High efficiency 4V supply QRP amplifier

Low voltage, high efficiency QRP RF amplifier project @ circuitsalad.com This is an example of a high efficiency QRP transmitter designed to work at very low supply voltages (3v-5v). It can produce 2 watts a 4 volt supply @ 70% efficiency. It uses small, inexpensive switching mosfets. The primary requirement for these mosfets is low […]

A different power source for field ham radio operating

Gwen, NG3P, has been working on a power source project for field ham radio operating: We’re coming up on a confluence of two things: Nice weather, and relaxing of the Covid-19 lockdowns in much of the United States. This means more hams leaving their home shacks and taking their operating to the field. For some, […]

An experimental HF 6-band SSB transceiver

Peter (DK7IH) has been working on HF 6-band SSB transceiver: Part 1: Project Basic Outline Presentation Part 2: The Oscillators (VFO, LO and Testtone Osc.) Part 3: The Microcontroller (ATMega128) Part 4: Bandswitching Logical Circuits Part 5: Measuring Transceiver Data Part 6: The Receiver Part 7: The Transmitter Part 8: Transmit/Receive Switch Unit Part 9: […]

FIREO – a low power SSB/CW tranceiver with its unique speech processing

Kang.K.P.S. writes: “FIREO” (Pronounced FIRE-O), is basically a bit of non-conventional QRP (low power) SSB/CW transceiver design in which speech compression is implemented using FM limiter circuit. This unique approach of speech processing increases the effective average transmitted power and thus it improves on the signal strength reports at the receiving end. Consequently this technique […]

“Cigarette Pack”- 14MHz SSB QRP Micro-Transceiver

Peter Rachow (DK7IH) built a 14MHz SSB QRP Micro-transceiver into a cigarette packet size case: This article describes the “Cigarette Pack” SSB QRP transceiver” for 14MHz that I first had mentioned some months before. Recently, when taking it from the shelf, the transceiver dropped to the floor and was severely damaged. This lead to serious […]

A transmit converter (and amplifier) for 630 and 2200 meters

KA7OEI has a great write-up on building a transmit converter for 630 and 2200 meters: As the name implies, a transmit converter takes another frequency – such as that produced by a conventional HF transceiver – and converts it to another frequency.  In my case I use an FT-817 – a low-power (5 watt) all-mode, […]

A simple 8-channel receiver voting controller for enhanced repeater coverage and usability

KA7OEI has written an article detailing a simple 8-channel receiver voting controller: To simplify things, this voting controller sits in “front” of an ordinary repeater controller, taking the audio and COS inputs from the various receivers and outputting a single audio and COS signal. If the repeater system in question uses subaudible tones, it is […]

Automated channel switching with Motorola GM3x0

Florian Wolters wrote an article on automated channel switching for POCSAG/DAPNET transmissions on MMDVM system: With the integration of POCSAG/DAPNET features into the MMDVM/MMDVMHost I came to think about if it would be possible to combine an MMDVM repeater/HotSpot with a DAPNET tranmitter. The advantage in Germany is that there is a single coordinated frequency […]

A limited attenuation high-pass filter for the KiwiSDR

KA7OEI published a new build: One of the issues common with using a broad-band, direct-sampling SDR (software-defined radio) like the KiwiSDR is that of overload by strong, low-frequency signals, such as those on the AM (mediumwave) broadcast band – but there’s another problem that should be considered as well:  The high generally-high signal levels at […]

Tutorial: Setting up a low cost QRP (FT8, JT9, WSPR etc) monitoring station with an RTL-SDR v3 and Raspberry pi 3

A detailed tutorial on how to set up a cheap QRP monitoring station using an RTL-SDR V3 and a Raspberry Pi 3 from rtl-sdr.com This tutorial is inspired by dg0opk’s videos and blog post on monitoring QRP with single board computers. We’ll show you how to set up a super cheap QRP monitoring station using an […]