RF Transmitter Circuits Resources

RF Amplifier Broadband 88-108 MHz 20W

noreply@blogger.com (Quick Zone) — Sat, 19 Sep 2009 04:56:00 +0000

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 amplifier has a 21 dB gain with a 55 to 65% efficiency.

RF Power Amplifier PCB Layout

Source: 20W FM AMPLIFIER

RF Amplifier Broadband 88-108 MHz 8W

noreply@blogger.com (Quick Zone) — Sat, 19 Sep 2009 04:28:00 +0000

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 Design Software-SVCFilter.

This RF amplifier has a 22 dB gain (with driver stage) and provides 8W with a 55% efficiency.

Source: 8W FM AMPLIFIER

Broadband RF Power Amplifier 1.8-30 MHz

noreply@blogger.com (Quick Zone) — Mon, 02 Feb 2009 11:24:00 +0000

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 attenuation of even harmonic frequencies (a good benefit since the second is the closer 2x fundamental freq.). The output stages have 2 separate transformers in each couples so the power supply current does not flow in to the output transformer to avoid saturation and the floating winding helps for balance for harmonic attenuation and stability.

HF QRP Linear Amplifier with 2x IRF510 + 2x IRF510 Push Pull Low Cost Mosfets (28V)

We have emploied also in this low power unit the circuit found in higher power units to stabilise thermically and regulate the bias current around a trusted LM723 IC, the transistors are used only for PTT control. In the first stage Mosfet couple we have used a feedback circuit to optimize gain-frequency response. Without it the low frequency gain is very high, too high: at 3 MHz 50 dB ! and a lower 30 dB at 30 MHz, but with this feedback circuit the overall gain variation is close to a +/-3 dB, a good result.

We tried a similar feedback in the output couple but results where a poorer IMD performance so it has been omitted. We selected Mosfets couples in a simplified way (while not so precise RF matching practice) measuring drain-source resistence: a better way could be to measure in a simple test circuit current drain at a given gate voltage applied for all devices and choose the ones that showed closer current values.

Broadband RF Power Amplifier 1.8-30 MHz in detail

Field-Strength Meter

noreply@blogger.com (Quick Zone) — Fri, 21 Nov 2008 05:57:00 +0000

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, though.

The second stage of circuit is based around the versatile 2N3819 JFET high-impedance amplifier. With the 470k potentiometer you can adjust sensitivity of the circuit. The trimmer is used to zero the meter. Use any old 50mA or slightly smaller ammeter from the junk box.

Problems:
You can't expect great performance from such a simple detector-based meter. Sensitivity is just adequate enough to get a basic idea of the power that your transmitter is capable of.

Possible uses:
Use the field-strength meter to find out when a transmitter is operating at optimal power. It can be very handy when aligning stages (like in case of the 4W transmitter) or experimenting with different antennas. Link

9 Elements Yagi Antenna 144 MHz

noreply@blogger.com (Quick Zone) — Wed, 12 Nov 2008 18:43:00 +0000

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 must be With a rotating antenna motor will achieve the best results!

Installation:
This Yagi Antenna is to use aluminum antennas, and materials in line to buy aluminum, the production can not run if the material can be used to damage the TV antenna modifications.

First main bar size clearly marked and then saw the CD and drilling holes. Drilled holes in the lines very carefully, the center hole with the main vertical rod, depending on the construction plans after the completion of the most important Adjustment is a correction. Adjustment, the antenna away from the high degree of the best in more than two meters, and metals and away from buildings, first notch in order to form cross-linked with the antenna, fine-tuning capacitor in about 20 pF position adjustment so that short-circuit bar UHF antenna resonance in two paragraphs, and then get connected to the settlement table-wave cable, VSWR table, and the transmitter, an adjustment to short-circuit and capacitive rod position to obtain the lowest SWR. This antenna with a length of about two meters Please be careful to avoid the installation of high-tension line in the next to the construction. This Yagi antenna gain of about 15dB.

9 Elements Yagi antenna 144 MHz in detail

Switchable RF Probe-Watt Meter

noreply@blogger.com (Quick Zone) — Sat, 08 Nov 2008 03:37:00 +0000

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 by hooking up your transmitter, RF Probe/Watt Meter and DVM/Analog Meter.
Make your tests with your homemade device

Once your FM transmitter, RF Probe/Watt Meter and DVM/Analoyg Meter is set up, now comes the time to make your tests with your homemade device. Remember now, there are 4 items that we will investigate..

