Description

Q1 (BC548C) is a modulated oscillator operating in the Commercial VHF Television Band and Q2  (BC548C or 2N4427) is an VHF RF Amplifier.

Tuned circuits consist of C4, L1, C8, L3, and the two 15 pF trimmer capacitors across the collectors and emitters of both transistors. Other NPN transistors like BC54, 2N3642, 43, etc should also work.

The circuit is designed for simplicity, so "No Audio" has been included as this would involve adding at least an RF coupling transformer. The main use for this circuit is for "Security Monitoring".

L1 and L3 can be molded chokes, however, you could use 3-4 turns of insulated copper wire about ¼” diameter. Just spread them until you see a signal.

[VR] is the video balance. It’s adjustment will depend on the type of video input you provide.

If you use a 2N4427 or similar transistor for Q2 (output), you must use a heat sink. The 2N4427 is capable of delivering 1 Watt of RF at VHF frequencies so be sure that either a 50-75 Ohm dummy load or antenna is connected at all times before applying power.
 
Any composite output device will work. Cameras, game consoles, etc.  Tune the transmitter to an unused channel.

Note: You should use an old Analog Tune TV with an indoor antenna.

Designer & Author: Special thanks to Laszlo Kirschner.

Description

This is a high output oscillator set at 1Ghz. Designed out of frustration of not having a matched PNP transistor. The circuit will deliver 3v RF with the components shown.

If you were to use two 100mW rated transistors, you would obtain around 300mW out.

Tuned circuit is L1,L2,C2,C3. Values chosen for 1Ghz for test purposes.

Two 2N4427’s will deliver nearly 3 Watts out at VHF frequencies.

Good Heat Sinking should be used. L1+L2 can be moulded chokes.

Note: Q1+Q2 Must be ‘Well Matched’ to prevent either transistor from doing most of the work.

Designer & Author: Special thanks to Laszlo Kirschner.

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.

The circuit schematic is given in the .rar archive attachment. There are two separate detector units.  Every detector unit consists of a dipole antenna, a choke and a diode. The antenna receives the GSM signals in media. Then a small amount of charge is induced in the choke. The diode demodulates the signal and finishes detecting. The diodes must be schottky diodes or germanium diodes. Since the forward voltage of a silisium diode is high, it won't give a sufficient result in this circuit.

LM358 amplifies the received signal. It contains two separate op-amps that are supplied by a common power source. R3 and R7 resistors determine the gain of the amplifiers. When the resistor values are greater than 10M then the noise level increases. If they are small like about 100k, this time it becomes harder to hear the signal. 

In this article, we point out some important facts in designing RF application PCB boards. Of course there are many other facts that are not listed below but for the beginners these may be enough for now.

First of all, separate the analog , RF and digital parts of your system and try to design the PCB without mixing them. Likewise separate the RF stages like VCO, amplifier and etc. and don't draw one's line through one another's.

λ (Wavelength) = c (The Speed of Light) / f (Frequency)
λ = 300000000/433000000 = 69,28 cm
Max. Line Length : λ/20 = 3,46 cm

In this project we are building a JDM programmer that can handle PIC12, PIC16 and PIC18 family microcontrollers and some popular 24C family EEPROMs. The programmer also provides ICSP feature that allows In-Circuit Serial Programming.  So if you desire, you will not have to carry your MCU each time when you reprogram it. The circuit is connected to the PC via serial port and no external power supply is needed. On the other hand, if you want to use it with a laptop that do not provide RS232 connection, using the circuit with a USB to RS232 converter may not give a proper result.

Supported Devices

EEPROM:  24C01A, 24C02, 24C04, 24C08, 24C16, 24C32, 24C64/65, AT24C128, AT24C256, AT24C512, M24C128, M24C256, 24C515, PCF8572 or 8572 = 24C01, PCF8582 or 8582 = 24C02, PCF8592 or 8592 = 24C04, SDA2506, SDA2516, SDA2526, SDA2546, SDA2586, SDA3506, SDA3516, SDA3526, 4C016 == 24C01, GRS-003 == 24C02, GRN-004 == 24C04, GRN-008 == 24C04, GRX-006 == 24C04, GRX-007 == 24C04, KKZ06F == 24C01, BAW658049 == 24C02, BAW57452 == 24C02, M8571 == 24C02, X24C0

Microchip PIC: 12C508, 12C508A, 12C509, 12C509A, 12CE518, 12CE519,12C671, 12C672, 12CE673, 12CE674,12F629, 12F675, 16C433, 16C61, 16C62A, 16C62B, 16C63, 16C63A, 16C64A, 16C65A, 16C65B, 16C66, 16C67,16C71, 16C72, 16C72A, 16C73A, 16C73B, 16C74A, 16C74B, 16C76, 16C77,16F73, 16F74, 16F76, 16F77,16C84, 16F83, 16F84, 16F84A, 16C505,16C620, 16C620A, 16C621, 16C621A, 16C622, 16C622A, 16CE623, 16CE624, 16CE625, 16F627, 16F628, 16F628A, 16F630, 16F676, 16C710, 16C711, 16C712, 16C715, 16C716, 16C717, 16C745, 16C765, 16C770, 16C771, 16C773, 16C774, 16C781, 16C782, 16F818, 16F819, 16F870, 16F871, 16F872, 16F873, 16F874, 16F876, 16F877, 16F873A, 16F874A, 16F876A, 16F877A, 18F242, 18F248, 18F252, 18F258, 18F442, 18F448, 18F452, 18F458, 18F1320, 18F2330, 18F432

Description

As shown in the schematic, temperature sensor of our electronic thermometer is LM35DZ. There are some kinds of LM35 IC, since it is cheap and easy to find we used LM35DZ in our project. It measures from 0°C to 100°C with a very linear output graph. For one degree change, it increases its output 10mV.On the other hand, this circuit measures temperature values only between +10°C and +39°C.

2 numbered (middle) pin of the sensor is connected to the 5 numbered pins of LM3914 ICs. So every IC determines how many leds of bargraph will bright due to the analog  signal received from the sensor. 2.2 microfarad tantal capacitors are connected between the 2 and 3 numbered pins of LM3914. Resistors in the circuit have %1 tolerance values...