The rumors for RFM12B’s end-of-life two years ago seem to have been highly exaggerated now and the popular RF module is still available in abundance. HopeRF has introduced a pin-compatible upgrade, the RFM69CW. The module itself offers improved sensitivity and range compared to the RFM12B (+30%) at the cost of increased power consumption, making it probably a good choice for the receiving end (RFM2Pi), and probably less suited for low power battery operated nodes. The new module supports RSSI for those interested in measuring it.
The new module is more power hungry, and simply replacing a RFM12B on the RFM2Pi v2 or a Funky v3 with it didn’t work; The boards browned out so I had to swap C4 and C7 on the RFM2Pi with 10uF caps and populate the 0805 10uF on Funky v3’s boost regulator circuitry to get it to work. I’ll ship the boards with these refinements from now on so that they are compatible with both the RFM12B and RFM69CW.
Using RFM69CW instead of RFM12B - [Link]
In this video Craig demonstrates his custom DIY RFID smart lock project:
The goal of this project was to design an inexpensive rfid door lock which could be opened via smart phone, and have all activity logged w/o utilizing any 3rd party servers or cloud hosting.
Custom DIY RFID smart lock - [Link]
Microchip Technology Inc., has announced the first in a series of modules for the LoRa technology low-data-rate wireless networking standard. The system is designed to allow Internet of Things (IoT) and Machine-to-Machine (M2M) wireless communication offering a range of more than 10 miles (suburban), a battery life of greater than 10 years, and the ability to connect millions of wireless sensor nodes to LoRa technology gateways. The 433/868 MHz RN2483 is a European R&TTE Directive Assessed Radio Module measuring 17.8 x 26.3 x 3 mm and with 14 GPIOs to provide connections and control for a large number of sensors and actuators.
The RN2483 is also supplied with the LoRaWAN™ protocol stack, allowing connection with the LoRa Alliance infrastructure—including both privately managed local area networks (LANs) and telecom-operated public networks—to create Low Power Wide Area Networks (LPWANs) with nationwide coverage. This stack integration also enables the module to be used with any microcontroller with a UART interface. The RN2483 also uses Microchip’s simple ASCII command interface for easy configuration and control.
Microchip LoRa Network Module - [Link]
by Colin Jeffrey @ gizmag.com:
For the first time in history, a prototype radio has been created that is claimed to be completely digital, generating high-frequency radio waves purely through the use of integrated circuits and a set of patented algorithms without using conventional analog radio circuits in any way whatsoever. This breakthrough technology promises to vastly improve the wireless communications capabilities of everything from 5G mobile technology to the multitude devices aimed at supporting the Internet of Things (IoT).
World’s first fully digital radio transmitter built purely from microprocessor technology - [Link]
One of the simplest digital modulation schemes in current use is the Frequency-shift keying (FSK). FSK is similar to Frequency Modulation or FM except that the modulating signal is a binary pulse stream that varies between two discrete voltage levels rather than a continuously changing analog waveform. In FSK, two discrete frequencies are used to represent the binary digits 0 and 1.
The heart of the circuit consists of two Wien-bridge oscillators built using a dual op amp LM1458, for the two frequencies. The two frequencies are enabled corresponding to digital data using two switches in HEF4016BP. The control lines of these switches are logically inverted with respect to each other using one of the switches in HEF4016BP as an inverter, so as to enable only one oscillator output at a time. The digital bit stream is used to control the analog switches as shown. Since the switching frequency limit of HEF4016BP is 40 MHz, high-data rates can be easily accommodated. This method comes in handy when expensive FSK generator chips are not readily available; also, the components used in this circuit are easily available off the shelf and are quite cheap.
FSK was originally used to transmit teleprinter messages by radio (RTTY) but can be used for most other types of radio and landline digital telegraph. Currently, FSK is commonly used in Caller ID and remote metering applications.
Low-cost FSK Generator – [Link]
By David Szondy @ gizmag.com:
A global economy brings many benefits, but it also makes international terrorism extremely difficult to combat. With more goods passing through the world’s shipping terminals and airports than ever before, hunting explosives with large, static detectors or teams of inspectors armed with detecting devices and reagents is a bottleneck that increases the chances of evasion. To help US counterterrorism efforts, GE has developed RFID stickers that act as wireless, battery-free explosives detectors that can be placed almost anywhere.
GE RFID tech turns stickers into explosives detectors - [Link]
An active bandpass filter can be wide-band or narrow-band as needed. If the higher -3dB frequency divided by the lower -3dB frequency is greater than 1.5 then a wide-band filter is needed. An effective and easily understood active wide-band filter can consist of merely a low-pass and high-pass filter in series. The high-pass and low-pass filters are share the same design, with resistors and capacitors in the same positions but reversed for each type of filter.
Bandpass Filter - [Link]
Kenneth made a 2m low pass filter and wrote a post on his blog detailing its assembly:
I’ve been playing with the DRA818V modules that have been making quite a stir in the amateur radio world at the moment. I haven’t gotten one on a spectrum analyzer yet, but I have reason to believe that it will require a low pass filter to be RF legal. I’ll write more about that once I get a look at it, but figured I’d first built myself a low pass filter in case I need it (if not for these modules, but some other VHF project in the future).
My process for building a low pass filter went as follows:
Select the type of filter and cutoff frequency desired
Look up normalized coefficients in the ARRL Handbook
Divide these coefficients by the cutoff frequency
Convert the inductances into turns on some core and capacitors into the nearest values
Build the filter
Designing and building a 2m low pass filter - [Link]
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]