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 […]
Category Archives: RF
Compact Si5351 based SDR
Ray Ring has written an article detailing the build of his mini SDR radio using FV-1 Audio processor and Si5351: This is a revised version of my FV-1 based SDR. I replaced the CS2100 clk generator with the Si5351 clk generator. The Si5351 has some advantages over the CS2100, namely you can generate quadrature clks […]
“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 […]
Ham Radio HT turns CW (Morse) transceiver
Ham radio HT CW transceiver project from WhiskeyTangoHotel.com: Really not much explanation needed; just connect as shown above. This project uses an electronic keyer, but a simple straight key/oscillator combo could also be used. Oh… and you will also need to know Morse Code.
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, […]
WBR-Oscar regen receiver
A nice write-up on Sheldon’s (N6JJA) version of N1BYT’s WBR regenerative receiver: This article is broken into two parts. First comes the “Oscar” preselector/preamplifier. As I said, I intended it to be either part of the overall receiver or used as a standalone where desired. The second part deals with the WBR upgrades. Both designs […]
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 […]
N6QW Heathkit SSB transceiver
Pete Juliano, N6QW, has a nice build log on his newest version Heathkit 40M SSB Transceiver: What are you thinking — I am not trying to break any world record? My XYL asked me that question today — why are you building another rig? Followed up by a snide comment that I had so many […]
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. […]
MFJ-1708SDR transmit/receive switch for SDR receivers
Here’s a demonstration of the MFJ-1708SDR transmit/receive automatic relay switch from YouTube channel HamRadioConcepts . Here is an interesting device, for use with your SDRplay or other SDR dongle for receive. You can share your current antenna with your 100 watt HF rig and an SDR for receive.
The ‘$20 Bill’ DC receiver
Steve’s (a.k.a N8NM ) ‘$20 Bill’ DC receiver: If you follow Bill, N2CQR’s SolderSmoke blog, you know that he’s working on a simple DC receiver of his own, which, along with his aversion to using the magic chips, served as inspiration for this rig, which is how it got it’s name: $20 is my guess […]
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 […]
Homemade 6 GHz FMCW radar
Henrik Forstén has a nice build log on his newest version of this homemade 6 GHz FMCW radar: Frequency Modulated Continuous Wave (FMCW) radar works by transmitting a chirp which frequency changes linearly with time. This chirp is then radiated with the antenna, reflected from the target and is received by the receiving antenna. On […]
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 […]