4
West Mountain Radio
Operating Manual
Operating
CLRdsp is easy to operate. When power is supplied to the CLRdsp, the CLIP LED
will turn green to indicate the unit is on.
The front panel “Filtering’ control allows continuous DSP level adjustment. When
turned fully counterclockwise, the DSP is bypassed. When turned fully clockwise,
maximum DSP filtering is realized. Maximum filtering is rarely needed during use.
A recommended setting is at the 10 - 12 o’clock position for typical HF channel
conditions. If the unit is powered up and the filtering knob is fully clockwise, the
firmware version is reported in Morse Code.
If the incoming audio level is too high the CLIP LED will flash. Reduce the input
just below flashing. Clipping disrupts the noise reduction circuit.
Noise Reduction Performance
The noise reduction is dynamic and adaptive. It senses the random character of
the voice or CW and permits it to pass through. The repetitive nature of the noise
is sensed and reduced according to the patented algorithms. Take notice of the
DSP battling the difference between the voice and the noise when both are at
equal level and the noise is constantly varying.
When the signal is CW, its intermittent character is sensed and the CW is passed
through. The noise is attenuated. When the noise is steady, such as a heterodyne
from a 40 meter broadcast station (carrier whistle), it is attenuated greatly to over
50 dB or about 0.003 times the original value. If the noise is a varying siren, it is
greatly reduced as well, but not as much as a heterodyne.
Transient sounds are greatly reduced, especially if they are repetitious. The net
effect of the Digital Signal Processor is to reduce atmospheric noise, static, hiss,
ignition noise, power line noise, carriers, hum, and heterodynes, while passing
voice and CW signals.
The adaptive nature of the noise reduction is apparent by observing its convergent
time. A single audible tone will vanish in about 1 second. White noise diminishes
in 1 to 2 seconds. Typical car noise and emergency alarms take about 2 seconds
to reduce.
Power Amplifier
CLRdsp contains a power amplifier integrated circuit. It produces 7.5 watts RMS
maximum into an 8 ohm loudspeaker, when connected to a 13.8 volt DC source.
The voltage gain is 46 dB typically. The amplifier has protection from a shorted
speaker.
