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]
electronics-diy shows you how to easily make a mini FM transmitter:
It transmits FM waves so you could easily receive the signals on your mobile phone, radios, etc. As the name and the picture indicates it is very small and is approximately the size of a 9v battery clip. With this FM transmitter you could start your own mini FM station. The circuit uses BC547 transistor to amplify the signal and then frequency modulate it. It uses “frequency modulation” most commonly known as FM, the same principal to transmit audio signals captured by the microphone.
Mini FM transmitter - [Link]
Stream your music to your entire home !!!
Zola Lab – Portable FM Transmitter
Sparkfun Circular LED
Adafruit Si4713 FM Radio Transmitter
2 x Arduino Pro mini
Sparkfun Rotary Encoder
Catalex 4-Digits 7seg Display
On the top there is a: P2 audio input, a switch on/off, and a female micro-usb for charging Lipo.
DIY portable FM transmitter - [Link]
by ASCAS @ instructables.com:
Have you ever wanted to broadcast your own radio station within the neighborhood? Ever get curious on where people get those “Surveillance Bugs” from spy and action movies? This small and simple FM transmitter is the toy that geeks have always wanted.
FM transmitters can be complicated to build, that’s why I’m teaching you how to make a foolproof FM transmitter. There’s no need to buy kits, this tutorial includes the PCB layout and the schematics. It has a range of up to 1/4 mile or more. It’s great for room monitoring, baby listening and nature research.
The Ultimate FM Transmitter (Long Range Spybug) - [Link]
Ondrej Karas of DoItWireless writes:
This is simple illustration how to build easy PWM LED control with IQRF TR module and a few other components.
This device is powered from 12V/6A DC power supply and can power up to 5m of LED strip. This device can be controlled via RF, buttons or potentiometer. RF controlling is compatible with remote control device RC-04 with low battery signalizing – fast 3 time LED blinking.
RF PWM LED control - [Link]
by brmarcum @ instructables.com:
I got the idea for this circuit from one of my professors at Washington State University. However, the frequencies used in that project would not have allowed for passing higher frequency audio, e.g. 2kHz+. So I built this by modifying the carrier and signal frequencies, using only the Digilent Analog Discovery and the Analog Parts Kit. It should be noted that this circuit is primarily for educational purposes. Also note that there is no radio transmission here either. FM doesn’t necessarily mean radio waves have to involved.
Throughout this Instructable I will be going through some of the functions and features of the Analog Discovery, but it will not be an exhaustive tutorial.
FM Modulation/de-modulation Circuit - [Link]
lamefreaks @ instructables.com writes:
In this instructable I’m going to show you how to build your own portable audio transmitter. This transmits FM waves so you could easily get the signals on your mobile phone, radios, etc. As the name and the picture indicates it is very small and is approximately the size of a 9v battery clip.
Mini Audio Transmitter - [Link]
Bluetooth® Low Energy (BLE) may not be part of your electronic designs just yet, but chances are it will be soon. This wireless connectivity technology has experienced explosive growth over the last three years. It now provides low-power connectivity to millions of electronic devices, such as smart watches, fitness trackers, smartphone accessories, and medical monitors. Thanks to upcoming technical enhancements, BLE is poised to become even more pervasive in the next generation of consumer electronics and the emerging Internet of Things.
Many of the enhancements have been incorporated in Bluetooth 4.1, a recent update to the core specification. Among them are support for more efficient bulk data transfers, greater flexibility in communications between devices, simultaneous dual-mode roles, and the first steps toward IP-based communications. Taken together, these technical improvements make BLE even more attractive from power consumption, performance, and cost standpoints.
In addition to the enhancements outlined in Bluetooth 4.1, the BLE chips themselves have been continuously improving. Thanks to efficiency improvements, transmission power consumption in the second generation of BLE will fall by about 66 percent with no loss of range or performance.
Moving Forward With Bluetooth Low Energy - [Link]
As promised we have built a transceiver USB dongle, for receiving data from various sensors like, smart meters, smoke detectors and temperature/humidity sensors. We’ll provide some code examples on how this trasciever can be used, and software for decoding data from diferent sensors enumerated above.
USB RF 433.92 MHz Transceiver module - [Link]
The filter shape of an HF bandpass filter that is designed for the 30m amateur radio band (10MHz) is measured using a Tektronix MDO3000 mixed domain oscilloscope. The arbitrary function generator (AFG) is used to generate a noise waveform that is flat across the HF spectrum, and the filter shape is then shown on the spectrum analyzer. The filter being measured is the front end bandpass filter of a Softrock Lite II SDR receiver kit.
How to measure an HF Bandpass filter response with the MDO3000 - [Link]