This is a 1 Watt FM Transmitter power amplifier
design with a decent outline that can be utilized to open up a RF signal in the 88 – 108 MHz band. It is exceptionally delicate on the off chance that you utilize great RF power enhancer transistors, trimmers and curls. It has a force intensification component of 9 to 12 dB (9 to 15 times). At a data force of 100 mW the yield will be 1 Watt. You should pick T1 transistor based on connected voltage. In the event that you have a 12V DC power supply then utilize transistors like: 2N4427, KT920A, KT934A, KT904, BLX65, 2SC1970, BLY87. At 18 to 24V DC power supply you should use transistors like: 2N3866, 2N3553, KT922A, BLY91, BLX92A. You might utilize 2N2219 at 12V yet you will get a yield force of 0.4W most extreme.
Component list
R1 = 100Ω
R2 = 2.2KΩ at 12V and 4.7kΩ at 24V
R3 = 10KΩ
R4 = 100Ω
C1 = C5 = C6 = 10 – 60pF
C2 = C4 = 1nF
C3 = 10uF
D1 = 1N4148
L1 = 20 turns of 0.2mm = 36 SWG winding wire over R4
L2 = 7 turns of 0.8mm =21 SWG winding wire 6mm diameter on air core
L3 = 4 turns of 0.8mm =21 SWG winding wire 7mm diameter on air core
T1 = 2N4427, KT920A, KT934A, KT904, BLX65, 2SC1970, BLY87 (2N2219, for output of 0.4W) at 12V
T1 = 2N3866, 2N3553, KT922A, BLY91, BLX92A at 24V
Adjustment of the 1 watt fm power amp
Try not to interface any RF source now , but simply apply the DC supply and measure the voltage at point 1. Alter R3 until you measure 0.7V. Do not connect antenna now but connect 2 x 100 Ω 0.5W resistors in parallel at the RF yield. Then only connect the input rf that you have to increase the power
Gradually turn the C1 with a specific end goal to get the most possible voltage on the rf test . Then again try R3 to get 0.7 V at point 1. Presently modify C5 and C6 for most extreme yield voltage (must be between 12V to 18V).
Check the temperature of T1′s heatsink, if not badly heated it is alright.Then disconnect the DC supply, disengage the 2 resistors of 100 Ω and associate the receiving wire (keep the test joined). Apply the DC and now change again C1, C5 and C6 for greatest voltage sign on the test.
You might utilize an amp meter keeping in mind the end goal to check the present move through T1. This must not surpass 150mA at 12V and 100mA at 24V or the transistor will fail. L2 and L3 loops must have an edge of 90 degrees between them.