Finding the transmitters' unloaded RMS output voltage.
Finding the transmitters' loaded RMS output voltage.
Finding the transmitters' output impedance.
Finding the transmitters' output wattage.

A step-by-step procedure will be used in order to find these 4 items.

Switchable RF Probe-Watt Meter in detail by Patrick

10-500 MHz Wideband RF Amplifier

noreply@blogger.com (Quick Zone) — Tue, 28 Oct 2008 06:46:00 +0000

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 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.

Dimensions of L2 are:
6 windings, inner diameter is 3mm and wire thickness must be 0.4mm. In the proto type I used and SMD type for L1, make sure it’s a high Q coil. The transistor, which is used here, is a wide band transistor with an Ft of 9 GHz. Like in all other RF circuits make sure that the connections are short as possible.

Source : http://www.antrak.org.tr/gazete/082003/yilmaz_dosyalar/WB_amp.pdf

60W Linear Amplifier with IRF840

noreply@blogger.com (Quick Zone) — Sun, 12 Oct 2008 21:56:00 +0000

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 circuit draws 700 ma at 60 Volt Vcc. Good heat sink is a must for the power transistor.

Alignment of the Linear Amplifier
Connect a dummy load to the out put of the circuit. You can use some small bulb like 24V 6 Watts as the dummy load. I have even used 230V 60 Watts bulb as dummy load with my IRF840 power amplifier working at 120Volts. Adjust the 10K preset to get around 100 ma Drain current. I used gate voltage of 0.8V with my linear amplifier. A heigh gate voltage can make the power transistor get destroyed by self oscillation. So gate voltage must be below 2V and fixing at 1V will be safe.

Bifilar transformer T1 is wound with 8 turns 26SWG on 1.4 x 1 balun core. The coil on the drain of IRF is 3 turns 20 SWG wound on 4 number of T13.9 torroids (two torroids are stacked to form a balun core). The RFC at the Vcc line is 20 Turns 20 SWG wound on T20 torroid.

Source: http://www.flashwebhost.com/circuit/60_watts_rf_amplifier.php

Designing RF Probes

noreply@blogger.com (Quick Zone) — Sun, 12 Oct 2008 21:47:00 +0000

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 with a specific multi meter. The design of the RF probe is a function of the DC input resistance of the meter we intend to use with it. If a new meter with a different input resistance is used with the probe the reading will be inaccurate.

Below shows the construction of the RF probe. The rectified DC voltage at the cathode of the diode is at about the peak level of the RF voltage at the tip. The value of the resistor R1 is so chosen that when this resistor is connected in parallel with the input resistance of the digital multi meter, the peak value is about 1.414 times the RMS voltage. R1 has to drop this excess voltage so the meter indication is accurate. If we know the input resistance of the meter, we can calculate the value of R1 as follows. Usually, digital multi meters have an input resistance of 11 meg ohms. In this example we shall take the input resistance of the meter as 10 meg ohms which will make calculation easier to understand.

10,000,000 X 1.414 = 14,140,000
R1 = 14,140,000 - 10,000,000 = 4,140,000 Ohms = 4.14 Meg Ohms
4.7 meg ohms is the value chosen in all circuits since digital multimeters have input resistance of 11 meg ohms.
Circuit By RAMASWAMI VU2PRI.

Source: http://www.flashwebhost.com/circuit/rfprobe.php

RF Dummy Load

noreply@blogger.com (Quick Zone) — Sun, 12 Oct 2008 21:34:00 +0000

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 power.

If the dummy load is used for power levels higher than 10 watts simply use more, or higher wattage resistors to give a total of about 50 ohms. For instance, by using twenty 2 watt 1,200 ohms resistors instead of R1-R10 and 150 ohms resistors for R11 and R12, the dummy load is turned into a 40 watt version. The diode may be almost any Schottky type. Types like BAT85 and HSCH1001, for instance, are also suitable. Even a germanium type like the AA119 will work, but then for low powers only.

