Phillipe Cantin writes:
So you want to two HC-05 modules to automatically connect together, as soon as they’re powered up and with zero code? Well this is your lucky day since this can be done using the AT+BIND command.
Let’s do this thing!
For this, you will need:
1 Arduino (I’m using UNO)
2 HC-05 modules
Arduino IDE (I’m using version 1.0.5-r2)
HC-05 Bluetooth link with zero code - [Link]
Dilshan Jayakody published a new build, a VHF Aircraft radio communications receiver:
This is simple radio receiver project which is capable to receive aviation radio voice signals which are transmit between 118MHz to 138MHz in AM (A3E). We got initial idea of this project by reading Sverre Holm’s (LA3ZA) article about “cheap VHF receiver project”. Like LA3ZA’s original article this project is also based on Samsung’s KA22429 FM radio receiver IC.
KA22429 is low voltage FM radio receiver system developed by Samsung for portable radio receivers and as described by Holm’s it can push into VHF region by changing few values in its original circuit. In this project we redesign the schematic and PCB with some of those changes and now it can directly tune into aviation band with minimum number of adjustments.
VHF Aircraft radio communications receiver - [Link]
I’ve for some time now wanted to do more RF design. Although I have taken some RF design courses, I haven’t actually made a single RF design before. But you can’t learn without doing and inspired by the MIT coffee can radar designed by Gregory Charvat, I figured that building a radar should be a doable project that would offer some challenge while also having some real world use.
The simplest radar is a continuous wave Doppler radar, which continuously transmit a constant frequency signal. This signal reflects from a moving target and Doppler shift causes reflected signal to change frequency. This reflected signal is then received and mixed with the transmitted signal. Mixer product is the difference of the frequencies which is proportional to the speed of the target. This kind of radar is very simple to make, in fact there are even some children’s toys. Unfortunately it can’t detect the range of the target and isn’t that exiting.
6 GHz frequency modulated radar - [Link]
by Colin Jeffrey @ gizmag.com:
In the world of electronic components, there are many devices out there that do their job well and reliably, but are almost never heard of – even though they may be vital to equipment that plays a role in our technology-driven lives. The radio frequency (RF) circulator is just such a device: it has simply done its job as a nondescript box of gubbins buried in radio communications systems, quietly directing radio frequency signals to the places they should go. Now researchers at the University of Texas have given the RF circulator a makeover. Not only is the new prototype smaller, lighter, and cheaper, it’s also claimed to be easily adapted to different frequencies on the fly, which is something the old style circulator cannot do.
New RF circulator to run rings around old technology - [Link]
by Sam Freeman and Wynter Woods @ makezine.com:
This simple hack turns your Raspberry Pi into a powerful FM transmitter! It has enough range to cover your home, DIY drive-in movie, a high school ball game, or even a bike parade (depending on the stragglers).
PiFM software not only boldly enhances the capability of your Pi, but does so with nothing more than a single length of wire. This hack starts with the absolute minimum you need to run a Raspberry Pi — an SD card, a power source, and the board itself — and adds one piece of wire. It’s the coolest Pi device we’ve ever seen with so few materials.
Raspberry Pirate Radio - [Link]
RaysHobby build a project called RFToy:
it’s an Arduino-compatible microcontroller board for interfacing with radio frequency (RF) modules, such as the popular 433/315MHz transmitter/receiver, and the nRF24L01 transceiver. The RFToy has a built-in ATmega328, USB-serial converter (CH340G), 128×64 OLED display, three buttons, and a coin battery holder. Programming is done in Arduino through the on-board mini-USB port. It has three sets of pin headers to directly fit RF modules, and an audio jack to output RF receiver signals to a computer’s sound card. Using RFToy you can build a variety of projects involving RF modules, such as remote control and wireless sensors.
Introducing RFToy, an Arduino-compatible gadget for radio frequency modules - [Link]
Among the signals below 550 kHz are maritime mobile, distress, radio beacons, aircraft weather, European Longwave-AM broadcast, and point-to-point communications. The low-frequency converter converts the 10 to 500 kHz LW range to a 1010 to 1550 kHz MW range, by adding 1000 kHz to all received signals. Radio calibration is unnecessary because signals are received at the AM-radio’s dial setting, plus 1 MHz; a 100-kHz signal is received at 1100 kHz, a 335-kHz signal at 1335 kHz, etc. The low-frequency signals are fed to U1, a doubly-balanced mixer.
Transistors Q2 and associated circuitry form a Hartley 1000-kHz local oscillator, which is coupled from Q2’s drain, through C8, to U1 pin 8. Signals in the 10 – 550 kHz range are converted to 1010 – 1550 kHz. The mixer heterodynes the incoming low-frequency signal and local-oscillator signal. Transistor Q3 reduces U1’s high-output impedance to about 100 Ω to match most receiver inputs. Capacitor C15 couples the 1010 – 1550 kHz frequencies from Q3’s emitter to output jack J3, while blocking any dc bias.
Inductor L6 couples the dc voltage that’s carried in the rf signal cable from the receiver/dc adaptor. The dc voltage and rf signals don’t interfere with one another; that saves running a separate power-supply wire, which simplifies installation at a remote location. Capacitors C14 and C13 provide dc supply filtering.
Low-Frequency Converter - [Link]
RFID keyboard emulators are able to significantly simplify tracking of goods.
“Replacement” of a keyboard in a form of an RFID module connected to a USB port works very simply – UID of every tag, which will appear in its range will send to a computer – the same way as if we typed it in by a keyboard. SL040A also enables to choose, whether we want the reader to send only data, or also a „CR“ character after every UID (as if an Enter key was hit). It means, that if we already have a software to type in open (for example Excel), the reader itself will fill the cell with data and move the cursor to another cell. SL040A is even able to read data (not only UID) from Mifare tags.
SL040A is also interesting by one feature – on a request from our company SOS electronic, the producer started to produce also the black version SL040A black. Thanks to the above-standard close relationship with the producers, we´re able to supply you even various special customized versions.
Detailed information will provide you the SL040A user manual.
SL040A will load it to you directly into a table sheet - [Link]
by TheSignalPathBlog @ youtube.com:
In this episode Shahriar takes a close look at an HP/Agilent 5347A 20GHz Frequency Counter and Power Meter. This defective unit does not provide any frequency information from Input 2 which is rated to operate up to 20GHz. Before the teardown and repair attempts, the principle operation of the instrument is reviewed.
The properties of a Step Recovery Diode (SRD) is presented along with the theory and practical aspects of generating a frequency comb. The heterodyne architecture of the frequency counter is explained in detail with the mechanism of detection and calculation of the input frequency.
During the teardown of the unit the synthesizer board, motherboard, power meter reference board and the main RF assembly are shown. The schematic of the synthesizer board and the RF board are also described. The defective component is identified and examined under the microscope. The slides for this episode can be found at The Signal Path website.
Teardown, Analysis and Repair of an HP/Agilent 5347A 20GHz Frequency Counter & Power Meter - [Link]
RaspWristRadio – Wearable Personal FM Radio Station - [Link]