This Lowpass filter used for the amplifier can also be constructed as a standalone filter for use with any other 2 Meter Amplifier upto 200 Watts output.It was designed to bring the Harmonic & Spurious outputs generated by the amplifier module to acceptable levels ( Note within specification of the UK Amateur Radio transmitting licence harmonic spurious levels are not specified to absolute levels, these were taken from the limits specified for the adjacent commercial bands) Initial [...]
This RF filter circuit is a bandpass filter VHF FM for frequency 88-110 MHz.The schematic you find here comes from an old Dutch magazine called Free Radio Magazine and is designed by VEROBB-DX. The filter is build symmetrical and has both INPUT and OUPUT impedance of 50 Ohm. So it can be used after each buffer-, driver- or amplifier-stage. The dimensions of the coils' diameter is the INNER-diameter of the coils!!! Make sure that the coil's end-wire is in a axial line with the coil and [...]
The FM transmitter circuit is a high quallity transmitter that includes RDS/SCA input and Audio/MPX input with optional preemphasis. It can be used with or without stereo encoder. Tuning over the FM band is provided by two buttons. The transmitter can work also without the LCD display. This FM transmitter is easy to build, and a high-quality PLL FM transmitter with typical output power of 5W and designed with no-tune method (broadband method). PCB You may choose between sin [...]
This RF amplifier for FM 88-108 MHz with no tune (broadband) needed to cover all the FM Band. This RF Power amplifier is equiped with two Philips bipolar transistors : the BLV10 & BLW87. All the impedance networks (Input-Output) of this RF amplifier have been determined by using the softwares: Mimp.EXE. This RF Amplifier need a 9 elements low pass filter ensures that its harmonic frequency meet at least a 60 dB rejection from the carrier.(RF Simulation with RFSIM99) This RF FM ampl [...]
This RF amplifier for FM 88-108 MHz with no tune (broadband) needed to cover all the FM Band. You need the 2N3866 driver stage to boost properly the BLV10 transitor. All the impedance networks (Input-Output) of this RF amplifier have been determined by using the softwares: Mimp.EXE - Genesys. RF FM Power Amplifier Schematic-PCB Due to the good harmonic rejection of the RF amplifier design, a low pass filter is not necessary. Or you can download RF Filter Design AADE and RF Filter Desig [...]
Here's RF Power Amplifier for QRP with low cost. This circuit is a broadband one from 1.8 to 30 MHz, so it is "no-tune" and you need only to regulate the quiescent current bias multiturn trimmer of each Mosfets couple. This means also low efficiency (for a lower IMD it is even low as around 20-30%) together with good heat sink + blower system. HF QRP Linear Amplifier with 2x 2SC2166 + 2x 2SC1969 Push Pull Transistors (13.8V) The push-pull configuration permits to get a better att [...]
This is a very straightforward field-strength meter circuit. The first stage acts as a crystal receiver. Use a germanium detector diode (like 1N34, but AA119 is much more common in Europe), a silicon one won't do. The frequency is determined by L and C. For the FM band and VHF, wind a coil 5mm in diameter, 6-8 turns of coated wire 1mm thick. You can always vary the frequency by spacing the turns a bit looser or tighter. C is much less critical. Something around 100p is preferable, thou [...]
In the amateur radio communications, this Yagi antenna is usually used for long-distance communications, ham are usually first GP without the use of directional antenna contact with each other, and then YAGI antenna at the other location, and then start communication. In other words, this antenna to match the one antenna rotator to achieve its effectiveness, because the antenna if there is no firing at each other, the effect would not gain GP antenna so poor in the use of such antennas [...]
This is an unique project is one of the most trusted homemade test instruments to have, once you get your FM transmitter up and running. This simple little device (the Switchable RF Probe-Watt Meter), is capable of finding your FM transmitters : Unloaded RMS Output Voltage Loaded RMS Output Voltage Output Impedance Output Wattage Construction of the Switchable RF Probe/Watt Meter Print out the PCB template to the left. From the left to the right of the PCB template. Begin [...]
This RF amplifier circuit is suitable for the frequencies between 10MHz and 500MHz. These kind of amplifiers are called wide band amplifiers. Wideband amplifiers are used in communication receivers, RF measuring equipment and tons of other devices. The RF power amplifier 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. This is a classical RF amplifi [...]