The dummy load is housed in a tin can of which the cover is used to mount the components. As illustrated, the ten 560 ohms resistors are soldered in a circlearound the center pin of the BNC socket. Their ground terminals are soldered flush to the inside of the cover. Capacitor C1 is a feed through type for which a small hole must be drilled in the cover. All resistors should be mounted with the shortest possible lead lengths to keep the reactive component of the dummy load as small as possible. After mounting the parts, the cover is fitted on to the tin can again, and soldered all around to seal the dummy load completely. Do not drill ventilation holes in the tin can because that will defeat the purpose of making a non-radiating load. The can may get quite hot when transmitter power is applied for a while, but that is no cause for concern.

The voltmeter read-out produced by the dummy load may be calibrated against a professional RF voltmeter (for instance a 'real' Bird Thruline). The voltages obtained at different RF power levels are noted so that a graph can be made. Depending on the reactive characteristics of the resistors used, the dummy load should exhibit a VSWR of less than 1.5 for frequencies up to 450 MHz. Resistors R13 may be omitted if the dummy load is always used with same voltmeter.

Source: http://www.flashwebhost.com/circuit/rf_dummy_load.php

Simple RF Power Meter

noreply@blogger.com (Quick Zone) — Sun, 12 Oct 2008 21:28:00 +0000

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 Power = V2/50

The RF Power Meter circuit can handle up to 5 Watts. Above this the diode may go QRT. All components should be mounted as close as possible.

Source: http://www.flashwebhost.com/circuit/pwrmeter.php

FM Wireless Microphone

noreply@blogger.com (Quick Zone) — Sun, 12 Oct 2008 18:06:00 +0000

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 connected to telescopic antenna. You can replace telescopic antenna with a small piece of wire.

Source: http://www.flashwebhost.com/circuit/fm_wireless_mike.php

Miniature MW Transmitter

noreply@blogger.com (Quick Zone) — Sun, 12 Oct 2008 17:58:00 +0000

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 enclosure provided with a telescopic antenna. Now keep your MW radio and the transmitter on a table about one meter away from each other. Switch on the radio receiver and turn to a clear spot where no broadcasting station is present. Now switch on the transmitter and turn the gang condenser. At some position loud hissing sound will be heard from your receiver. Stop the gang condenser at this position. Speak some thing to the speaker which serves as the microphone. Now turn the radio receiver to get clear and loud sound.

The transmitter have a range of 200 meters. You can increase the range by using an external antenna and sensitive receiver at receiving end.

Souce: http://www.flashwebhost.com/circuit/miniature_mw_transmitter.php

Simple Infrared Transmitter Circuit

noreply@blogger.com (Quick Zone) — Sun, 12 Oct 2008 17:46:00 +0000

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 circuit can be used for example for using computer to generate IR remote control signals or experimental IR data transmission.

The circuit works so that when the input (LEFT/RIGHT CONTROL) pin is in logic high state (+4..15V) the transmitter is on and when it is in logic low state (+1V..-15V) the transmitter is off.

Infrared transmitter parts list

C1 1 nF
C2 10 nF
C3 220 nF
D1,D2 1N4148
D3 TIL31B (or other suitable IR LED)
R1 1 kohm
R2 22 kohm trimmer
R3 120 ohm
U1 NE555, LM555 or similar

IR receiver and sega glass interface circuit

I designed the circuit to make my Sega 3D glasses wireless, but system did not work as well as I wanted it to work. I used the circuit below to receiving the IR signals and controlling the IR glasses.

Component list

Amount Component
2 10 kohm resistor
2 22 kohm resistor
1 10 uF electrolytic capacitor
1 100 nF capacitor
1 10 nF capacitor
1 78L05 regulator (normal 7805 works also)
1 GP1U52X receiver module
3 1N4148 diode
1 2N2222 transistor (BC547 works also)
1 3.5 mm stereo jack

Source: http://www.tkk.fi/Misc/Electronics/circuits/ir_send.html

RF/VHF Switch with One Transistor (RF-Sensing)

noreply@blogger.com (Quick Zone) — Mon, 29 Sep 2008 12:17:00 +0000

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 for frequencies below 50 MHz then you should use a higher value capacitor. For HF use a capacitor of 27-47pF. If you the RF switch at high RF power you should increase the value of 220 Ohm resistor. Try a 1 ... 22K resistor.

