Spectrum DSP M2 User Manual page 43

(e.g. a configuration to "attack" a tone very quickly) can also affect voice quality.
DSP Notch BufLen – This is the length of the De-Correlation delay buffer. In order for
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the DSP to tell a CW note from noise, it must have a sample of each, but given the
absence of a pristine noise source, we can "simulate" one by delaying the original
signal to "de-correlate" it. If we delay it too little, it will resemble the original signal too
much and be ineffective and start to affect voice. If it is increased, the notch becomes
more accurate, but it can slow down and, for a number of reasons, actually lose
effectiveness.
Noise Blanker related items:
NB AGC T/C (<=Slow) – This is the time constant for the noise blanker AGC and it
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may be adjusted in an effort to improve the performance of the AGC. A lower value
corresponds with a slower AGC within the noise blanker algorithm.
IMPORTANT: While you are in the menu system and it is being displayed, the noise blanker
is always disabled, so you must exit the menu to note the effect of that parameter!
Transmit audio related items: (set-up dependent)
AM TX Audio Filter – When set to "ON" this will insert a "brick wall" audio bandpass
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filter (275-2700 Hz, approx) in the audio transmit path – the same filter that is used on
SSB transmit. When set to "OFF" this filter is bypassed, allowing audio to be passed
below 100 Hz and somewhat above 3000 Hz, improving fidelity.
◦ Note that while fidelity is improved when this filter is turned off, "talk power" is
reduced as more transmit energy is devoted the parts of the voice that do not carry
information.
SSB TX Audio Filter – When set to "ON" this will insert a "brick wall" audio bandpass
•
filter (275-2700 Hz, approx) in the audio transmit path – the same filter that is used on
SSB transmit. When set to "OFF" this filter is bypassed, allowing audio to be passed
below 100 Hz and somewhat above 3000 Hz, improving fidelity.
◦ Note that while fidelity is improved when this filter is turned off, "talk power" is
reduced as more transmit energy is devoted the parts of the voice that do not carry
information.
◦ If the SSB audio filter is disabled, PLEASE be considerate of other users on the
amateur bands as your signal will also be "wider", extending both above 2.7 kHz
and also suffering somewhat in opposite-sideband rejection to approximately 200
kHz.
FFT Spectrum Scope and Waterfall related items:
FFT Windowing – The use of "FFT Windowing" - the pre-processing of spectral data
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before display – can greatly improve the visual performance of the Spectrum Scope
and Waterfall display by decreasing "bin leakage" (e.g. "sidelobe") - that is, the
Spectrum DSP M2 User Manual V1.1
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