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. […]
Category Archives: RF
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 […]
Practical RF filter design
Craig writes, “RF filter design is a piece of cake these days thanks to computer design and simulation tools. But actually realizing the simulated filter response in the real world can be a completely different matter! This video provides an introduction to practical RF filter design by building, testing, and tweaking a 137MHz bandpass filter […]
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. […]
Forty-9er Shield
m0xpd writes: I’ve been tinkering with a quick lash-up of Wayne Burdick, n6kr’s famous ‘Forty-9er’ receiver, implemented on an Arduino shield and tuned by one of my DDS systems. Regular readers will remember how I tried running my Kanga / m0xpd Sudden-inspired receiver shield under the control of the new DDS on the Internet of […]
CTCSS fingerprinting: A method for transmitter identification
Oona Räisänen from Absorptions wrote an article about experimenting with CTCSS fingerprinting: Identifying unknown radio transmitters by their signals is called radio fingerprinting. It is usually based on rise-time signatures, i.e. characteristic differences in how the transmitter frequency fluctuates at carrier power-up. Here, instead, I investigate the fingerprintability of another feature in hand-held FM transceivers, […]
Scalar Network Analyser Jr
M0xpd documented his experience building DuWayne’s Scalar Network Analyzer Jr: DuWayne’s baby uses an AD9850 in one of our familiar modules to generate RF, under the control of an Arduino NANO. You can read on DuWayne’s blog how the SNA Jr is the descendant of earlier experiments in which an Si5351 was used as the signal […]
Input filter and preamplifier – Jupiter modular receiver
Vasily Ivanenko blogged about his input and RF preamplifier build: Above — Build of the input and RF preamplifier stage. I put in a 0 or 6 dB attenuator right at the input. That’s double-sided Cu+ board with copper vias joining the 2 surfaces intermittently and also at crucial ground points. Project info at QRP HomeBuilder blog.
Raspberry Pi RF frequency counter
A Raspberry PI RF frequency counter project from Scott Harden, that is available on GitHub: Raspberry PI RF Frequency Counter with Python Interface. The RF signal clocks a 32-bit counter (SN74LV8154) connected to a 16-bit IO expander (MCP23017) accessable to the Raspberry Pi (via I²C) to provide real-time frequency measurements from a python script. More details […]
VHF Frequency Counter with PC Interface
Scott has published a new build: This is the general idea behind how this frequency counter works. It’s so simple! It’s entirely digital, and needs very few passive components. sn74lv8154 is configured in 32-bit mode (by chaining together its two 16-bit counters, see the datasheet for details) and acts as the front-end directly taking in […]
Breadboard line driver module
Scott from SWHarden has published a new build: Line driver chips are one of my go-tos for quickly amplifying digital signals because they’re so fast to drop in a breadboard and they provide a strong output with very high impedance inputs and need no external components. Individual buffer of the integrated chip can be paralleled […]
40 meter XCVR size of an business card with 1 watt output, 7.000 to 7.150 MHz coverage
A business card size homebrew 40 meter XCVR project from Ray Ring: I tweaked my previous XCVR design to use push button tuning and made the board layout extremely compact. I improved the side tone injection to be absolutely perfect – not too loud, full break in and no clicks. I went ahead and integrated my switch […]
Progress on the LDMOS amplifier
An update on Pete’s (N6QW) LDMOS amplifier project we covered previously: The real value of the breadboard test system is that it enables you to find/discover things that were not so obvious. Currently I have the Start & Stop buttons wired to the Arduino. I also have all six of the Low Pass Filter relays […]