Welcome
Welcome to my website. This site describes some equipment and circuits that I've designed and built. Many are related to amateur radio, but there are also some test equipment projects, kit builds, and other things that I have designed. I'd like to claim it's all been done to a plan, but that's not really the case. Development of this material tends to follow a fairly random process around here.What's New?

This modification uses my new “SC+M” Si5351a-based SugarCube-Plus VFO. It's very easy to build because it uses thru-hole components, well, apart from the Si5351a SMD chip that lies at it's heart. You can read about the SC+M here.
We're planning to convert a number of these radios at our radio club. To help, I've also designed some test and calibration tools which you can read about here too.

All of the other features are retained. The encoder can generate any of the 50 (!!) industry-standard CTCSS. The output is a very precise, stable and low distortion sinewave. It uses a standard rotary encoder, and the selected tone is shown on the tiny OLED display. All of the details may be found here.

I've designed a two-tone audio oscillator upgrade for my "DITA" precise 1kHz audio oscillator. This allows this ultra-simple audio oscillator to also generate a two-tone audio pair for testing SSB transmitters.
Two jumpers allow selection of either the original precise 1kHz DDS-generated audio tone or any one of three three sets of two-tone audio pairs.
Practical Wireless published my design in their February 2025 issue.
You can download the software and the PCB files from here.

This was designed to provide a precise 1kHz oscillator for over-the-air transmitter frequency checks. However, there are many other applications for it.
You can download the software and/or the PCB files and/or the industry-standard STL files to make the 3D-printed enclosure here.

It's possible to create a kit for this if there is sufficient interest (Email me!). It won't be very expensive. All of the parts required are easy to find and quite inexpensive.

The first part of this series introduces this transceiver. Next, Part 2 describes the special version of my SugarCube-Plus VFO for the Condor. The detailed description of the modifications required to convert the Condor for amateur radio use on 80m and 40m is here in Part 3 Condor Conversion. I'll also describe a compact antenna tuning unit (ATU) and SWR bridge shortly (The Condor is designed for 75 ohms!) as well as some alignment and testing accessories.
The Condor replaced the much larger TR-105 SAR transceiver, an HF radio I've previously described here.

Here are some details on the legacy AWA TR-105 portable 5W HF SSB transceiver. The (much) older TR-3 AM transceiver is often mistaken on the internet for the TR-105 because they are both yellow. Any day, I expect to see a photo of a giraffe in yellow pyjamas incorrectly identified as a TR-105!
Many years ago, I was supported the maintenance and operation of about 150 Search and Rescue TR-105 radios. TR-105 radios were also used by Mountain Radio Service in New Zealand for many years. You can read about the TR-105 here.

The 64x32 or 70x40 pixel OLED shows the channel selected with the rotary encoder. You can also define the "start" (wake-up) and "last" channel which your SC+99 uses.
Frequencies are user-programmable via a spreadsheet. A mouse click generates the EEP file for uploading to the SC+99's EEPROM. The details are all here.

It all turned out successfully, I think, and you can find the information here including the detailed kit-building instructions. You can get details of a new PCB I designed to hold all the front panel parts as well as a 3.3V regulator.
I've also added links on this new page to all the other SugarCube pages on my site.

After some detailed study, I've designed and tested a further version of one of my CTCSS encoders. This encoder allows you to select one of four different tone schemes in the software. This allow this design to replace the encoder functionality of some of these increasingly rare and often expensive CTCSS chips. You can find the details here.

You can read more about two of these CTCSS encoders here...
NEW: FIVE different CTCSS tone sets are now available to you to download.

This design uses a few low-cost modules to make construction easy. I've also created an Excel spreadsheet to allow you to enter the band edge frequencies for each of the nine bands (or memories) supported by the VFO, as well as the start-up frequency for each band. You can precisely set the reference crystal frequency, too.
It's all described in detail here...

The 20 x 20mm SC+4 and SC+16 deliver up to four and sixteen fixed programmable RF frequencies anywhere from 5kHz to 290MHz! There's an optional OLED channel display, too. The channel digits can be easily seen from across the room.
You can enter your frequencies using my new spreadsheet. It can save the data to EEPROM in Atmel's EEP format on your hard drive, too. The details are here.

Using widely available parts and running from a USB port or wall wart, it's a very low cost solution when you need to reset ATtiny chip fuses. It also clears the flash and EEPROM memory to allow the Lock fuses to be reset, too. It works on tiny13, tiny25 and tiny45 devices as well. Details can be found here.

Well, I've now documented two versions of my multitone CTCSS encoder. The first uses the same tiny PCB as the basic CTCSS encoders, while the second version features a slightly larger PCB, an improved filter, and a portable battery powered enclosure. Both feature an OLED display. You can find all of the details here.

CTCSS decoders used to be widely available at modest cost. Now, they are hard to find (and expensive!) with CTCSS integrated into almost every new transceiver and handheld.
So is a combined CTCSS decoder/encoder ('dencoder') modulae of any use to anyone these days? Here's a background to designing CTCSS decoders and some possible applications and solutions...