Souce: http://users.belgacom.net/hamradio/homebrew.htm

100W Transistor Amplifier for 144 MHz with MRF317

noreply@blogger.com (Quick Zone) — Mon, 29 Sep 2008 11:44:00 +0000

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 fast and efficient way of building and it leaves an almost unbroken ground plane for the high RF return currents. The rest of the components are placed free standing above the board, as can be seen on the pictures.

This RF transistor amplifier is simplicity itself, as the diagram will show. Input and output circuits are calculated based on informations from the MRF317 datasheet, however as the data are for class C operation, and the amplifier is biased in class AB, the input circuit had to be optimised by experiments. It's important that C3 is placed close to the transistor and can handle the high RF currents at this point.

Input Circuit

Output Circuit

The resulat of the amplifier test, with 10 W drive and abt. 26 V supply voltage I have 90 W output. The transistor is designed for 28 V and will give more than 100 W, but I had to settle for a little less. The reason is, that my transformer/capacitors was a bit underrated and could not deliver max. current without ripple "break through". So by reducing the output voltage, the regulator had a little more headroom to work with.

Source : http://hjem.get2net.dk/ole_nykjaer/oz2oe/mrf317/317.html

Portabel Yagi Antenna for 144 MHz

noreply@blogger.com (Quick Zone) — Mon, 29 Sep 2008 11:31:00 +0000

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 'half folded dipole'. The co-ax cable braid is connected to the centre of the dipole. The co-ax centre conductor is connected to the folded dipole section (see diagram above).

The boom length for Yagi antenna has to be around 2.4 metres. A shorter boom would give less gain, a longer boom would not fit in my little Honda motor car.

Source: http://homepage.eircom.net/~Eei9gq/yagi.html

Approximate Air Coil Inductance Calculator

noreply@blogger.com (Quick Zone) — Fri, 26 Sep 2008 19:11:00 +0000

Here's a tool for calculate air inductance and it's valid only for one layer, tightly wound, air core coils without gaps between the turns.

Approximate Air Coil Inductance Calculator

Design an L-C Low Pass or High Pass Filter

noreply@blogger.com (Quick Zone) — Fri, 26 Sep 2008 18:52:00 +0000

Here's a tool for design L-C Low pass or High pass filter. This web based application allows the user to design simple radio frequency filters with inductors and capacitors. These filters are most effective between 50 KHz and 500 MHz. Below 50 KHz active filters are usually more cost effective and above 500 MHz strip lines are generally used.

Below the link and you just select and type commands in a box, you can find the value of L-C:

CALCULATE L-C FILTERS

Optimized 6/9 Element VHF Yagi Antenna

noreply@blogger.com (Quick Zone) — Wed, 24 Sep 2008 08:14:00 +0000

This antenna project written by Guy, ON6MU. The reflector and driven are copper. 1/4 inch copper pipe used shorting bar for gamma. Held in place using stranded copper wired. Permantly soldered in place after final tuning adjustments. 14 gauge wire with shrink tubing installed at SO 239 or N connectror. "Coax seal" on tip of gamma rod to keep out moisture, printed grey.

Source: http://users.belgacom.net/hamradio/schemas/yagi_vhf_antenna.htm

80W RF Power Amplifier Up to 30 MHZ

noreply@blogger.com (Quick Zone) — Tue, 23 Sep 2008 11:20:00 +0000

Here's RF power amplifier project, especially those who make QRP transmitters or exciters, are always looking for a linear amplifier to get more RF Output. Schematic and PCB are based on an article in ARRL Handbook 1981-3 detailing MRF454 Linear amplifier construction by K7ES.

In PCB, the power amplifier has made is using a DIP 723 in place of G package which was not available to me at that time and include a PTT control by way of a PNP switch. Please refer to original article for more details on this project.

Source: http://datasheets.foxdelta.com/hflinear.html

20W UHF RF Amplifier for 430-470 MHz

noreply@blogger.com (Quick Zone) — Tue, 16 Sep 2008 16:04:00 +0000

This UHF RF Amplifier circuit uses MH720A1 hybrid power module from Mitsubishi that operates between 430MHz and 470MHz and will output approximately 20 Watts of RF power from a 10mW input source. This amplifier can be used as part of a 457MHz pager transmitter.

