or
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...
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.
65 MHz More information and Software download is here.....
(Replace the word with the numeral and the 'at' with the usual symbol)
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 here.
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.
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 clear....so I redid that as well, and fixed up a couple of minor errors in the original.
Read more here....
I've designed and built a few accessories to help operate my new
KN-Q7 transceiver. These include:
An 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.
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.
This 8051-based HF frequency counter uses an old 87C751 chip and a 74HC4040 to reach up to 40 MHz. Simple, but effective.
A battery powered CMOS-based audio sinewave test oscillator which has been in use around the ZL2PD workshop for more than 10 years.
Built in a hurry to locate nails in the timber wall frames in my house.
When I couldn't find a suitable audio amplifier IC in my junkbox, this simple transistor circuit was the solution..
This HF signal generator can cover up to 60 MHz and is easy to build.
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.
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!)
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.
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!.
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 .
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.
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.
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.
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.
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.
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.
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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