The first design is a blinking night-light 'lighthouse', an ideal project for those starting out in the electronics hobby or a grandparent looking for an inexpensive project to build with grandchildren.
The second of my designs is a compact 'shirt pocket' sized battery powered digital audio oscillator using an 8-pin ATtiny85. The design features a standard rotary encoder which uses just one I/Opin on the ATtiny85.
All of the details are available from the Silicon Chip website.

Some information is described here on this page about solutions to a couple of problems experienced by some builders.

I had an old NiteOwlTM gathering dust at the back of a shelf. Some basic design issues led to its rejection a decade earlier. But where there's a need, there's a way!
I converted this old near-useless incandescent reading torch into a highly efficient LED torch. You can read more about it here...

The dual-band capable SugarCube software all still runs inside the 8k memory of the little 8-pin Atmel ATtiny85. All of the details of this version can be found here...

The details about the updated software for the SugarCube VFO is here....

Powered by a single 18650 Li-ion cell and recharged from a standard USB charger, its low power consumption allows it to operate for several months of intermittent use before needing recharging. It weighs just 170 grams (6 ounces).
It doesn't have an attenuator or the modulation features on my all-mode Silicon Chip RF signal generator (See below). However, it can generate AM modulation!
You can read about it here....

Parts cost? Less than $US10. You'll find all the details about my little SugarCube VFO here....
Popular Pages:

Some new 0.96" OLED displays didn't work correctly with the original software. Bob ZS6RZ brought this to my attention helped test the revised software. Thanks, Bob!
ATtiny45 and ATtiny85 versions are available as well as the larger 1.3" OLED displays with their (similar, but different) SH1106 controllers.

Naturally, I decided to upgrade it with a new version of my single band si5351a VFO/BFO. This version uses a cheap Arduino Nano along with the kit's standard 16x2 LCD. My design features selectable tuning steps, an S-meter and RIT. (More features might be added later...) It's also still in the rough prototype stage but the details of the new design are here...

This photo shows an electrically heated towel rail. I've designed an AC delay timer for mine. It saves power and avoids the need to nag my family members about turning it off every morning. I know - A 'First World' problem.
It is a solution which may have other applications where switching AC loads is required. It uses one of the 8-pin Atmel processors, The details can be found here...

Kits have been supplied by others via the Internet (without crediting me in any way for the hardware design or the software). That's why it may look familiar to some.
And thanks to Cristi YO3FLR, there's a PCB layout available in the Download section on my VFO's webpage.

There's also an updated PCB layout available, too.
The details are here...
Wait...There's More! - How to Navigate the ZL2PD Website
You'll find the complete list of my published designs down the left hand side of this page. Just click on any item to take you to that design. Schematics
and other drawings are to be found all over the site, as are photos.
Want to see the details close-up? Then just "right-click" on the image
or schematic or whatever with your mouse. Chances are, you'll now be able to see that stuff in much
more detail. And you can download many items too, if you wish. Is something not there? Just email me and ask. Some material is not immediately available because of rampant copying and subsequent sales of downloaded material from my website over the past few years by some individuals and companies. All without permission or reference back to me. If customers later had questions, most just told their customers to email me!
To date, the details and designs here on my website include:
- Several transceivers (For some reason, these have been mostly other people's designs! Must address that soon...)
- Accessories for these transceivers (DDS VFOs, ATUs, SWR meters, etc )
- (Lots of) Oscillators and test equipment
- Switchmode power supplies
- A temperature-controlled soldering iron, and
- Some family-related designs (An unusual LED clock, an electronic sand-dial timer, a binary thermomenter, a Christmas tree...)
Elsewhere on the ZL2PD website ...

(Right-click the image for a closer look or visit my web page)

More interestingly, perhaps, is the fact that, unlike most clock designs you might have seen, this one does not require another chip to actually do the timekeeping. The clock's ATtiny45 does all that, and more.

It's really the result of a tale of woe and misfortune, but the circuit works... More details here.
Of course, all of the other designs are still available to browse and build, each listed over to the left in the index. Help yourself!
New Designs... Well...
A really compact LC meter (Actually, I've designed three or four of these so far...)
Stay tuned...
The Legal Stuff
You use the information published on these web pages at your own risk!
You
may use the information
provided here for personal or educational purposes but you may not
reproduce it in any form or use this information for any commercial
purpose without
first obtaining written permission from the copyright holder.
There is no warranty or guarantee, either expressed or implied,
covering any information of any kind which may be available from this
website or any correspondence associated with this information,
or that designs and information provided on this website are
free from patent or intellectual property rights of the author or third
parties.
Should the information contained on this website be used by any party,
that party shall by using the information provided be deemed to take
complete responsibility for all risks and liabilities associated with its use and hold the
author of this website harmless in the event of any claim, loss,
liability or expense associated with any such use.
The rights of copyright over the contents of this website, unless
otherwise noted, are claimed by Andrew Woodfield ZL2PD.