This hybrid power modules amplifier are offered by various manufacturers and can often be obtained second hand of amateur rallies. Most hybrid modules require an input power of 20dBm. Therefore, a driver stage before the hybrid module input is incorporated.

The Power Amplifier module suppresses output harmonics through an internal filter. As almost all components are SMD, the use of hollow rivets is unavoidable if the ground plane on one side and the ground tracks on the other side of the PC board is not interconnected. The O/P coil consists of 9 windings of 1mm silver plated copper wire, wound 7mm in diameter.

Source: http://www.ajpotts.fsnet.co.uk/uhfrfamp.html

FM Stereo Encoder with Overshoot Compensator

noreply@blogger.com (Quick Zone) — Sun, 07 Sep 2008 05:41:00 +0000

The following circuit is stereo encoder for fm broadcasting transmitter. The stereo encoder circuit schematic divided by into five parts.

Digital Section (click for schematic)
Analogue Section (click for schematic)
Input Output and PSU (click for schematic)
Overshoot Compensator (click for schematic)
23 KHz Oscillator and Logic (click for schematic)

The stereo encoder circuit uses oversampling method and keep 23 KHz spectrum frequency clean clean .

6W RF Power Amplifier with 2SC1971

noreply@blogger.com (Quick Zone) — Sat, 06 Sep 2008 16:42:00 +0000

This RF Power Amplifier taken from FRB Amplifier Kit. It uses 2SC1971 for FM broadband design from 88 to 108 MHz.

Power Amplifier Schematic Circuit

Power Amplifier Printed Circuit Board and Component Layout

Assemble Instructions

RF power amplifier assemble by soldering the components to the pads indicated. Keep coil, resistor, and capacitor leads as short as possible. The coils should be 3/16" to 1/4" above the board and separate turns by one wire diameter. Bend leads to form a little mounting foot for soldering to the circuit board.

Tuning and power output are affected by the distance between the coil turns, you can make fine adjustments by either spreading or compressing the coil slightly. The area surrounding the pads is ground. C2, C3, C4, C6, C7, C8, C9, C10, L2, and R1 are soldered at one end to ground as well as the shield braid on the coax cables. Bolt Q1 to a small heat sink or the chassis with heat sink thermal compound or gray thermal pad underneath the tab. With an input level of 200-500mw, you should see an output of 5-6 watts. Be sure to have a proper dummy load (50 ohms) or tuned antenna connected to the output, doing otherwise will likely destroy the transistor.

1000W FM Amplifier Service Manual

noreply@blogger.com (Quick Zone) — Sat, 06 Sep 2008 13:48:00 +0000

Here's 1000W FM amplifier and it a modern FM amplifier which integrates solid state reliability with the digital technology which makes it safe and easy to use.

High gain MOSFETs transistors and systematic use of state of the art manufacturing methods. The amplifier, of simple and rugged construction, is able to satisfy the requests of all those end-users looking for top-quality equipment at reasonable prices

You can use this fm amplifier service manual for reference building power divider, power combiner, lowpass filter, and etc.

The power amplifier is lightweight with broad-band characteristics over the entire VHF FM range. The compact design and the internal configuration of the modules, allow excellent access to all components. All the power components are generously over-rated to ensure excellent reliability. The cooling system of the equipment makes possible to keep all components which dissipate heat, at low temperature figures, thus permitting reliability and very high MTBF.

1 KW Power Amplifier Module The input power of the module is connected to a Wilkinson splitter, and is then sent to the input of two 3dB couplers. In case of failure of one of the MOSFETs, the unbalanced power is connected to four resistors. The amplifier circuit is composed of four BLF278 MOSFETs which permit a very high redundancy thanks to four- level modularity. The MOSFETs are provided with a bias circuit that assures the optimal impedance matching. The temperature, the Voltage and the RF Power figures are controlled by the microprocessor board.

Download Service and Operating Manual

Filter And Directional Coupler This module is composed of the Low Pass Filter and of the Directional Coupler.The filter is constant matching type and includes two ( network sections, with second harmonic-traps devices. The directional coupler has been realized with microstrip technology.

Link