Thursday, June 19, 2014

1.3W VHF RF Amplifier 2SC1970 88-108 MHz

 

     

    1.3W VHF RF Amplifier 2SC1970 88-108 MHz

    1.3W VHF RF Amplifier 2SC1970 88-108 MHz

     


    This RF power amplifier is based on the transistor 2SC1970 and 2N4427. The output power is about 1.3W and the input driving power is 30-50mW. It will still get your RF signal quit far and I advice you to use a good 50 ohm resistor as dummy load. To tune this amplifier you can either use a power meter/wattmeter, SWR unit or you can do using a RF field meter.

    1.3W VHF RF Amplifier 2SC1970 88-108 MHz

    RF Amplifier Assembly


    Good grounding is very important in a RF system. I use bottom layer as Ground and I connect it with the top with wires to get a good grounding. Make sure you have some cooling at the transistor. In my case I put the 2SC1970 close to the PCB to handle the heat. With good tuning the transistor shouldn't become hot.


    RF Amplifier Printed Circuit Board


    You can download a pdf file which is the black PCB. The PCB is mirrored because the printed side side should be faced down the board during UV exposure. To the right you will find a pic showing the assembly of all components on the same board.This is how the real board should look when you are going to solder the components. It is a board made for surface mounted components, so the copper is on the top layer. I am sure you can still use hole mounted components as well.
    Grey area is copper and each component is draw in different colors all to make it easy to identify for you. The scale of the pdf is 1:1 and the picture at right is magnified with 4 times. Click on the pic to enlarge it.


    Low-Pass Filter


    Some of you might want to add a low-pass filter at the output. I have not added any extra low pass filter in my construction because I don't think it is needed. You can easy find several homepages about low pass filter and how to build them.

    1.3W VHF RF Amplifier 2SC1970 88-108 MHz


2 comments:

  1. how do i can add this to my transmitter, while i dont know my transmitter power output . please help me how to determine the output power without wattmeter,,,

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  2. Aproximate FM Transmitter Range Vs. RF Power
    1 mW = 10 feet
    10 mW = 30 feet
    100 mW = 100 feet
    1 W = 1.5 Miles
    2 W = 2.1 Miles
    4 W = 3.0 Miles
    8 W = 4.2 Miles
    16 W = 6.0 Miles
    32 W = 8.6 Miles
    64 W = 12.0 Miles
    128 W = 17.0 Miles
    256 W = 24.0 Miles
    512 W = 34.0 Miles
    1 KW = 50.0 Miles

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