The personal website of Scott W Harden

New Transmitter, New Spots!

These should speak for themselves. Which signal is mine? Obviously I'm the crazy person who thinks it's funny to merge molecular biology with amateur radio.

Belgium JO10UX

England G4CWX

France JN39AB

Massachusetts W1BW

Nevada KK7CC

Netherlands JO22DA

Alaska KL1X

Italia I2NDT

New Zealand ZL2IK

Germany DL4MGM

This article's source was last edited on September 10, 2020.
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⚠️ Warning: This article is obsolete.
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QRSS DNA

I'm still working on this project, and although progress is slow I'm learning a lot and the circuit is getting better with time. I'm still not yet ready to post the schematics, but you can get an idea of what's going on from the picture. It can handle 255 levels of frequency shift and has the ability to turn the tone on and off. 6 capacitors, 3 resistors, 4 transistors, a single inductor, and a micro-controller.

UPDATE I spotted myself on W4BHK's Grabber about 300 miles away...

#include <avr /io.h>
#include <util /delay.h>

char dotlen = 5;                              // ultimately the speeed of transmission
char call[] = {0, 1, 1, 1, 2, 0, 2, 1, 1, 0}; // 0 for space, 1 for dit, 2 for dah

void setfor(char freq, char ticks)
{
    OCR1A = freq;
    while (ticks > 0)
    {
        sleep();
        ticks--;
    }
}

void sleep()
{
    for (char i = 0; i < dotlen; i++)
    {
        _delay_loop_2(65000);
    }
}

void slideto(char freq, char ticks)
{
    freq = freq + 30;
    char step = 1;
    if (OCR1A > freq)
    {
        step = -1;
    }
    while (OCR1A != freq)
    {
        OCR1A += step;
        setfor(OCR1A, 1);
    }
    setfor(freq, ticks);
}

void DNA()
{
    char a[] = {4, 5, 5, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 8, 7, 7, 7, 7, 6, 6, 6, 5, 5, 4, 3, 3, 2, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3};
    char b[] = {1, 1, 1, 1, 2, 2, 2, 3, 3, 4, 5, 5, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 8, 7, 7, 7, 7, 6, 6, 6, 5, 5, 4, 3, 3, 2, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0};
    for (char i = 0; i < sizeof(a); i++)
    {
        //slideto(a[i]*4,2);
        //slideto(b[i]*4,2);
        setfor(a[i] * 2 + 5, 10);
        setfor(b[i] * 2 + 5, 10);
    }
}

void ID()
{
    for (char i = 0; i < sizeof(call); i++)
    {
        setfor(10, 50);
        if (call[i] == 0)
        {
            setfor(10, 100);
        }
        if (call[i] == 1)
        {
            setfor(15, 100);
        }
        if (call[i] == 2)
        {
            setfor(15, 250);
        }
        setfor(10, 50);
    }
}

void ID2()
{
    for (char i = 0; i < sizeof(call); i++)
    {
        if (call[i] == 0)
        {
            ampOFF();
            setfor(10, 50);
        }
        if (call[i] == 1)
        {
            ampON();
            setfor(10, 100);
        }
        if (call[i] == 2)
        {
            ampON();
            setfor(13, 100);
        }
        ampOFF();
        setfor(OCR1A, 30);
    }
    ampON();
}

void ampON()
{
    PORTA |= (1 << PA7);
    PORTA |= (1 << PA0);
    PORTA &= ~(1 << PA1);
    _delay_loop_2(10000);
}
void ampOFF()
{
    PORTA &= ~(1 << PA7);
    PORTA |= (1 << PA1);
    PORTA &= ~(1 << PA0);
    _delay_loop_2(10000);
}

int main(void)
{
    DDRA = 255;
    OCR1A = 75;
    TCCR1A = 0x81;
    TCCR1B = 1;
    while (1)
    {
        ID2();
        ID();
        for (char i = 0; i < 3; i++)
        {
            DNA();
        }
    }
}
This article's source was last edited on September 10, 2020.
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⚠️ Warning: This article is obsolete.
Articles typically receive this designation when the technology they describe is no longer relevant, code provided is later deemed to be of poor quality, or the topics discussed are better presented in future articles. Articles like this are retained for the sake of preservation, but their content should be critically assessed.

Soup Can MEPT

This page documents the progress of my MEPT (manned experimental propagation transmitter) endeavors. If you have questions, feel free to E-mail me! My contact information can be found by clicking the link on the right navigation menu.

The Soup-Can Transmitter

The Signal

The Spots

Florida

288.3 miles away (W4HBK) May 22, 2010

Massachusetts

1,075.5 miles away (W1BW) May 27, 2010

Belgium

4,496.3 miles away (ON5EX) May 27, 2010

Germany

4,869.2 miles away (DL4MGM) May 28, 2010

Essex

4,356.4 miles away (G6AVK) May 28, 2010

New Zealand

8,077.6 miles away (ZL2IK) May 29, 2010

This article's source was last edited on September 10, 2020.
Have something to say about this article? Let me know!
⚠️ Warning: This article is obsolete.
Articles typically receive this designation when the technology they describe is no longer relevant, code provided is later deemed to be of poor quality, or the topics discussed are better presented in future articles. Articles like this are retained for the sake of preservation, but their content should be critically assessed.

Measure QRP Radio Output Power with an Oscilloscope

I added a backlight to my oscilloscope! My o-scope's backlight hasn't worked since I got it (for $10), so I soldered-up a row of 9 orange LEDs (I had them in a big bag) and hooked them directly up to a 3v wall wart. In retrospect I wish I had a bunch of blue LEDs... but for now I can't get over how well this worked! Compare it to the images a few posts back - you can really see the grid lines now!

I know this is super-basic stuff for a lot of you all, but I haven't found a place online which CLEARLY documents this process, so I figured I'd toss-up a no-nonsense post which documents how I calculate the power output (in watts) of my QRP devices (i.e., QRSS MEPT) using an oscilloscope.

I think I have increased power output because I'm now powering my 74HC240 from this power supply (5v, 200A) rather than USB power (which still powers the microcontroller). Let's see!

There's the signal, and I haven't calibrated the grid squares (this thing shifts wildly) so I have to measure PPV (peak-to-peak voltage) in "squares". The PPV of this is about 5.3 squares.

I now use a function generator to create square waves at a convenient height. Using the same oscilloscope settings, I noticed that 10v square waves are about 7 squares high. My function generator isn't extremely accurate as you can see (very fuzzy) but this is a good approximation. I now know that my signal is 5.3/7*10 volts. The rest of the math is pictured here:

140mW - cool! It's not huge... but it's pretty good for what it is (a 2-chip transmitter). I'd like to take it up to a full watt... we'll see how it goes. My 74HC240 is totally mutilated. I accidentally broke off one of the legs, couldn't solder to it anymore, and thought I destroyed the chip. After getting distraught about a $0.51 component, I ripped ALL the legs off. Later I realized I was running out of these chips, and decided to try to revive it. I used a Dremel with an extremely small bit (similar to a quarter-round burr in dentistry) and drilled into the black casing of the microchip just above the metal contacts, allowing me enough surface area for solder to adhere to. I'm amazed it works! Now, to get more milliwatts and perhaps even watts...

This article's source was last edited on September 10, 2020.
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AJ4VD Gator Spotted in Essex, England

It's so awesome that such a small device can send such a low power signal so far away! Anyhow, the title says it all. Special thanks to G6AVK's "part time" grabber for capturing this awesome series. That's a 4356.4 mile trip on USB power! ha!

This article's source was last edited on September 10, 2020.
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