In this section you will find detailed description of my homemade amateur radio radio equipment, mainly two-way radios for single sideband modulation (SSB). Also known as “QRP” radios. But also a lot of microcontroller-related material. Please keep in mind that the designs are free for non-commercial use and for educational purposes. Any commercial exploitation would violate this copyright. Thank you!
This article is about some sort of rebuilt of my first handheld SSB QRP transceiver (aka “Walkie-Talkie”).
For the short wave enthusiastic radio amateur they are practical from 14Mhz and above and offer nice working opportunities along with outdoor activities such as hiking, biking or boating. In this article a portable radio for 14MHz will be described. Due to the fact that it uses a DDS oscillator (AD9835) as main VFO and a ladder filter for SSB generation, the combination of VFO and LO makes it possible to re-design the circuit for other bands, e g. the 18, 21, 24 and 28 MHz amateur frequencies.
A proven and reliable circuit has been chosen. This includes a single conversion superhet receiver, DDS VFO, a crystal controlled local oscillator (LO) and a three stage linear amplifier in the transmitter section capable to supply 5 watts PEP to the antenna. The radio can be used as a “Walkie-Talkie” with in-built rod antenna and external or attached battery pack. It also might be employed as a stationary QRP-transceiver with base antenna.
By the way: For this project a printed circuit board (PCB) is available!
A simple way of decoding NMEA/GPS-signals with an STM32F411-MCU will be described. Software in Embedded C also will be discussed with a special stress on proper USART baudrate calculation.
This project replaces the analog 2-tone oscillator described in a former project. Equipped with 2 AD9850 DDS ICs and an STM32F microcontroller it provides much more precise setting and variation of the frequency of the 2 audio tones used for testing the linearity of an SSB transmitter.
(Bands: 3,5MHz, 7MHz, 14MHz, 18MHz, 21MHz)
Oscillators, Microcontroller (MCU)
(Bands: 1.8MHz, 3,5MHz, 7MHz, 14MHz, 21MHz, 28MHz)
- Basic outline
- Band Switching
- Measurement units
- T/R Switching
- Circuit, Schematic and Discussion
- Software source in Embedded C
50 to 70 watts output power
- Basic outline
- Overview/Block Diagram
- Receiver Front End, 1st Mixer
- IF Amplifier
- Productdetector, Audio Section, AGC
- Transmitter (article missing 🙁 )
- Receiver Improvement
A compact handheld QRP SSB transceiver for 14 MHz