Electronics-Lab.com Blog

Trax writes:

Here is my home-built, cloth iron soldered, range extender for CC1101 (included onboard) RF transceiver chip from Texas Instruments. You could say that it is a CC1101+CC2591, but for 868/920MHz band. I used MAX2233 RF amplifier from Maxim-IC. It can deliver up to +24dBm (250mW) of RF amplification with +10dBm of input.

250 mW RF modem – [Link]

Fred points out this schematic for a rather interesting radiotelephone transmitter instantaneously powered by the operator’s voice. [via]

One of the neatest minimalist amateur radio transmitter circuits around – this one is voice powered – it provides DSB, (double side band)modulation and power from an ordinary 8-ohm speaker – if are in doubt that the circuit works, the maker has the contacts and the voice recordings to prove it!

Voice-powered RF transmitter - [Link]

Dimitris at users.otenet.gr/~meteo writes:

I make simple RF field strength meter to test the remote control from doors ,alarm e.t.c at frequency VHF-UHF, i used one μΑ meter ,2 diodes ,2 ceramic capacitors,a potentiometer,a box ,and one telescopic antenna. When I press the button at remote control,  there is small RF current  and with this meter it can be detected. In that way you can understand if the remote works.

Simple RF field strength meter - [Link] 

It may be used in many receiver configurations: as a simple DC receiver, binaural receiver, phasing receiver, etc. It’s ideal for use with a DSP system. Since the TUF-1 mixer is specified up to 500 MHz, the module will be suitable for 70 cm. By swapping over the RF and IF connections to the mixer (a couple of track cuts and two pieces of wire), LF and VLF reception is feasible.

DC RX Module – [Link]

This website details the design and construction Wave Bubble: a self-tuning, wide-bandwidth portable RF jammer. The device is lightweight and small for easy camoflauging: it is the size of a pack of cigarettes.

An internal lithium-ion battery provides up to 2 hours of jamming (two bands, such as cell) or 4 hours (single band, such as cordless phone, GPS, WiFi, bluetooth, etc). The battery is rechargeable via a mini-USB connector or 4mm DC jack (a common size). Alternately, 3 AAA batteries may also be used.

Output power is .1W (high bands) and .3W (low bands). Effective range is approximately 20′ radius with well-tuned antennas. Less so with the internal antennas or poorly matched antennas. [via]

Wave Bubble: a self-tuning portable RF jammer - [Link]

SquidBee is an Open Hardware and Source wireless sensor device. The goal of SquidBee is getting an “open mote” to create Wireless Sensor Networks (WSN).

How does SquidBee work?

• Acquires values from environment parameters: temperature, humidity, lightness, presence, pressure or (almost!) whatever you can sense
• Operates with these values, when required
• Transmits these values using a low power comsumption wireless technology (ZigBee)
• Sleeps until next timeout and repeats from the first stept

SquidBee: Wireless sensor device – [Link]

Low Power Radio Solutions (LPRS) has claimed that its easy-Radio allows you to ignore the radio link and treat it as if it were a wire. A simple TTL or RS-232 data source is all that’s required to move data from point A to point B, and vice versa, using a pair of easy-Radio transceivers. All of the messy encoding, decoding, and checksum calculations are achieved by the easy-Radio’s internal processor. easy-Radio uses frequency hopping and a maximum of 120 mW of output power to achieve a range of 500-m line-of-sight. My 900-MHz easy- Radios hop at 25 times per second over 25 channels, which, under the control of the internal microcontroller, is transparent to the data radio user.

RF Made Simple - [Link]

josepino.com writes:

This is the basic fm trasmitter that I built. In theory, according to electronics, it shouldn’t work but works fine and is very sensitive. It can transmit the signal up to 45 yards (about 40 meters) . A sensitive FM radio can pick up the signal up to 100 yards (80 meters) but I can’t see any reason for it.

This kind of microphones are also called “spy microphones” but knowing that the battery is bigger than the actual circuit, I can’t see any application like that, anyway, this circuit should be used as educational application only.

Micro FM transmitter - [Link]

Low Power Radio Solutions announces new wireless modules from Circuit Design Inc., the leading producer of narrowband radio modules. The CDP-TX-02E-R and CDP-RX-02E-R radio modules are intended for use in wireless industrial products.

The CDP-TX-02E-R and CDP-RX-02E-R are housed in small, robust shielded cases and require only a small number of additional components to make a working radio system. Thy use narrow-band FSK modulation for high noise immunity, and the high-sensitivity receiver ensures stable operation even in weak signal fields. The modules achieve a line-of-sight communication distance of more than 600 m with only 10 mW power output. They also combine a very small footprint with HF characteristics that guarantee high reliability and resistance to mechanical vibration and shock. [via]

Narrowband radio modules span 600 m with 10 mW - [Link]

This is a mobile phone sniffer circuit that can detect the signals being used in the GSM (Global System for Mobile Communication) band at about 900 MHz. Since the signals are digitally encoded, it can detect only the signal activity, not the speech or the message contents. A headphone is used to hear the detected signals.

Cell Phone Detector - [Link]