Vectronics VEC-884 - Manual (Page 62)

VEC-884 Owner's Manual
Filter Description 5-10
Automatic Notch Filter
Use: Removes multiple tones or heterodynes quickly.
Removes up to 4 changing tones in the presence of speech signals.
The multiple automatic notch filter searches for and eliminates up to four
changing or shifting tones in milli-seconds, with attenuation as great as 50 dB.
All the notches are extremely narrow, resulting in a minimal effect on the voice
signals. The automatic
notch filter is disabled in the following filter modes:
CW, RTTY, HF PACKET, AMTOR, PACTOR, and SSTV/FAX/WeFAX (including
those stored in memory).
There is an adjustment to change the "speed" of the automatic notch filter.
We call this adjustment the automatic notch aggressiveness. By changing a
jumper setting, this aggressiveness can be changed in a range of four levels.
See the jumper setting section on page 4-8.
Noise Reduction Filter
Use: Removes random noises such as white noise, background hiss, etc.
Removes random noises and passes coherent signals like voices.
The random noise reduction filter effectively removes noises in the presence of
voice with minimal degradation of the voice itself. The noise reduction filter
works by automatically forming constantly-varying band-pass filters around the
coherent components, such as speech, of the audio signal. In effect, this
provides noise reduction by reducing the individual filters' bandwidths to the
minimum required to pass the speech signals intelligently. This filter greatly
reduces operator fatigue during long-term monitoring and makes listening
much more pleasant.
There is a noise reduction control to adjust the reduction characteristics of
the noise reduction filter to prevent signal distortion. When this control is in
the full clockwise position, random noises can be attenuated up to 20 dB
(depending on the types of noises).