This is a RF Linear amplifier for QRO using power mosfet IRF840 with power out 60 Watts. It's simple all solid state circuit. The IRF series of power transistors are available in various voltage and power ratings. A single IRF840 can handle maximum power output of 125 watts. Since these transistors are used in inverters and smps they are easily available for around Rs: 20/-. The IRF840 linear amplifier can be connected to the out put of popular VWN-QRP to get an output of 60 Watts. The [...]
This circuit is an RF probe that is used to directly measure the level of RF voltage present at a particular point and is one of the most useful test instrument in the hands of the home brewer. This RF Probe is normally used with a digital multi meter to indicate the voltage level as dc voltage which is equivalent to the RMS value of the RF voltage being measured. However, the level of RF voltage being measured provides useful information only when the probe has been designed for use w [...]
The dummy load circuit described here is capable of handling up to 10 watts of RF power for a couple of minutes, and is designed for the widely used 50 ohms impedance. It consists of ten parallel connected 560 ohms 1 watt resistors, R1 through R10, a voltage divider, R11-R12, and a rectifier D1-C1. Apart from loading the transmitter output with a minimum of reflected power, the dummy load also provides a direct voltage output to which a voltmeter may be connected to measure the RF powe [...]
This RF circuit is Power Meter. It's a simple set up which will enable them to measure the out put power of their transmitter. All that they require is a good multimeter which has a sensitivety of 20k ohms/4 Watts which is adequate for low power transmitters. The 8k resistor should be kept close to the out put terminal of the transmitter. Switch on the transmitter in the CW mode and measure the DC voltage with the multimeter. If the voltage is V then the out put power is given by [...]
This RF transmitter circuit is FM wireless microphone that transmit voice signals to any FM Radio receiver 100 meters away. The circuit is basically a frequency modulated transmitter working at 100 MHz. The frequency of the transmitter can be varied slightly by changing the trimmer C5. You can use ordinary condenser mike in this circuit. The transistors can be replaced by any low power transistors like BC148 or BF494. The coil L1 is air core 6 turn 24 SWG. Third turn is tapped and conn [...]
This transmitter circuit is a miniature medium wave (MW) transmitter. It's a very simple, inexpensive and interesting project which provides lot of fun to a home experimenter or hobbyist. This simple transmitter can transmit speeches or songs within a short range. The MW transmitter circuit uses only one transistor. The entire circuit can be easily assembled on a prototyping printed circuit board. After assembling all the components properly put the whole assembly in a plastic enclosur [...]
This Infrared (IR) transmitter can be used in many projects. This IR transmitter sends 40 kHz (frequency can be adjusted using R2) carrier under computer control (computer can turn the IR transmission on and off). IR carriers at around 40 kHz carrier frequency are widely used in TV remote controlling and ICs for receiving these signals are quite easily available. The circuit can be controlled using any TTL or RS-232C level control signal which makes the interfacing very simple. The cir [...]
This RF circuit is RF Switch will work from almost any RF-frequency an from 0.1W up to 100W. It can be used to switch on/off pre-amps or amplifiers, repeater rf-in sensor, or anything else you want to switch on or off when starting to transmit. The RF Switch schematic will work just fine between 50 MHz and 440 MHz . It can be improved (peaked) if you should use it for one band only, say for example the 2 meter band or for a high or very low used TX power outputs. To use the RF switch f [...]
The amplifier is for 144 MHz and build into a metalbox measuring 240x160x160 mm. The space is mainly taken up by the 28 V / 7 A power supply. On the rear side of the box the amplifier is mounted against a big heat sink. The amplifier itself is build on a piece of double sided PCB about 140x100 mm. There is no PCB artwork for the amplifier, simply cut out square islands with a knife, for soldering the transistor basis and collector and the terminals of the tuning capacitors. This is a f [...]
This simple seven element Yagi antenna is ideal for portable operation. The elements can be removed and replaced in a couple minutes. The 2.42 Metre boom will fit inside my car. All of the elements are made from 6mm solid aluminium rod. The boom is made from 50x25mm (2x1 in) timber. The driven element of the antenna is a half wavelength dipole. Unlike the more common type of folded dipole, this dipole is folded on one side but not on the other. For want of a better name, lets call it a [...]