RF Power Amplifier 1.3W to 6W by 2SC1970

This amplifier is based on the transistor 2SC1970 and 2N4427.
The output power is about 1.3W and the input driving power is 30-50mW.
You can use other transistor as 2SC1971 and get much more output power.
1.3W will still get your RF signal quit far and I advice you to use a good 50 ohm resistor as dummy load.
Make sure it can take up to 5-10W, else it will be a hot resistor.
You MUST use an antenna or 50 ohm dummy resistor while testing else you burn up the transistor.
In all RF system and specially in RF amplifiers, it is very important to have a stable power supply and making sure you won’t get any RF out on the power line. The Capacitor C12 and C13 will stabilise the DC power supply. L1, C10, C11 and L3 with C8, C9 will also prevent RF from leaking out to the powerline and cause oscillation or disturbances. L1 and L3 should be ferrite chokes or inductance’s about 1 to 10 uH.

Transistor Q1 will act as a buffer amplifier, because I don’t want to load the previous stage to much.
The input RF signal is passin C1 and F1 which is a small ferrite pearl where the wire just passing through.
F1 with C2 will act as an impedance matching for Q1.
F1 can be substituted with a coil as L4, but in my test I found that the ferrite pearls gave best performances.
L2 is nit a critical component and any coil from 2-10uH will do the job. Q1 will amplify the input signal from 50mW to about 200mW.
Q1 can amplify much more, but It doesn’t need to do that because 200mW is good for the final transistor.
If you want higher power you can decrease the resistor R2.

If you look at Q2 you will also find a ferrite pearl F2 at the base to emitter. This ferrite pearls is to set the DC voltage to zero and be a high impedance for RF signals. I wounded the wire 4 times around this small ferrite pearl. You can substitute it with a coil of 1uH or more.

C4, C5 and L4 forms an input matching unit for the transistor. Not much we can do about that…
At the output of the final transistor Q2 you will find 2 coils L5 and L6.
Together with C6 and C7, they form an impedance unit for the antenna and also for the transistor.

60W RF Linear amplifier

The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840. 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 IRF 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 circuit is very easy. Connect a dummy load to the out put of the circuit. You can use some small bulb like 24V 6Watts as the dummy load. I have even used 230V 60Watts 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 distroyed by self oscillation. So gate voltage must be below 2V and fixing at 1V will be safe.

Bifalar transformaer 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.Thank you

FM Transmitter 4W by 2N3553

This is a small but quite powerful FM transmitter having three RF stages incorporating an audio preamplifier for better modulation. t has an output power of 4 Watts and works off 12-18 VDC which makes it easily portable. It is the ideal project for the beginner who wishes to get started in the fascinating world of FM broadcasting and wants a good basic circuit to experiment with.

Technical Specifications – Characteristics

Modulation type: …….. FM
Frequency range: …. 88-108 MHz
Working voltage: ….. 12-18 VDC
Maximum current: ……. 450 mA
Output power: ………… 4 W

Parts List

TR1 = TR2 = 2N2219 NPN
TR3 = 2N3553 NPN
TR4 = BC547/BC548 NPN
D1 = 1N4148 diode *
MIC = crystalic microphone

40 Watt Amplifier For FM Broadcast by MRF171A

This amplifier was built based on Marconi’s website, A Design for a 40W broadband VHF RF Power Amplifier for FM broadcast. A few minor tweaks were made to the schematic and a few parts were changed to what I had available (mostly surface mount components). The heatsink is from an old Motorola Mostar 800 MHz radio, and has the perfect heatsink island to match the MRF171A. Also used is a Progressive Concepts external LPF7002 low pass filter because it was also on hand. Since the MOSFET uses 28 VDC, I had to homebrew a 28 Volt / 5 Amp power supply using the schematic found in the ARRL handbook.

Tune up went exactly as stated in the how-to, with the RF power output hitting 57 Watts when driven with a stock Broadcast Warehouse 1 Watt LCD PLL transmitter at 98 MHz. Liberal use of ferrite beads and feedthru capacitors are on all RF detector, fan control and SWR control circuits.

Linear FM 30Watt with BLY89

A amplifier of medium force RF for the FM, is always essential for the amateur that wants it strengthens some small transmitter, that likely it has already it manufactured! The present circuit can give force 25-30W, with control no bigger than 4-5 W.

As it appears in the analytic drawing, the amplifier is manufactured with the transistor TR1 of type LY89 of Phillips. The transistor this is specifically drawn for operation in frequencies up to 175Mhz, with very good results. His special characteristics appear below:


Tendency of operation: 18V
Current of Collector: max 3 5th
Gain: max 10dB
Force of Expense: 25-30 W
Output (order C): > 60%

Variable capacitors C1, C2, with inductor L1, constitute the coordinated circuit that adapts the exit of our transmitter in this amplifier RF. the circuit has been calculated suitably, so that it covers all band the FM with the biggest possible output. Inductor RFC1 polarize the transistor, so as to it works in order C that is to say with the biggest output. Inductor L2 in the collector of TR1, constitutes the charge of amplifier, while RFC2 prevents the RF signals escape in the line of catering. Capacitor C2 and resistance R1, protect the circuit from auto polarize.

The coordinated circuit of expense that is constituted by inductor L2 and variable capacitors C3, C4, adapts the exit of amplifier RF with the next stage that can be some amplifier RF of high force (> 100W) or a aerial.


MANUFACTURE

The manufacture of amplifier is very simple and easy. Puncture the point PCB that will pass the nutshell of TR1. Stick the capacitors, variable, the resistance, the RF tsok and the inductors. Finally you stick the TR1, being careful not overheats at the welding and blend pin his. Clean finally PCB from the residues of soldering. Make a very careful control for by any chance errors, omissions, short-circuits, chills you stick also anything other that could you make wonder why does not work the amplifier.

PARTS

C1, C2, C3, C4 = 10 -80pF

C 5 = 10nF

C6 = 1000pF

C7 = 100nF

C8 = 2200mF/35V

L1 = 1 coil with diameter of 10 mms, 1 mm

L2 = 7 coils with diameter of 10 mms, 0,8 mm

L3 = 3 coils with diameter of 10 mms, 1 mm

TR1 = BLY89

RFC = RF tsok




If all they are it includes, you connect the exit of your transmitter (3-4W) in the entry of amplifier. The exit of amplifier him you will connect in some charge (dummy load) or in the aerial, through a bridge stagnant. Be supplied with tendency 11-15V your amplifier. (Power supply it should it provides current 45th). Regulate the 4 variable (C1-C4, until you take the biggest force of expense. The amplifier is ready.

FM Stereo Transmitter with IC BA1404

You’ll find that this is a very easy project to build. It will transmit good quality sound in the FM band ( 88 – 108 mhz ). One inportant item is that the IC chip operates on 3 volts DC. The chip will get destroyed if it is operated on any voltage higher than 3.5 volts. The antenna can be a standard telescopic antenna or a 2 foot length of wire. The input is in the millivolt range and you may need to add additional pots for the inputs. I was able to use this circuit for a walkman and a portable CD player in my car. I used the headphone jack on both and varied the signal with the volume control.

To adjust the circuit tune your FM radio to a quite spot then adjust the trimmer capacitor C8 until you hear the signal that you are transmiting. When you have a strong signal adjust the resistor R4 until the stereo signal indicator lights. If the input is to high of a signal you may over drive the IC chip. Use two 15 turn pots on the input signals to bring the level down. You can balance the signal by using headphones. The inductor L1 is 3 turns of .5 mm wire on a 5 mm ferrite core.