More to come...

Who is ZL2PD?

For anyone remotely interested in the person behind this website, a few more details can be found here.

Email ZL2PD?

Links to other websites:

Logging the Changes:

24.10.23 Part 2 of Condor series added

23.10.23: Condor transceiver series started

1.2.23 Added details on the local radio club's adventure when producing a short run of SC+ kits

20.1.23 Added the 99 channel SugarCube-Plus RF oscillator

25.5.22: Added PW CTCSS encoder and a new CTCSS encoder emulating hard to find CTCSS chips

11.1.22: Added the variable RF attenuator and a range of additional HEX files for my four tone CTCSS encoders

7.7.21 : Added the 9-band modular keypad/encoder controlled VFO

10.6.21: Added SC+4/SC+16 and SC+99, the CEFR fuse reset/erase tool, the TR-105 story, and details on making small nH inductors 

27.11.20: Added details of a very low cost multitone CTCSS encoder

12.11.20: Added thoughts on CTCSS Decoders and PE RF signal generator builder notes

27.4.20: Added NiteOwl Torch and a pair of simple CTCSS Encoders

31.1.20: Added smaller 64x32 OLED equipped SugarCube VFO

6.12.19: Added enhanced software for the SugarCube VFO/BFO

10.11.19: Added the portable keypad Si5351a test generator.

10.7.19: The miniature SugarCube VFO is added to the website.

30.05.19: Added details about my AM/FM/CW scanning signal generator published in Silicon Chip magazine.

5.04.19: Added tuning lock function to Single Band si5351a VFO project.

27.02.19: Updated and improved software for SWR Meter project.

17.11.18: Added PVM, VFO PCB, I2C LCD mods, uBitx mic, MKARS80 VFO, plus minor changes.

12.8.18: Small project update, minor changes.

19.11.16: Some minor maintenance updates and corrections here and there.

20.8.16: Updated several pages, added new Nighthawk, aviation rx, xtal checker, cardboard LC meter and 8-digit counter box projects.

7.3.16: Added source code files and a bit more info to the multi-feature si5351 VFO, and added details of a second si5351 VFO

28.2.16: The ZL2PD si5351a VFO, GPS frequency reference, Li-Ion battery monitor, CS2000 signal generator were added to the website

15.9.15: The OBD-2 speedometer and a digital QRP SWR meter were added to the website

18.6.15: Soldering stations, four dot clock and soldering iron cleaner added

17.3.15: In which Andrew described how Yahoo sent his email to another continent!!

30.10.14: Lots of new projects added


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.

I usually have a number of large and small projects ready to be published. All I have to do is find the time to write them up for the website. So check back here periodically to see the latest additions.

What's New?

I'm very excited to introduce this series of web-pages about the tiny Condor 2 channel handheld Search and Rescue 1W HF QRP SSB transceiver and the modifications required to convert it for ham use on the 80m and 40m HF bands. Designed and made in New Zealand, the 2-channel Condor entered service during the 80's. It's a novel design using the phasing SSB method(!!) Gradually decommissioned and replaced by higher power handheld transceivers, some Condors remain in use today.

The first part of this series introduces this transceiver. Other pages, to be uploaded here just as quickly as I can document the details
, will describe the modifications required to convert the Condor for amateur radio use on 80m and 40m. Part 2 describes the special version of my SugarCube-Plus VFO. I'll also describe a compact antenna tuning unit (ATU) and SWR bridge (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 is some updated information on the legacy AWA TR-105 portable 5W HF SSB transceiver. The 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.

I've recently obtained one for conversion to 80m and 40m amateur radio VFO operation. I will be adding the details on the modifications required, hopefully very soon. Stay tuned!!

I've finally completed the 99 channel version of my set of fixed-frequency SugarCube+ oscillators. Any channel can be programmed from 5kHz to 290MHz. And it's super-compact, of course, and incredibly easy to build.

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.

My local amateur radio club decided to build SugarCube+ VFOs as a club project. I was asked to help arrange the initial run of ten kits. It ended up being quite a journey. That seems to be the rule with kit production.

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.

Practical Wireless in the UK published details of my latest CTCSS encoder in their June 2022 issue. The details are all there, including software, PCB layouts, etc.

