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 Description: Here are two simple Junk Box but extremely useful circuits. They are designed to amplify those flimsy 2.4 GHz Pinhole cameras with such annoyingly low power and short range.
The two transistor version [A] is merely a cascaded version of [B] for greater output. The one transistor version in [B] will easily penetrate two walls of an average household, while the cascaded version [A], will penetrate two floors. Needless to say, a pinhole RF camera’s Antenna connection connects to the Input of either amp. Either amplifier’s ground [Negative] connects to the camera’s Negative, and off course, Positive to Positive. The amps should use the camera’s DC voltage if possible, especially if running the camera off a DC plug pack. All component leads and connections should be short as possible. [point to point connections]. Antenna connects to the RF output.
Note: All inductors are molded chokes. They are critical. Other Higher Gain transistors could be used, but values would have to be altered appropriately.
For those intending to build either project, I strongly recommend you begin with the one transistor version for two reasons. It’s simpler and cheaper, and, when using surface mount components, will easily solder directly on the back of the camera’s circuit board.
When built with care and success, results will be excellent, and will not only encourage you to build the higher power version, but you will have acquired the skill to do so successfully. Most 9 Volt RF Cameras will work quite safely on 12Volts.
Caution: You will be broadcasting Video and probably Audio. The two transistor version is capable of transmitting around ½ Kilometer with the camera’s original antenna, and a great deal further with an extended antenna. It makes Public Listening and Viewing!. As far as I’m aware, the power outputs far exceed the Legal Limits set for such devices in most countries, so, if you live in a built up area, please keep this in mind. Designer & Author: Special thanks to Laszlo Kirschner. |
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 Description: This is a wide band amplifier circuit which is suitable for the frequencies between 10MHz and 500MHz. Wide band RF amplifiers are used in communication receivers, RF measuring equipment and tons of other devices. The circuit described here uses a state of the art transistor to get maximum performance at high frequencies. It can be used as a low noise pre-amplifier due to his low noise characteristics.
Amplifier Specifications:
Supply voltage : +12V
Current : 10mA
Input / output impedance : 50 Ohm
Frequency range : 10MHz – 500MHz
Noise figure : 3.5dB typical
IP2 : 110dBuV
IP3 : 105dBuV This is a classical RF amplifier design. The feedback resistors R3 and R2 define the gain. By changing the values we can get a higher gain at low frequencies, but this will influence the overall gain taper of the amplifier. Coil L2 is used to get more gain at high frequencies. If the value is increased, instability will occur... |
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