# A simple USB radio script for BasicDSP
# By Niels PE1OIT, Nov 2008.
# 
# Slider 1 controls the frequency
# Slider 2 controls the volume

samplerate = 48000

# down-convert to 1st IF:
z = mod1(z+slider1);
ai = ini * cos1(z) - inq*sin1(z)
aq = inq * cos1(z) + ini*sin1(z)

# filter IF:
bi = biquad(ai, 0.0014603166, -1.8890331, 0.89487433, 2, 1)
ci = biquad(bi, 0.0014603166, -1.8890331, 0.89487433, 2, 1)
bq = biquad(aq, 0.0014603166, -1.8890331, 0.89487433, 2, 1)
cq = biquad(bq, 0.0014603166, -1.8890331, 0.89487433, 2, 1)

# down-convert to DC
y = mod1(y+0.0275)
audio = ci*cos1(y) + cq*sin1(y)

# AGC
x = audio*audio;
lvl = lvl * 0.999 + 0.001*x;
lvl2 = lvl2 * 0.9995 + 0.0005*lvl;
gain = 0.1 / (sqrt(lvl2) + 0.00001);

# output
uitL = audio * gain * slider2
uitR = audio * gain * slider2