QRP-Labs Filter Adapter for NanoVNA

Cabe Atwell writes on Hackster about a RF filter adapter was made using some spare parts and lowpass and bandpass filter kits:

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QRP-Labs Filter Adapter for NanoVNA

Check out Lex Bolkesteijn’s new project constructing a QRP-Labs filter adapter for NanoVNA with some spare parts and lowpass and bandpass filter kits. The NanoVNA is a tiny handheld Vector Network Analyzer (VNA), which accomplishes both high-performance and portability. Besides working as a vector network analyzer and antenna analyzer, this build utilizes it as a filter tuner.

A current work in progress, last updated in mid-June, it was developed using a double-sided PCB, two SMA chassis, and a header cut in two to form a filter holder that enabled the use of the NanoVNA to test and tune the filters as required. The filter kits themselves include the double-sided PCD along with silkscreen, solder mask, and through-hole plating, as well as the capacitors. Both are the same size, and so require no adjustments to the filter holder.

Although the filter has four pins, five holes are drilled in the PCB base of the filter holder using a perforated PCB for spacing. The fifth hole allows for a via to connect the top and bottom layers. With some soldering, the via, SMA chassis parts, and headers are connected to the base. In a few steps that, everything is set up to connect the filter to the NanoVNA.

The NanoVNA should be calibrated before use, and in the documented project, this was done with an experimental calibration tool. When calibrating as close as possible to the adaptor, it’s not possible to use the calibration standards. The calibration tool was made with another PCD, with holes drilled for vias and two 100 Ohm SMD 1206 resistors.

A design, complete with CAD files for the casing, is also included for those who are unable to mill PCBs by hand. This uses a 3D-printed casing and custom-ordered PCBs to serve as the adapter. Simplifying the manual work required in the design, even more, the most recent custom PCB ordered includes built-in calibration options. The 3D-printed base looks spiffier than the hand-milled PCBs and requires no additional PCB for calibration.

For anyone interested, the bill of materials, CAD files, and a step-by-step with images are freely available on Bolkesteijn’s blog.

QRP-Labs Filter Adapter for NanoVNA

Build Your Own RF Lab: Scalar Network Analyzer

Whitney Knitter writes on Hackster about a simple scalar network analyzer that can be controlled by a Raspberry Pi for measuring the frequency response of filters and networks:

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Build Your Own RF Lab: Scalar Network Analyzer

With the popularity of wireless applications having become such a staple in the hobbyist community, the need for RF testing capabilities in the hobbyist realm has also increased. Anyone familiar with traditional RF test equipment knows that it is expensive. But challenges like this are what bring out the engineering creativity in this community. Steven Merrifield designed and laid out his own simple scalar network analyzer (SNA) using just a few IC chips. SNAs are handy for testing the frequency response of filters or networks.

A scalar network analyzer is used to test the amplitude of a device’s frequency response by outputting a sine wave sweeping over a certain frequency range (bandwidth) then measuring the amplitude of each incremental output frequency.

Thus if you directly connect the sine wave output of an SNA to its measurement input, then it will read a flat line of the same amplitude for each incremental output frequency of the sweep:

When a device is connected to the SNA, the amplitude of the sine wave at each frequency after going through the device will reflect the device’s frequency response over that bandwidth.

Merrifield’s design accomplishes an SNA’s functionality via implementation of a DDS Synthesizer chip, an ADC, and a logarithmic amplifier chip. The AD9850 DDS is responsible for outputting the sweeping sine wave while the AD8307 logarithmic amplifier conditions the signal input into the SNA for the log of the signal’s envelope before passing it on to the ADC for digitizing. A second AD8307 also conditions the output of the DDS and outputs it to a second channel of the ADC so that it can be used in software for compensation of any variations on the DDS’s output due to the effects of various loads of devices being tested.

The ADC outputs its digital measurements via an I2C interface to a GPIO header that matches the Raspberry Pi’s GPIO header pinout, but any desired MCU or FPGA could be used. The source code Merrifield wrote is in C, making it easy for porting across different platforms.

Check out Merrifield’s project logs here. He linked his PCB layout on OSH Park if you’re interested in ordering it and putting one of these together for your own lab!

Build Your Own RF Lab: Scalar Network Analyzer

QRP-Labs filter adapter for NanoVNA

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QRP-Labs filter adapter for NanoVNA

I had a few QRP-labs lowpass filters and bandpass filters kits laying around and because I had nothing better to do this afternoon, I fired up the soldering station and assembled them. After that they need to be tested and tuned.

