10
Noise Reduction and Heterodyne Elimination
To activate heterodyne/tone elimination and random noise reduction, depress the push-buttons
marked "NRt" and "NRr", respectively. Tone elimination , random noise reduction and
highpass/lowpass filtering can operate simultaneously or independently. Just depress the desired
combinations of push-buttons. One highpass/lowpass filter combination is always active in the
highpass/lowpass mode, so set the filters for the widest bandwidth for the best frequency
response.
To activate Variable Noise Reduction (VNR), depress the “NRr” button if the DSP-59+ isn’t
already in the random noise reduction mode. Then turn the High Pass control straight down to
the 6 o’clock position so that a tone is audible. Then turn the Low Pass control to adjust the
amount of random noise reduction. The High Pass filter setting is fixed at 300 Hz in the VNR
mode. The Low Pass filter frequency remains at its last setting before entering the VNR mode.
The DSP-59+ will stay in the VNR mode until the High Pass control is moved from the 6
o’clock position. When High Pass control is moved to turn off the VNR mode, the noise
reduction aggressiveness will remain at its last setting until it is changed or the DSP-59+ is
turned off.
Voice Bypass Mode
Depressing the Bypass push-button places the DSP-59+ into a bypass mode. In this mode, a
relay connects the audio input jack of the DSP-59+ directly to the speaker and headphone output
jacks. The relay also connects the audio input jack of the DSP-59+ to the line output jack via a 6
dB attenuator. The Bypass mode has precedence over the voice mode. When the DSP-59+ is in
bypass, the settings of the gain control and the parameter select push buttons do not affect the
signal. Turning off or removing power from the DSP-59+ automatically de-energizes the relay
and forces the DSP-59+ into the bypass mode.
SSB Operating Hint
Set the Highpass Filter to 300 Hz. and the Lowpass filter to 2.7 kHz. for normal sideband
operation. Adjust the Highpass filter up to 500 or 600 Hz. to eliminate heavy QRM, if
necessary. Adjust the Lowpass filter down to 1.9 kHz. to eliminate heavy QRM. Of course you
may set them anywhere you wish, but remember that extremely narrow bandwidths will affect
intelligibility, so keep the bandwidths wide, if possible.
