Good Evening,
After a rainy week today's sun felt good. Buds are starting to
expand. Daffodils are about four inches tall, just in time for the next
snow storm due late in the week. There was one day of fog and snow. It
was like a Turner painting in shades of gray.
The sun is active. We are in the middle of an ion stream. Signals
are OK but noise is high. The stream should still be present tomorrow.
The ionosphere is charged up. I expect signals to bounce well with
moderate to heavier QSB. Forty meters could get noisy as the sun sets.
Please join us on (or near):
14050 kHz at 2300z Sunday (3 PM PST Sunday)
7047 kHz at 0030z Monday (4:30 PM PST Sunday)
73,
Kevin. KD5ONS
-
I wanted to see what happens when you feed a sine wave into a doublet.
This code snippet inserts the signal at the center feed point and walks
it outward at each time step. When the signal hits the end of the wire
it bounces back, adding its level to the incoming level.
I used degrees to measure the length of the antenna. One half of a wave
is 180 degrees long (pi). A half wave dipole has two legs each 1/4
wavelength long or 90 degrees. When each leg is 90 or 180 degrees long
the antenna behaves as expected at resonance. Shorter or longer legs
display their odd behaviors. Some day I will add a user interface which
does not require me to recompile the code.
static int step = 1;
int s = 0; // sine[] index
bool flag = false; // speed flag
DWORD WINAPI wave( LPVOID pV ) // working function
{
int k;
RECT rct;
int xS, yS; // screen coordinates
int dx = 1;
int centerLine = HEIGHT/2;
while(TRUE) // City on the edge of forever
{
if (flag)
{
SleepEx( 3, FALSE ); // Passing the time,
drinking good wine
}
else
{
SleepEx( 40, FALSE ); // Scalosians slow to human
speeds
}
hdc = GetDC(hwnd);
SelectObject(bkhdc, bkBitmap); // create cool background gray
GetClientRect(hwnd, &rct);
FillRect(bkhdc, &rct, cBrush); // paint background
// shift each element[] value up/out the antenna
shift();
// at each time step fill the feed point from the sine[] buffer
element[0] = sine[s];
// step through sine[]
s += step;
if (s > 359)
{
s = 0;
flag = true; // sleep less
}
// sum outgoing element with incoming element
sum();
// fill display on both legs
for (int e=0; e<LENGTH; e++)
{
// mirror right leg into left leg
display[LENGTH - e - 1] = elem[e];
display[e + LENGTH ] = elem[e];
}
for (int i=0; i<LENGTH; i++)
{
k = 255 + (int) (0.6 * display[i].level); // determine
color index
SelectObject(bkhdc, pn[k].pen ); // choose appropriate pen
xS = Xtransform(0, WINDOWX, 10, WIDTH/2, i * dx + 50 );
yS = Ytransform(WINDOWY, 0, 10, HEIGHT, display[i].level +
centerLine);
MoveToEx(bkhdc, xS, yS, NULL);
MoveToEx(hdc, xS, yS, NULL);
xS = Xtransform(0, WINDOWX, 10, WIDTH/2, i * dx + 50 );
yS = Ytransform(WINDOWY, 0, 10, HEIGHT, centerLine );
LineTo(bkhdc, xS, yS);
LineTo(hdc, xS, yS);
}
for (int i=LENGTH; i<2*LENGTH; i++) // right leg
{
k = 255 + (int) (0.6 * display[i].level);
SelectObject(bkhdc, pn[k].pen );
xS = Xtransform(0, WINDOWX, 10, WIDTH/2, i * dx + 55 );
yS = Ytransform(WINDOWY, 0, 10, HEIGHT, display[i].level +
centerLine );
MoveToEx(bkhdc, xS, yS, NULL);
MoveToEx(hdc, xS, yS, NULL);
xS = Xtransform(0, WINDOWX, 10, WIDTH/2, i * dx + 55);
yS = Ytransform(WINDOWY, 0, 10, HEIGHT, centerLine );
LineTo(bkhdc, xS, yS);
LineTo(hdc, xS, yS);
}
// SelectObject(bkhdc, GetStockObject(BLACK_PEN));
ReleaseDC(hwnd, hdc);
InvalidateRect(hwnd, NULL, TRUE); // force WM_PAINT
}
ExitProcess( 0 );
return 0;
}
I will post the files, make file, and an exe on my web site. It is fun
to see what happens with non-resonant lengths.
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