[Elecraft] Elecraft CW Net Announcement

[kevin]

Good Evening,

    I have been exercising my ears this week.  I bought a new set of 
speakers * and a sub-woofer  * so I had to check them out.  I started 
with a variety of types of music.  Then I wanted to test the specs.  A 
variable sound generator would be good but I didn't have one.  I could 
build one but laziness kicked in.  "I can do this" (hubris).  "I can do 
this now" (impatience).  All three traits triggered at once, so I wrote 
one instead.  *

    A few hours later my hubris had been tempered; sound drivers are dry 
reading.  Then I had a sine wave of a single frequency for ten seconds.  
Creating 44,100 samples per second was good enough. Then I swept the 
frequency from low to high for one minute. Fourier suggested I add a few 
sines or cosines together.  That created beat notes and resonances.  I 
now know the resonant frequencies of my house, various appliances, and 
my sinuses.

    The sun is tossing streams of gas at us this week.  A few more are 
due to hit tomorrow and Monday.  Depending on the timing, conditions 
could deteriorate quickly.  There is also another Sunday activity which 
may or may not affect attendance.  However, my ears are feeling pretty 
good about life so CW should be soothing, even over the hiss of the sun.


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




-



* code snippet

float freq = 17.f;
float incr_freq = 0.00002f;
int seconds = 300;
unsigned sample_rate = 44100;
double my_pi = 3.14159;
size_t buf_size = seconds * sample_rate;

// allocate PCM audio buffer
short * samples = malloc(sizeof(short) * buf_size);

for( int i=0; i<buf_size; ++i)
    {
// samples[i]  = 3192 * sin( (2.f * my_pi * 5.19*freq)/sample_rate * i );
     samples[i]  = 5134 * sin( (2.f * my_pi * 0.90*freq)/sample_rate * i );
// samples[i] += 3097 * cos( (2.f * my_pi * 3.36*freq)/sample_rate * i );

     samples[i] += 3097 * sin( (2.f * my_pi * 151.0)/sample_rate * i );
     samples[i] += 3097 * cos( (2.f * my_pi * 20.60)/sample_rate * i );

    freq += incr_freq;  //  sweep frequency just to make things interesting
/*
    if (17.0 > freq || freq > 1550.0)
       {
       incr_freq *= -1.0f;  // toggle direction of freq increment
       }
*/
    }



* 
https://audioengineusa.com/shop/wirelessspeakers/a2-wireless-computer-speakers/

* https://audioengineusa.com/shop/subwoofers/s6-compact-powered-subwoofer/