A small, simple AM receiver project. This AM receiver can pick up medium wave stations in your area
This circuit can use general purpose transistors, and in this example there are 3 BC109C transistors. In this schematic and BOM there is a 200uH inductor and a trimmer 150-500pF capacitor, though these parts can be salvaged from an old AM radio, to preserve the directional nature of a tuning coil, and an adjustment knob (plate capacitor) that work well for radio reception.
The 120k resistor is for regenerative feedback between the Q2 NPN transistor and the input to the tank circuit. The value of this resistor is important to the performance of the entire circuit. In fact, it may be better to replace the fixed value with a variable resistor paired with a fixed resistor to adjust the oscillation and sensitivity of the circuit. All the connections in this circuit should be short to minimize interference.
Performance of the circuit will vary depending on stray capacitance in your layout, the inductor winding/core/length, etc. Changing values of some of the capacitors, or adding them, as well as a potentiometer in the feedback loop can help with the performance of the receiver. With such a small circuit that is affected so much by its construction and its environment, a lot of hand tuning and experimentation will be fun, instructive, and possibly necessary to make it work best.
Simple AM Receiver Project - [Link]
This is a VCO FM Transmitter with range 500m – 4km depending on antenna used
- Power supply: 12-14 V stab., 100 mA
- RF power: 400 mW
- Impedance: 50-75 ohm
- Frequency range: 87,5-108 MHz
- Modulation: wideband FM
FM VCO Transmitter - [Link]
By Bill Schweber:
In a wireless design, two components are the critical interfaces between the antenna and the electronic circuits, the low-noise amplifier (LNA) and the power amplifier (PA). However, that is where their commonality ends. Although both have very simple functional block diagrams and roles in principle, they have very different challenges, priorities, and performance parameters.
How so? The LNA functions in a world of unknowns. As the “front end” of the receiver channel, it must capture and amplify a very-low-power, low-voltage signal plus associated random noise which the antenna presents to it, within the bandwidth of interest. In signal theory, this is called the unknown signal/unknown noise challenge, the most difficult of all signal-processing challenges.
Understanding the Basics of Low-Noise and Power Amplifiers in Wireless Designs - [Link]
This is a small circuit with two maxim’s ic, MAX4467 as microphone amplifier and MAX406 as VCO FM transmitter. It’s suitable for short range FM transmittion aka wireless FM microphone.
Here is a very simple, inexpensive and interesting project which provides lot of fun to a home experimenter or hobbyist. This simple transmitter can transmit speech over a short range. It can be used as a simple cordless microphone. The circuit uses two integrated circuits from Maxim. IC1 a MAX4467, is an amplifier raising the microphone signal to a level suitable for frequency modulation (FM). IC2 is a voltage-controlled oscillator (VCO) with integrated varactor (a.k.a. varicap diode).
FM Transmitter MAX4467 & MAX2606 - [Link]
SL030 module communicates through favorite I2C interface and supports a wide scale of secure RFID technologies on the frequency of 13.56 MHz.
RFID modules Stronglink provide an excellent quality for an unbeatable price, that´s why from now you can find in our store another member of readers/ writers SL0xx module SL030. In many ways is the SL030 similar to other readers of the SL0xx family (especially SL031), which were introduced to you in the article „Stronglink modules will provide you a highly secure RFID”.
SL 030 supports the most of known RFID protocols on the frequency of 13.56 MHz like MIFARE 1k, MIFARE 4k, MIFARE Ultralight as well as NFC NTAG203. Built-in antenna and automatic detection of tags significantly simplify usage of the module. Also positive is the fact, that despite a 3V power supply, the outputs are 5V tolerant, thus combination with a 5V logic should be trouble free. SL030 contain besides an I2C communication interface also a direct output (OUT pin) indicating presence of RFID tag in a reach. SL030 can be set up to 4 different I2C addresses (1010000-1010011) by means jumpers JP1 and JP2. The communication itself runs in a standard form usual for an I2C bus. Commands (from a Host microcontroller of your application) are sent in a form of „Start+Address+Data_Length+Command+Data+Stop“. Overview of available commands is displayed in a Table no. 3. Result of operation is sent back from SL030 through I2C in a form of Command+Status+Data. Byte „Status“ indicates result of operation (Success/Fail,…) – table no. 4. Overview of possible statuses is summarized in section 4-3.
