MFJ MFJ-784B, Инструкция по эксплуатации, Страница: 37 / 74

MFJ-784B Instruction Manual
Operation Error! Main Document Only. -11
Auto Notch Button
The auto notch does nearly the same job as the manual notch except it finds
and removes up to four unwanted tones very effectively. The main advantage
of the auto notch is that it hunts down and removes steady tones without any
help from you. The auto notch operates
only in the LR/HR, BP, 2BP, and SSB
filters regardless of whether they are saved in memory or not.
With the
Auto Notch button "in," the MFJ-784B searches for heterodynes or
steady tones and instantly removes them. It is so good it can remove four
drifting tones at the same time, even if the tones are moving in different
directions.
The automatic
notch filter has two important limitations. First, it cannot tell the
difference between a good tone and a bad tone. Some Filter positions are
used for receiving tone signals and the auto notch wouldn't have any idea
which tone you really want to copy. Therefore, we can't let you use the auto
notch in the following
Filters switch positions: CW, RTTY, HF PACKET, AMTOR,
PACTOR, and SSTV/FAX/WeFAX. In these modes the auto notch would
remove every signal, not just the bad ones.
Second, the automatic notch cannot tell the difference between a voice and a
tone that varies rapidly in volume and pitch. If we made the automatic notch
remove all the very fast changing tones, it would also remove tones from
voices. If we made the automatic notch work only on the slowest changing
tones, it would not follow the drifting or fading tones you didn't want to hear.
Because of this limited operating range, we give you two ways to select how
quickly and completely the automatic notch works.
One way you can control the notch speed is by reducing the volume control on
your receiver slightly. This will lower any distortion on voices while the
automatic notch is being used.
The second way to adjust the automatic notch involves removing the DSP's
cover and moving two jumpers to different positions. This adjustment allows
you to choose four different levels of what we call auto notch aggressiveness.
We ship the DSP in the least aggressive setting (1). If you are unhappy with the
notch and would like to step the notch performance up a little bit, you can
reset the jumpers. Refer to Jumper Settings on page 4-8. Remember that the
automatic notch's distortion of voices will get worse if you choose a more
aggressive setting.