Showing posts with label rf. Show all posts
Showing posts with label rf. Show all posts
Wednesday, November 12, 2014
VHF RF Single Chip Preamplifier circuit with explanation
Here is a high performance RF amplifier for the entire VHF broadcast and PMR band (100-175 MHz) which can be successfully built without any special test equipment. The grounded-gate configuration is inherently stable without any neutralization if appropriate PCB layout techniques are employed. The performance of the amplifier is quite good.
The noise figure is below 2 dB and the gain is over 13 dB. The low noise figure and good gain will help car radios or home stereo receivers pick up the lower-power local or campus radio stations, or distant amateur VHF stations in the 2-metres band. Due to the so-called threshold effect, FM receivers loose signals abruptly so if your favourite station fades in and out as you drive, this amplifier can cause a dramatic improvement.
The MAX2633 is a low-voltage, low-noise amplifier for use from VHF to SHF frequencies. Operating from a single +2.7 V to +5.5V supply, it has a virtually flat gain response to 900 MHz. Its low noise figure and low supply current makes it ideal for RF receive, buffer and transmit applications. The MAX2633 is biased internally and has a user-selectable supply current, which can be adjusted by adding a single external resistor (here, R1). This circuit draws only 3 mA current.
Besides a single bias resistor, the only external components needed for the MAX2630 family of RF amplifiers are input and output blocking capacitors, C1 and C3, and a VCC bypass capacitor, C2. The coupling capacitors must be large enough to contribute negligible reactance in a 50-Ω system at the lowest operating frequency. Use the following equation to calculate their minimum value:
Cc = 53000/ flow [pF]
The noise figure is below 2 dB and the gain is over 13 dB. The low noise figure and good gain will help car radios or home stereo receivers pick up the lower-power local or campus radio stations, or distant amateur VHF stations in the 2-metres band. Due to the so-called threshold effect, FM receivers loose signals abruptly so if your favourite station fades in and out as you drive, this amplifier can cause a dramatic improvement.
The MAX2633 is a low-voltage, low-noise amplifier for use from VHF to SHF frequencies. Operating from a single +2.7 V to +5.5V supply, it has a virtually flat gain response to 900 MHz. Its low noise figure and low supply current makes it ideal for RF receive, buffer and transmit applications. The MAX2633 is biased internally and has a user-selectable supply current, which can be adjusted by adding a single external resistor (here, R1). This circuit draws only 3 mA current.
VHF RF preamplifier circuit diagram
Cc = 53000/ flow [pF]
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Friday, September 12, 2014
Build a Circuit indication for RF Output Transmitters On Air
This is an On Air indicator, ie an indicator schema dr RF transmission, very simple and useful for those who like RF. This schema detects the RF output using a visual indicator, but with some modifications, the LED may be replaced by a relay or any other system that want to trigger when the transmitter is switched on. The output of the transmitter or other RF generator must be connected to this RF input schema.
Simple Circuit indication for RF Output Transmitters
List of components
Resistor R1 560Ω eighth
Capacitor C1 330pF disc
C2 Capacitor 0.1μF disc
Diode D1 1N34 or 1N60
D2 LED
Transistor Q1 2N3904 or equivalent
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