FIXING THE POWER DISCREPANCY BETWEEN UPPER AND LOWER SIDEBAND MODES
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In tx_process() the following allows for fixing the reduced power in USB modes (and associated CW mode). The use of a multiplier of 1.4 causes the POWER to be increased by the square of 1.4 (or approximately twice, 3dB). This was determined after overall measurements of the power for CW and CWR at various pitches demonstrated the amount by which there was ripple in the crystal filter.? ?YOUR FILTER MAY BE DIFFERENT.? ?CHECK THE POWER LEVEL BETWEEN CW AND CWR AT SEVERAL PITCHES AND THEREBY MEASURE THE RIPPLE INYOUR CYRSTAL FILTER.? ?TAKE THE SQUARE ROOT OF THE TYPICAL POWER RATIO AND USE THAT TO MAKE THE CORRECTION IN THE CODE AS SHOWN BELOW.
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if (r->mode == MODE_LSB || r->mode == MODE_CWR)
// zero out the LSB
for (i = 0; i < MAX_BINS/2; i++){
__real__ fft_out[i] = 0;
__imag__ fft_out[i] = 0;
}
else
{ // zero out the USB
for (i = MAX_BINS/2; i < MAX_BINS; i++){
__real__ fft_out[i] = 0;
__imag__ fft_out[i] = 0;
}
// GLG: double the eventual USB signal to make up for unknown losses
for (i = 0; i < MAX_BINS/2; i++){
__real__ fft_out[i] = __real__ fft_out[i] * 1.4;
__imag__ fft_out[i] = __imag__ fft_out[i] * 1.4;
}
}
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