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9 Nov 2014


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]

13 Oct 2014


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]

11 Oct 2014

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]

6 Oct 2014


RaspWristRadio – Wearable Personal FM Radio Station - [Link]

23 Sep 2014


Shawn McCombs blogged about his DIY Arduino RFID card door lock system 100 cards build. [via]

DIY RFID card lock system - [Link]

23 Sep 2014

example__86477.1409204603.1280.1280by shop.ciseco.co.uk:

The Wireless Inventors Kit for the Raspberry Pi (RasWIK) is an exciting and affordable addition to the Raspberry Pi. RasWIK demonstrates that with our leading edge technology anyone (and we mean anyone) can build wireless sensors and actuators , you do not need huge experience, a degree or even any tools. We show you even how to connect the devices you build to “the Internet of Things” (IoT) service providers such as Xively.

Getting started is just 5 simple steps:
1. Insert the preconfigured SD card to your Pi
2. Plug in the Slice of Radio to the GPIO connector
3. Turn on the Pi
4. Power the XinoRF development board
5. Lauch the Python based example application on your Pi
Thats it!……..you are now past step one of your journey to wireless nirvana :)

RasWIK – Raspberry Pi Wireless Inventors Kit - [Link]

22 Sep 2014


by elektor.com:

A press release from the University of Southern California describes a novel transmission technique which can achieve very high data rates. The research led by Alan Willner of the USC Viterbi School of Engineering does not use a single carrier to send information but instead combines independent radio beams using a ‘spiral phase plate’ that twists each radio beam into a unique and orthogonal DNA-like helical shape. The receiver untwists the beams and recovers the different data streams. “Not only is this a way to transmit multiple spatially collocated radio data streams through a single aperture, it is also one of the fastest data transmission via radio waves that has been demonstrated,” Willner said.

Twisted RF beams achieve 32 GB/s - [Link]

22 Sep 2014


Ondřej Karas of DoItWireless writes:

 If You are interested in LED driving through RF, this article would be interesting for you. I tested own PCA9634 breakout board for this chip and wrote simple low level driver for IQRF TR-52D module. Next week, I am going to publish PC application for comfortable operation with that.


Wireless LED driver with PCA9634 - [Link]

19 Sep 2014


HOPERF modules enable to gain a wireless data transfer or remote control of devices simply and without excessive costs.

A company, which specializes over a quarter of century on a given segment usually has experience and production capacities to develop and produce quality components. This is also a case of company HOPERF Micro-electronics and moreover – thanks to high production capacities the prices of their products are very attractive. HOPERF produces RF chips themselves, as well as read-made RF modules usable for virtually any application requiring a wireless control or data transfer, for example: remote keyless entry (RKE), control, security systems, telemetry, voice and data communication, control of processes and many others.
HOPERF modules offer besides a great price also a very high flexibility of usage. In contrast to many “fix-set” modules, RF modules HOPERF usually offer very wide possibilities to dynamically adjust many parameters, like for example: FSK/ OOK/ ASK modulation, possibility to work in a wide frequency range including free ISM bands 315, 433, 868 and 915MHz, while all main RF communication parameters are programmable.

In our stock can be found for example:

  • RFM65CW-433S2 and RFM65CW-868S2 – 433/868 MHz FSK receivers. RFM65CW offers a unique possibility to use narrow-band and also wide-band communication modes. RFM65CW is optimized for a low power consumption while maintaining high sensitivity.
  • RFM68CW-433S2 and RFM68CW-868S2 – 433/868 MHz FSK transmitters. It can be used without configuration from an MCU. However, in connection with MCU, it´s possible to change many parameters including output power, modulation format and a working channel.
  • RFM73-S – 2,4 GHz transceiver, including a high power +20dBm version RFM73P-S2.
  • RFM83C-433S1 – sophisticated 433 MHz ASK/OOK receiver including a version for low voltages RFM83CL-433S operating already from 2.1V
  • RFM85W-433D – 433 MHz ASK transmitter. Excellent features and simple usage. Specially designed for remote control, car-alarms etc. working on 433.92 MHz.
  • RFM12B-868S2P – multichannel 868 MHz FSK transceiver. RFM12B contains integrated functions of a digital data processing like: data filtering, clock recovery, data pattern recognition, integrated FIFO and TX data register. RFM12B enables to provide a clock for microcontroller.

HOPERF – universal RF modules for surprising prices - [Link]

18 Aug 2014

This video describes how a classic double-balanced diode-ring mixer operates. Very basic mixer theory is quickly reviewed, which describes how the sum and difference of the LO (local oscillator) and RF (Radio Frequency) inputs are generated at the IF (intermediate frequency) output. It is also noted that the sum and differences of the harmonics of the LO and RF are also present at the IF output. Math waveforms on the oscilloscope are used to illustrate the operation of the mixer, and the actual waveforms from the mixer are compared to the math waveforms and the differences are discussed. A detailed description of the operation of the mixer is presented, including the switching action of the diodes. Finally, the frequency components are are expected from the mixer are shown on the spectrum analyzer.

How a Diode Ring Mixer works | Mixer operation theory and measurement - [Link]





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