An important part of Amateur Radio is that we have the ability to design and build our own radio equipment. However, getting started in this activity takes a ton of skills that seem to be hard to learn. One good way to jump start this process is to build a radio from a kit. This allows the operator to learn proper build techniques, while following the lead of a tried an true design. A typical starting point is to build a receiver with a low power transmitter. We’ve put together a kit that should let those that wish to take this step, succeed. We’ve chosen a small 40 meter 1/2 watt CW (morse code), circuit that will transmit, and receive on 7.030 MHz. This frequency is in the Technician band, so any licensed amateur operator can transmit and receive using this device. These QRP radios will allow the user to send and receive CW signals, with a good antenna, that could reach 120 miles.
The SCARS Homebrew team has put together the parts, and created this documentation to help you build these radios. In addition, there’s a team of us that will help you gain the skills needed to build them. And, if something doesn’t work right, we’ll be there to help you diagnose the trouble. These kits currently run about $10, and can be obtained from club officers.
SCARS Pixie Kit
These kits are currently available for $10 from any SCARS officer. The SCARS kits are made up of the following pieces:
- Main circuit board and case kit, which includes most of the circuit pieces, case parts – This is the real core of the kit, and contains all of the resistors, transistors, capacitors, connectors, and more. This kit also has 6 lexan pieces that will be used as a case for the radio. eBay details
- 12 volt battery connections, a 7.030 MHz crystal (to replace the 7.023 MHz Extra only crystal that comes with the main kit), some 3.5 mm jacks for the audio, and the CW key, an antenna connector to mate the BNC jack to a common F connector, and a BNC dummy load. eBay details
- 9 volt battery connectors – The typical use case will be to power this radio with a 9 volt transistor battery. The additional 9 volt battery connector will be installed ‘after’ the full wave bridge, to allow better receive performance on a 9 volt battery. eBay details
- 3 pin SIP socket – This SIP socket will have the center pin trimmed, so you can slide the crystal in, and out, for future changes. eBay details
- 7.030 MHz crystal – The kit comes with a 7.023 MHz crystal. This frequency is in the “Extra Only” portion of the 40 meter band. This replacement crystal will let Technician and General operators transmit in their own portion of the band. eBay details
- Headphone with 3.5 mm plug – These earphones will let you hear the received signals. eBay details
- 3.5 mm plug for a CW key – This will let the operator connect a straight key to the Pixie radio. Pressing the key will turn on the transmitter. eBay details
- BNC female jack to an F connector – This will let the user connect an antenna using inexpensive, low-loss RG-6 coaxial cable. A simple dipole can be connected for better reception. eBay details
- BNC dummy load – This device will let the user transmit without damaging the transmitter. Should the user simply want to send signals to an short wave receiver, or to another local transceiver. eBay details
Installation and User Operation
The following Pixie User Manual can be used to help the build process of the Pixie radio. Using the circuit diagram should help the user figure out where each of the pieces and parts should go. Remember to dry fit the pieces to make sure you know you’ve got them set properly, before you solder them in tight.
A number of skills are required to create this build.
- Resistor color code – You’ll need to know how to read the colored bands on the resistors, to determine their value. Knowing their value will help you select the proper resistor to put in the proper slot. There’s a copy of the resistor color code in the Pixie User Manual.
- Reading a schematic – You’ll need to learn the schematic circuit drawing, and figure out which component goes into which holes on the printed circuit board. This design only has a limited number of parts, so this should be pretty easy. The circuit is in the Pixie User Manual.
- Capacitor number code – You will need to know how to read the capacitor values and make sure you select the proper capacitor for insertion into the board.
- Soldering – You’ll need to use a small soldering iron to solder the components to the bottom of the printed circuit board. Once you’ve applied a bit of heat to the board, and the component, you’ll add some solder to the joint. The solder will flow between the two pieces, and they will be connected, both electrically, and mechanically. For more information, please see the SCARS soldering page.
- Clipping the stray leads – You’ll use a diagonal wire cutter to clip the stray leads off the bottom of the board, once they’re securely soldered. Make sure you’re careful to hold the soon to be loose end, so it doesn’t fly across the room.
There are only a few small hand tools that are needed to finish this project. These will be available at ‘work nights’, or upon request from members of the SCARS Homebrew team:
- Soldering Iron
- Diagonal ‘side’ cutters
- Small pliers
The Newport County Radio Club has done something similar with this circuit, and has created some great documentation. This NCRC_PixieOperation presentation explains how the circuit works, and what each part of the circuit does.
CQ February 2018 Review
Our good friends at CQ magazine have jumped on board with this project kit, and have an article about this project in their February 2018 Issue – Pixie Transceivers Construction. KA8SMA has purchased a couple of these devices, and has some good construction comments, and an upgrade that includes a variable capacitor to let you move the frequency a bit.
In 1982, George Burt GM3OXX described the original circuit for the radio now known as the Pixie. More historical information is available in The_Sprat_Pixie_File.
Pixie Build Review
Amateur Radio Operator 4Z4TJ has created a nice little review of the Pixie kit, and lists his thought in this Pixie Build Review.