On this module, the CTCSS tone can be selected with a 6 or 8-way DIL PCB switch. The article also described its installation in a legacy Dick Smith 2m synthesised FM transceiver.

I compiled software for the ATtiny24 or Tiny44 or Tiny84 (You choose!) and the HEX program, PCB layout and supporting files can be downloaded from PW as well as  from here on my website too.

I was asked if one of my CTCSS encoders could replace an obsolete CTCSS encoder chip that was used in a legacy ham transceiver. These devices, primarily made by CML, MX-Com, Panasonic and Seiko, were often used by Kenwood, Yaesu, Icom and Trio in their FM transceivers. Some can be very hard to find now.

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.

Variable RF attenuators are used many applications. I use them for bench tests and in test equipment such as RF signal generators.

This is a simple low cost variable RF attenuator. There's an HF version using discrete thru-hole parts, and a compact SMD version, shown here, which works from 3 to 500MHz (and beyond, with care) with an attenuation range of over 60dB.

You can find all the information here....

CTCSS is widely used in ham radio, just as its been for many decades in professional two-way radio systems. Having looked for a suitably small and cheap CTCSS encoder to help restore several old VHF transceivers around here, I ended up designing three different high performance CTCSS encoders. They all share the same tiny single-sided PCB.

You can read more about two of these CTCSS encoders here...

NEW: FIVE different CTCSS tone sets are now available to you to download.

Here's a new easy to build multiband modular Si5351a VFO with keypad and rotary encoder tuning. It's a design for those who look at my SugarCube VFO designs and say “I couldn’t ever build something that small!”

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...

If you need an RF oscillator for your transceiver for a few fixed frequencies, or an alternative to expensive crystals for a radio restoration, or maybe you want a multi-channel RF oscillator with lots of fixed frequencies, then one of the three new versions of my SugarCube-Plus may be exactly what you need.

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.

A number of my designs use all of the pins on the microcontroller. If you have to reprogram those ATtiny chips, you must first reset the chip fuses. If you build my new channel-based SugarCube-Plus, you'll need one of these. It resets the fuses in any 8-pin ATtiny85 back to factory-default condition.

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

Building circuits at VHF and UHF frequencies usually requires making a variety of small inductors. These typically lie in the 5 to 100 nano-Henry range.

I tried using Web-based information and calculators to make these inductors but that proved inaccurate (Surprise!). So, I returned to first principles. I made a number of inductors and carefully measured them.

I then produced a graph as a guide for making such inductors. Others may find this information useful so I've provided the details of my measurements here.

When I designed several compact CTCSS encoders in early 2020, I thought that would be the end of it. But requests for details of my multitone CTCSS encoder I mentioned briefly in the text have just kept on coming ever since. I just quickly tried that extra software in passing while designing the simple encoders.

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.

Designing a reliable compact cost-effective fully-featured software-based CTCSS decoder that actually works over a wide range of audio levels and in the presence of noise is a serious technical challenge.

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...

Silicon Chip magazine published two more of my designs in their September 2020 issue. Both are illustrated on the cover.

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.

Practical Electronics magazine in UK published one of my designs in their June and July 2020 issues - An AM/FM/CW HF and VHF scanning signal generator. Previously published in Silicon Chip magazine in 2019, it covers from 100kHz - 50MHz and 70MHz-120MHz, or 150 MHz with reduced output..

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

We've had some of our extended family staying with us during the COVID-19 crisis lockdown here in New Zealand. Our eldest grandson needed a light for bedtime reading to avoid waking up his younger brother.

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...

If you are REALLY squeezed for space in your design, here's the latest addition to the Sugarcube VFO family. Following a request for an even smaller display, I've now added a version for the tiny 0.49" 64x32 pixel OLED displays. All of the features, including user-programmable settings, are retained.

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...

I've just developed new software for the SugarCube VFO, a Si5351a based VFO with dual VFOs and quadrature outputs. Not only have I added dual BFOs and improved tuning, but thanks to a suggestion from Eric, ZL2BMI, I've added user parameter programming. And all of this still fits (just!) inside the 8k memory of the little 8-pin Atmel ATtiny85. Cheap, easy to build and use.

