Spectrum DSP M2 User Manual V1.1
• ALC Release Time: This sets the time, after audio has dropped below the current
threshold, that the ALC will take to release and reduce attenuation. When set to the
default setting of 10, the ALC will have only a modest effect on the transmitted audio,
taking several seconds for the ALC to completely recover from a voice peak while
setting it to the maximum value if 20, the effect is almost that of disabling the ALC
entirely in terms of added compression in that the gain recovery rate is approximately
1dB/second. Low values (below 5) will “follow” audio very quickly and offer effectively
very high compression rate.
Warnings: (set-up dependent)
• Do not set the Mic/Line gain such that the peak audio level on the AUDIO meter
regularly peaks much above 4 to 8B, although occasional peaks to +10 are fine.
Avoid settings that “peg” the meter as this could result clipping and audio distortion.
• If the RF amplifier is working properly and not being overdriven, input audio
clipping should not cause “splattering” on the transmitted signal, only “bad”
sounding audio.
REMEMBER:
If your RF power meter does not have a "Peak" reading function specifically designed to read
PEP on SSB signals (many do not!) it will always give a false "low" power reading on SSB,
which is to say that your power on voice peaks may be where it should be, but your meter will
be reading a much lower pseudo-average!
Amplitude Modulation (AM) mode reception and transmission:
Receive “Frequency Translation” or offset mathematically shifts the center frequency by +12
kHz, depending on the setting of menu item “RX/TX Freq Xlate”. This function solves the
problem of the “Zero Hertz” hole that would otherwise cause a nulling of the AM carrier if the
receiver were tuned such that it were placed in the center of the receiver's passband. For
more information on this problem, see the information later in this section.
If “RX/TX Freq Xlate” is enabled, there are no special considerations that need to be taken
when tuning an AM signal other than those noted in the section below regarding the narrow
AM filtering.
Note: When offset-tuning and AM signal using the wide bandwidth filter mode with frequency
translate mode active, it is possible, when off-tuning by 12 kHz to place the AM carrier in the
“Zero Hertz” hole, resulting in distortion of the received signal.
Tuning AM signals with wide and narrow filtering:
The AM bandwidth filtering operates as follows. The bandwidths noted below are always
available in AM, regardless of menu settings:
There is one “wide” bandwidth and several different bandwidths are available for this setting:
P 54
To Next Page
Loading...