Owning a NanoVNA for a few months now (and hardly use it because for antenna stuff i use my RigExpert AA-600), I decided to use the NanoVNA for tuning the filters. So from some pieces out of my junkbox (a piece of double sided pcb, 2 sma chassis and a header cut in 2) I build this simple filter holder allowing me to test and tune the filters to my requirements.

Adding the 3D printed base plate, hooking it with my NanoVNA.

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Doing the calibration routine.

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And ready for testing.

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As expected like the previous design. But now no aditional PCB for calibration.

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Can only say that the purple on yellow looks cool 🙂

For those who want a adapter, checkout my ForSale page.

QRP-Labs filter adapter for NanoVNA

Raybeacon 1.4 is out

The rayBeacon by Mike M. Volokhov is a Nordic nRF52 on-the-go development kit:

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Shared Project: Raybeacon 1.4

The Raybeacon is full-featured nRF52 based wearable, ultra-low power, multiprotocol development board designed for variety of embedded applications. Due to modular design, the device can be used to build your own production-ready appliance with minimal hardware modifications.

Key features include:

  • Coin sized – the board is only 25 mm in diameter
  • Works from a single CR2032 / CR2025 3V button cell
  • Nordic nRF52 high-end multiprotocol SoC supporting Bluetooth 5.x, Bluetooth mesh, Thread and Zigbee; of your choice:
    • nRF52833: Cortex-M4F 64MHz, 512KB flash, 128KB RAM, Bluetooth® 5.1 Direction Finding, 105°C temperature qualification
    • nRF52840: Cortex-M4F 64MHz, 1MB flash, 256KB RAM, Bluetooth® 5.0, ARM TrustZone® CryptoCell cryptographic unit
  • Automotive grade BOM components – ready for harsh environment
  • 2 x tactile buttons IP67
  • 1 x RGB LED
  • 1 x infrared LED (850 nm) 0402 size
  • Socket for NFC flex antenna, compatible with Nordic FPC antenna and Liard 0600-00061. Can be configured as extra 2xGPIO.
  • Programmable through SWD port (removable Tag-Connect socket, on-board solder pads)
  • 1.27mm pitch 2×4 receptacle to connect custom extension boards:
    • 6 x GPIO ports
    • 1 x 12-bit ADC input
    • pass-through VDD and GND pins
  • 2.54mm pitch 1×8 pin header for fast breadboard prototyping; can be reused as 1.27 to 2.54 adapter
  • USB interface (on-board solder pads)
  • Minimal fabrication cost due to simple, two-layers only design

For detailed description, including information on custom boards and source files, please refer to the project repository on Bitbucket. Also, feel free to share your thoughts, or submit a request for a new slice or report an issue!

 

Raybeacon 1.4 is out

Low-cost Amateur Radio SDR Receiver

writes on the Tindie blog about a DSP-based radio that can receive SSB:

DSP_radio_featured

Low-cost Amateur Radio SDR Receiver

As an amateur radio operator, I am always keeping an eye out for cool new radio-related things to tinker with. Hams have a long tradition of building and designing their own radios, and it’s great to see this still happening in the digital era. This DSP-based radio can receive SSB (single sideband) over almost the entire amateur HF band. This band spans from 1.9 MHz (also called 160 meters) all the way up to 28 MHz (10 meters) and everything in between.

This is a great radio for portable use. Paired with a small CW (continuous wave, the mode used for Morse code) transmitter, it would make a great QRP set for those who love low-power Morse communication. Bandwidth can be adjusted from 500Hz to 4kHz, which is perfect for CW as well as digital modes. The designer specifically designed it to be used with the extremely popular new digital mode FT-8, and it indeed fits the specifications very well. It could also be used for many other digital modes, including PSK, RTTY, JT65, and many more! The audio output can be wired directly into any PC — even a Raspberry Pi — to enable digital reception modes.

Low-cost Amateur Radio SDR Receiver

Junebug Chipsat dev board

Brad Denby designed this chipsat dev board for low-power, embedded computing in space that is one of the winners of the Take Flight with Feather contest:
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Junebug

Chipsat development board for low-power, embedded computing in space

Junebug is a cutting-edge addition to the Feather ecosystem. It acts as a development board for chipsats – an emerging class of space system. It offers unique support for batteryless, intermittent computing. The FPU, DSP instructions, and storage space allow advanced sensor data processing with ML. Junebug is easy to manufacture, with parts selected to allow hand-assembly.

The schematic, PCB design, Gerber and Drill files, bill of materials, and other files are provided in the linked GitHub repository.

