“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 […]

Transistor radio series: the AF power amp

Vasily Ivanenko @ QRPHB writes, “I sought a low distortion, single supply, AF power amplifier for my transistor radios. I’ll present my experiments, some musings, test equipment and a reference to some wonderful books & their wise author. Sadly, some amateur radio receiver builders diligently craft their RF stages, but skimp on the PA audio stage. […]

Transistor radio series – The 7 MHz scratch synthesizer

Vasily Ivanenko has written up documentation on his 7 MHz synthesizer project: Above — All 4 boards were built in re-purposed Hammond boxes. A PIC-based counter sits on top of the offset mixer. I build modular gear and this allows modification and fosters experimentation. When I build a final transistor radio receiver, I plan to […]

Simpleceiver Plus version 2 SSB transceiver

An update on Pete Juliano’s (N6QW) Simpleceiver project we covered previously: Version 2 — What is it? V2.0 is the Simpleceiver Plus SSB Transceiver Architecture with the following changes: A GRQP Club 9.0 MHz Crystal Filter is used in place of the homebrew 12.096 Four Pole Filter. This gives the advantage of acquiring the matching […]

A two channel SI5351 signal generator

DuWayne Schmidlkofer has a nice write-up on building a two channel SI5351 signal generator: After getting the sketches written for the SI5351 board written to support multiple display types, I decided I need to write one more. Now that Pete is moving the Simpleceiver to a single conversion super-het, I will have to worry about […]

Teardown and repair of an Agilent 53152A 46GHz microwave frequency counter

Agilent 53152A 46GHz frequency counter teardown and repair from The Signal Path: In this episode Shahriar investigates a faulty Agilent 53152A 46GHz frequency counter. The instrument does not power on and shows no sign of internal voltage presence. Teardown of the instrument reveals a large PCB where all analog and digital circuity is contained. The power supply […]

Tutorial, experiments and teardown of a 77GHz automotive FMCW radar module

Tutorial, experiments and teardown of a 77GHz automotive FMCW radar module from The Signal Path: In this episode Shahriar explores the principle operation of automotive FMCW radars. Thanks to a donated automotive radar module, various components of the system can be examined and explored. The PCB reveals three die-on-PCB ASICs responsible for generating and receiving 77GHz […]

Shirt Pocket Transceiver with the Si5351 and OLED

Pete Juliano’s (N6QW) Shirt Pocket Transceiver with the Si5351 and OLED display: In 2011 I fulfilled a dream of building a shirt pocket sized QRP SSB transceiver. Well actually I built two of them and the second was a diminutive 2″ X 4″ X 2″. Both used through hole components –so no cheating with SMD. […]