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

This handheld compact portable 3-output HF/VHF Si5351a RF test oscillator started out as a basic Si5351a software test platform but it quickly grew as features were added. The choice of keypad and tuning knob make it easy to use.
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....

I've developed what I think is the smallest Si5351a VFO complete with a fully functional OLED display. My SugarCube VFO measures just 20 x 20 x 12mm excluding the modest 23mm (0.91") OLED graphic display, encoder and pushbuttons. It features dual VFOs with quadrature outputs, plus a BFO/CIO output, operation to nearly 300MHz, and a neat bright clear frequency display to 1Hz. I describe a VHF FM receiver application, too.

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

Previously Added:

My compact digital SWR meter for QRP (low power) transceivers and transmitters weighs in at just 50 grams. It's powered from a single AAA battery and uses a bright, easy to read, OLED graphics display.

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.

PkDVMMy si5351a VFO designs have proven to be incredibly popular. Many kits for my designs have been sold by others over the internet, unsurprisingly without crediting me as the designer.

To help you build the single band VFO/BFO, I've design a
PCB for my single band VFO/BFO. You can use a Midas I2C LCD or the larger cheaper compatible Chinese I2C LCD. You can find the layout here which has been recently updated to fix some parts labelling errors.

I finally got some time to build my MKARS-80 80m SSB kit transceiver which I purchased some years ago. It used a PIC as a frequency counter to control the analog VFO using the 'huff and puff' method.

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...

The Nighthawk 40m CW transceiver. This tiny 10W-capable transceiver is a SW-40+ clone kit available from China. It arrived after a mix-up with my order for an SSB kit. I built it anyway. But then nothing worked. Nothing.

Fortunately, I've managed to fix all of the (many) design errors in this kit. I'm really delighted to have it running. The whole story is 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...

Other Popular ZL2PD Designs:

This is my compact aviation band receiver. I added a channel-based control board to a widely available aviation band receiver kit. Then I packaged it in an unusually shaped 3D-printed enclosure to make it look more interesting. Even the knobs are printed.

Inside the box, an ATtiny84 generates the DC tuning voltage for the varicap on each of 10 programmable channels using an unusually fast 16-bit DAC. The ATtiny also drives a small 7-segment LED display to show the channel number. A single button  select any of 10 programmable channels. All the details are here....

My si5351 dual output VFO/BFO has more features than I can list here, and remains very popular. Over 3,000 downloads of the software now! It uses a Nokia 5110/3310 graphics LCD and it covers all of the usual amateur radio bands. Add more if you wish. The VFO's low power consumption (Just 30mA at 3.3V) makes it suitable for QRP, and it's cheap to build. The details are 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.

My single band si5351 dual output VFO/BFO also remains popular. It uses fewer than 20 parts including an 8-pin ATtiny85 and an I2C alphanumeric LCD display. An S-meter/RF power meter display is built-in too.  Same low power consumption.

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 much more detail.

And you can download most items too, if you wish. (Something not there? Just email me and ask. Some material is not immediately available because of rampant unattributed sales of downloaded material from my website over the past few years by some individuals and companies)

To date, the details and designs here on my website include:

Elsewhere on the ZL2PD website ...

A suite of three different designs for temperature controlled soldering stations, with a detailed design for the most compact unit. It uses a single 8-pin ATtiny25 microcontroller and not much else, and it is packaged in a compact 3D-printed enclosure, also of my own design.

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

For those looking for something a little different, here is a Four Dot Clock which uses just four cheap LEDs (Four dots of light, if you will) to display the time. It's surprisingly accurate. I only adjust it now about once every six months.

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.

Here are the details of an earlier design for a compact digital RF signal generator using a Cirrus Logic CS2000 chip. It's compact, with everything inside a small 3D-printed case. It generates a 3.3V squarewave output from 1.5 to 160MHz (although the specs on that chip claim it is limited to 75MHz) and draws less than 20mA from a 4 - 15V DC supply.

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...

Example image - aligned to the right

I think I'll give up predicting what will appear here next. Stuff on my list includes:  

A model train controller with sound effects (Not for me, it's for my grandsons, really!)

An interesting HF SSB receiver with a few differences

A low power DC boost converter to replace a commercial module, and

A truly compact LC meter

And there are lots of other projects still waiting in the pipeline. 

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.

Example image - aligned to the right