Category Archives: Transmitter

AM transmitter

I am always interested in building radio circuits. am transmitter, for construction, I used copper clad boards and really like the construction, not neat though, I do remember that I sprayed thicker coats of lacquer on the board before laying the parts on it.

circuit diagram: circuit AM

WP_20160322_001

 

 

back panel

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BNC antenna       audio input     power DC 12V in

 

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I used my function generator for carrier signal

 

 

 

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added carrier signal generator (AVR MCU board)

Carrier signal generator program:

it is simple just a PWM code, 16bit timer module in fast PWM

//FUSE bits
/*
BODLEVEL = DISABLED
RSTDISBL = [ ]
DWEN = [ ]
SPIEN = [X]
WDTON = [ ]
EESAVE = [ ]
BOOTSZ = 2048W_3800
BOOTRST = [ ]
CKDIV8 = [ ]
CKOUT = [ ]
SUT_CKSEL = EXTFSXTAL_16KCK_14CK_4MS1

EXTENDED = 0xFF (valid)
HIGH = 0xD9 (valid)
LOW = 0xE7 (valid)
*/
#define F_CPU 16000000UL
#include "avr/io.h"
#include "avr/interrupt.h"
#include "avr/sleep.h"
#include "util/delay.h"
void timer1(void);
void timer1()
{
        /*
         configure the timer1 module fast PWM mode
         Freq_OCR1A_PWM = F_CPU /(N(1+top)) = 16MHz/1(1+top)
         top = ICR1  */
        
    TCCR1A |= 1<<COM1A0 | 1<<WGM10 | 1<<WGM11;
    TCCR1B |= 1<<WGM12 | 1<<WGM13; 
    TCCR1B |= 1<<CS10;
    ICR1 = 27.4;  
}

int main(void)
{
    DDRD = 0x00; 
    PORTD = 0x00; 
    DDRC = 0x00;
    PORTC = 0x00; 
    DDRB |= 1<<PINB1; // declaring PINB1 as output
    timer1(); 
    sei(); //enable interrupt
    while(1)
    { 
        OCR1A = ICR1/2; //50% duty cycle
    }
}

we can also use schmitt trigger for this simple application, i used micrcontroller because i will include SWR meter in the future.
 

 

WP_20160325_004

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ah yes i know the circuit construction looks really bad, it is working 😀

 

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antenna coil (loop)

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antenna coil (loop)

i used this Loop antenna and with low power works really good

F0000TEK - Copy

signal across antenna coil

 

Video