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Archive for the ‘RF’ Category

A limited attenuation high-pass filter for the KiwiSDR

Monday, July 16th, 2018

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...

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

Tuesday, June 19th, 2018

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...

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Transistor radio series: the AF power amp

Wednesday, June 6th, 2018

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...

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MFJ-1708SDR transmit/receive switch for SDR receivers

Friday, March 30th, 2018

https://www.youtube.com/watch?v=EcVDKTZMaM8 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.

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The ‘$20 Bill’ DC receiver

Tuesday, February 27th, 2018

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...

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Transistor radio series – The 7 MHz scratch synthesizer

Wednesday, November 29th, 2017

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...

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Simpleceiver Plus version 2 SSB transceiver

Thursday, November 2nd, 2017

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...

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A two channel SI5351 signal generator

Thursday, October 12th, 2017

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...

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Homemade 6 GHz FMCW radar

Friday, September 29th, 2017

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...

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

Wednesday, August 9th, 2017

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...

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

Friday, June 2nd, 2017

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...

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Practical RF filter design

Monday, March 20th, 2017

[embed]http://www.youtube.com/watch?v=1sq8Cvju2Oo[/embed] 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,...

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Shirt Pocket Transceiver with the Si5351 and OLED

Monday, January 16th, 2017

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...

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Forty-9er Shield

Friday, December 23rd, 2016

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...

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CTCSS fingerprinting: A method for transmitter identification

Friday, December 9th, 2016

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...

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Scalar Network Analyser Jr

Tuesday, December 6th, 2016

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...

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Input filter and preamplifier – Jupiter modular receiver

Tuesday, October 18th, 2016

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....

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Raspberry Pi RF frequency counter

Tuesday, October 11th, 2016

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...

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Posted in R-Pi, RF | 3 Comments »

VHF Frequency Counter with PC Interface

Wednesday, September 7th, 2016

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...

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Breadboard line driver module

Tuesday, August 23rd, 2016

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...

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