Junebug Chipsat dev board

Penguino Feather SAMR34 LoRa Dev-Board

Orkhan AmirAslan on Hackaday.io has created a RAK4260 based, Feather styled LoRa dev-board:

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Penguino Feather SAMR34 LoRa Dev-Board

This is a SAMR34 based LoRa dev-board with all the necessary components for fast prototyping. It’s a successor of my previous Penguino RF module and Feather breakout design ( https://www.tindie.com/products/16985/ )The new design uses the RAK4260 module from @RAKWireless and improves on some aspects, such as USB Type-C, RGB LED, user button, battery protection & voltage supervision, and optional flash & per-provisioned secure element IC pads.

Background:

About a year ago, after I first saw SAMR34 System in Package (SiP) in 2018 Electronica I couldn’t find a module for it and I took up the challenge for myself to build one myself. Then sharing first renders with the Twitterverse it gathered quite a bit of interest and I started selling couple over at my Tindie store. At the time I named the project TinyLoRa but for legal reasons I had to change it to Penguino.

Specs:

  • ATSAMR34J18 LoRA System-in-Package (SiP) based RAK4260
  • ARM Cortex M0+ MCU & SX1276 LoRa Radio
  • 256KB Flash, 40 KB RAM
  • Max Tx Power: +20 dBm; Max Sensitivity: -148dBm; Rx Current: 17mA (typical)
  • Frequency Range: 862 to 1020 MHz (DS values)
  • Deep Sleep Current: ~1 μA (module only)
  • Li-Po battery charging IC
  • RGB user LED, Battery Charge Status (red) and Power (blue) (w/ cut-off jumpers)
  • 3.3V low Iq LDO (~1 μA)
  • Low-voltage battery cut-off supervisor IC (3V Vbat cutoff)
  • USB Type-C connector with protection/filtering circuit
  • 0.75 A resettable fuse
  • Voltage divider for Vbat monitoring (w/ cut-off jumpers)
  • SMA and u.FL antenna connectors
  • 10-pin SWD programming header
  • Dimensions: 2 in. x 0.9 in. (50.8 mm x 22.8 mm)

Penguino Feather SAMR34 LoRa Dev-Board

DC26: overview of the DC503 party badge

From Nisha Kumar:
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An overview of the DC503 party badge as seen at DefCon 2018

Hi! My name is Nisha, and I made a party bangle for my friend, Miki, to take with her to DefCon25. It was my first fully-formed electronics project and it posed some interesting challenges due to its unusual form factor. You can read about my experiences with that project here.

Soon after DefCon25, I was approached by r00tkillah to make over a 100 of something similar for the DC503 party at DefCon26. The plan was to combine the power of the BMD-300 SoC by Rigado used in the Wagon Badge from the previous year with my Neopixel bangle form factor. We would call it “The Banglet” and it was going to be awesome.

banglet_shell_500

In passive mode, the banglet’s LEDs light up when detecting nearby Bluetooth devices. The number of LEDs that are lit correspond to the number of BT devices detected and their colors are based on each device’s mac address.

DC26: overview of the DC503 party badge

iceRadio SDR project

Software Defined Radio (SDR) project by Eric Brombaugh:
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iceRadio

This is a test prototype for experimenting with Software Defined Radio (SDR). It is composed of several boards that are described in detail elsewhere on this site:

Combined with suitable firmware and FPGA design, these boards comprise a receiver capable of capturing 20kHz of signal from DC to over 1GHz, demodulating it with a variety of formats and driving high-quality audio.

iceRadio_system.png

Tuner

RF input from the antenna can optionally be tuned down from VHF/UHF frequncies to an IF frequency in the HF range before passing to the ADC.

ADC

Raw HF or downconverted VHF at an IF of 5MHz is digitized to 14-bit resolution. The maximum input signal allowed without exceeing the range of the ADC puts the 0dBfs point of this system at -10dBm in 50 ohms. The ADC runs at 40MSPS with a resolution of 10 bits, providing approximately 60dB of dynamic range and 20MHz of bandwidth which places the quantization noise floor at about -70dBm.

FPGA

From the ADC, data passes into the FPGA. This is an iCE5LP4k part which provides 20 4kb RAM blocks and 4 16×16 MAC blocks which are essential for the DSP required for the downconversion. In the FPGA the ADC data is pre-processed to a sample rate appropriate for the MCU. Figure 2 below shows the primary components of the FPGA design.

iceRadio_fpga

The C and Verilog source code is available on GitHub:

emeb/iceRadio

iceRadio SDR project

An Especially Tiny And Perfectly Formed FM Bug

It used to be something of an electronic rite of passage, the construction of an FM bug. Many of us will have taken a single RF transistor and a tiny coil of stiff wire, and with the help of a few passive components made an oscillator somewhere in the FM broadcast band.

via An Especially Tiny And Perfectly Formed FM Bug — Hackaday

An Especially Tiny And Perfectly Formed FM Bug