This website describes a variety of projects related to my hobbies of amateur radio and electronics, including:
Circuit diagrams (i.e. schematics)

Descriptions  - How they work, what they do

PCB layouts (sometimes)

Construction details (if required)

Software (for any designs which use microprocessors)

Other details which may be helpful in duplicating these designs, or for building your own variations of my projects.
Other Useful Links:
Harry Lythall's Homebrew Homepage
PA2OHH Webpage
Hans Summers Homebrew Site
Kazuhiro JF1OZL Homebrew Site
Break In : One-Eyed Frequency Counter
A tiny frequency counter which fits in your top pocket. This counter uses the Atmel AT89C2051 microprocessor (and you can use most other 8051 family micros instead) to count and display frequencies up to
65 MHz             
More information and Software download is here.....
My Info:
Name:  Andrew
Silicon Chip DDS VFO Project:
Email: ZLtwoPD at
(Replace the word with the numeral and the 'at' with the usual symbol)
Silicon Chip DDS VFO - Extra Details and Software Download

Published in
Silicon Chip magazine in March 2008, this compact VFO with a graphics LCD display is designed for use in amateur radio receivers and transceivers.

The 8051-based software is available for free download

IT'S HERE! : How to change the DDS VFO software to suit transceivers with different IF offset frequencies - I also added a few more extras to download at the bottom of the DDS VFO project page.
Click Here to Find Out More About ZL2PD
KN-Q7 Transceiver and Related Projects:
ZL2PD Builds the KN-Q7 40m SSB Transceiver

This QRP transceiver was lots of fun to build. But the limited information in the kit led me to write what I think is a better set of kit building instructions. They might help you too.

And then there was that schematic wasn't all that I redid that as well, and fixed up a couple of minor errors in the original.

Read more here....
KN-Q7 Accessories and Extras

I've designed and built a few accessories to help operate my new
KN-Q7 transceiver. These include:

AC power supply (12V @ 2A)
An antenna tuner, and
A tune-up aid

In addition, I wanted to find a way to
interface a cheap computer microphone-headset with the KN-Q7.
General Projects:
The Hunt for the Elusive Varicap

I've been slowly building an SSB transceiver and I needed some varicap diodes for several sections of the design. These are hard to find parts
but some work has shown that well known components -
high power zener diodes - can be used with excellent results.
Simple LED Frequency Counter

This 8051-based HF frequency counter uses an old 87C751 chip and a 74HC4040 to reach up to 40 MHz. Simple, but effective.
Audio Signal Generator

A battery powered CMOS-based audio sinewave test oscillator which has been in use around the ZL2PD workshop for more than 10 years.
Mini Metal Detector

Built in a hurry to locate nails in the timber wall frames in my house.
No-IC Audio Amplifier

When I couldn't find a suitable audio amplifier IC in my junkbox, this simple transistor circuit was the solution..
Wide Range HF Signal Generator

This HF signal generator can cover up to 60 MHz and is easy to build.
Digital HF Antenna Analyser

Software downloads for this project are located on this webpage. This project, a microprocessor-based HF antenna impedance meter with LCD display of impedance and VSWR, was described in New Zealand's "Break-In" ham radio magazine in early 2005.
Inside Compact Switchmode Power Supplies

I often use modified "wall-wart" switch mode power supplies and discarded celphone chargers in my projects. Here's more information on what's inside some of those units (Schematics!)
How to Modify Small Switchmode Power Supplies

Since the output voltages of those little switchmode chargers or power supplies seldom matches the voltages I need for my projects, here's how I modify them to suit my exact requirements.
Building a Small Variable Switchmode Power Supply

I needed a really lightweight variable power supply to take with me on my travels. A modified compact switch mode power supply did the trick!.
Electronic Sandglass
Originally published in Elektor Electronics in June 1995, this is an electronic version of the old fashioned eggtimer and uses a Philips 87C751 microprocessor and LEDs to simulate falling sand .
CMOS Keyer Rebuild
Years ago, I build an iambic automatic morse keyer, the Accu-Keyer. It died suddenly, so I rebuilt it. This time, I used a simple design with just two low current CMOS ICs and a few transistors.
Check back for more projects soon...
Some of my other projects which have been published include:
One-Eyed Counter  - Break-In (New Zealand amateur radio magazine) May/June 2008

This pocket-sized RF frequency counter was originally designed for use during trips away from home. Capable of operation up to 80 MHz, it is also suitable for use on the workbench.
TuneAid  - Break-In  March/April 2008

This audio oscillator is constructed into a small plastic box along with an electronic timer allows an SSB transmitter and accessories such as an antenna tuner to be adjusted prior to operation.
Simple Wide Range HF Oscillator  - Break-In  Sept/Oct 2007 (pages 8 - 9)
A 48 - 85 MHz VCO tuned by a multiturn resistor is mixed with a fixed 48 MHz crystal oscillator. Filtered and amplified, the result is a variable oscillator which tunes 0.4 - 35 MHz in a single sweep.
Digital Antenna Analyser - Break-In  Jan/Feb 2006 (pages 4 - 7)

LCD readout of frequency and VSWR and covering from 1.6 to 33 MHz. Battery powered, it uses the 87C552 microprocessor, one of the 8051 family of microcontrollers from Philips, and some analog circuitry.
Analog Antenna Analyser - Break-In  Sept/Oct 2005 pages 4 - 7)

Displays measured antenna VSWR on a small direct reading meter in three ranges across the 3 to 30 MHz HF band. It uses only CMOS and basic opamp parts and is powered by a 6V NiCd battery. it contains an optional three digit frequency counter and may also be used as a simple signal generator.
Simple VHF FM/AM Radio - Silicon Chip magazine, December 2002 (pages 86 - 90)

A classic two transistor VHF superregenerative receiver covering 70 - 180 MHz using a piezo-sounder from a greeting card as the receiver's speaker.

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