Detailed information will provide you the SL030 datasheet and examples of source codes ARM, AVR, MCS51, MSP430 a PIC.
Upon request we´re able to provide you any other Stronglink type within few days. In case of interest please contact us at firstname.lastname@example.org.
SL030 recognizes Mifare and NFC too – [Link]
By Bill Schweber
The explosive growth of “wireless” systems has led to a simultaneous expansion in the use of RF connectors and their associated cables. These assemblies are increasingly vital links between multiple circuit boards, between antennas and front ends, and between power amplifiers (PAs) and antennas. They are instrumental to the operation of such wireless devices and systems as cellular telephones, wireless data networks and advanced radar and electronic-warfare (EW) systems.
Connectors for RF systems have the simple yet critical task of transferring signals from one location to another, with little or no change to the signal (although in reality even with high quality RF cable between the antenna connector and the antenna engineers often factor in a 0.2 dB loss per coaxial connector in addition to the cable attenuation itself).
Selecting an RF Connector for your Wireless System - [Link]
Travis Goodspeed has been experimenting with remote satellite tracking over the internet. His setup uses a satellite dish originally used with a mobile earth station on maritime vessels. Movement of the dish is accomplished with servos and an EiBotBoard wired into a BeagleBone. Travis writes:
My initial build using an RTL-SDR dongle. Data processing is done on my server, with the BeagleBone forwarding data from rtl_tcp. To avoid offending the FCC and ham radio operators everywhere, I disabled the dish’s 1.5GHz transmitter and use only the 1.6GHz downlink antenna. If I can justify the extra weight, I’d like to drop the RTL-SDR in favor of a USRP2 over Gigabit Ethernet in order to get greater bandwidth and sensitivity.
Tracking low earth satellites using RTL-SDR - [Link]
Making an FM using TEA5767 module:
I’ve started to build a little FM radio with one of this cheap modules with a Phillip chip, the TEA5767. I will control it with a MSP430, probably I’ll use some kind of encoder to change stations and a potentiometer for the volume.
The TEA5767 is a single-chip electronically tuned FM stereo radio for low-voltage applications with fully integrated Intermediate Frequency (IF) selectivity and demodulation. Most of the information of this devices is from the datasheet and this app note.
Making an FM radio-Part 1; the TEA5767 - [Link]
machinegeek @ dangerousprototypes.com writes:
panStamps are small open source wireless modules designed to add RF connectivity to sensors, MCUs and similar projects. The crew at panStamp is in the process of developing a new module based on the TI CC430F5137 SOC. Programming will be via the Arduino IDE, facilitated through a port being developed by the open source Energia project.Commercial release of this new line of panStamps is planned for September-October. For more info visit PanStamp.
panStamp developing MSP430 based module - [Link]
Semtech has launched the SX1272, the first product in a new family of long-range Radio Frequency Integrated Circuits (RFICs) with a transmission range up to 15 kilometers. The SX1272 integrates Semtech’s new LoRa (long range) modulation technology to enable drastic range improvements over alternative modulation methods. Compared to a typical range of 1 to 2 kilometers with smart meter transceivers using FSK modulation, the new device can transmit over more than 15 km, operating under the same conditions and regulatory limits.
The new RFIC achieves receiver sensitivity up to -137 dBm using a low-cost crystal, compared to current state-of-the-art FSK devices with a sensitivity of -115 dBm with a comparable crystal or -125 dBm using an expensive temperature controlled crystal oscillator (TCXO). The in-band interference signal rejection is also 25 dB better than FSK devices. This makes the device especially effective in ISM band applications because it provides immunity from sub-GHz 4G/LTE signals. [via]
Smart Meter Transceiver IC has Range of 15 km - [Link]