WiNRADiO G65DDC User’s Guide
33
FSK
Frequency Shift Keying
UDM
User Definable Mode
In addition to the standard AM, LSB, USB, CW and FM modes, the
Excalibur
Sigma
receiver is equipped with several special modes,
AMS
,
ISB
,
DSB
,
DRM
,
FSK
and
UDM
.
AMS Mode
The
AMS
mode is used to improve reception quality of amplitude-modulated
signals, especially those affected by selective fading which occurs over a large
distance.
When the AMS mode is selected, special controls appear under the tuning tab,
making it possible to select one (or both) of the signal’s sidebands to achieve
optimum reception:
In the AMS mode, there is a certain "capture range", a frequency range within
which the receiver will "capture" the signal and achieve synchronization. If you
are tuning to a new signal, this initial capture (“
Tune capture range
”) is initially
quite wide, within plus or minus 1.5 kHz (default value) from the actual signal
frequency. This is to enable easy tuning by pointing and clicking near the peak
in the DDC1 spectrum, or dragging the filter passband area in the demodulator
spectrum.
Once locked to a signal, the capture range automatically reduces (“
Sync. lock
range
”) to plus or minus 50 Hz (default value) from the signal frequency. The
reason for such reduction is to avoid “kidnapping" of the synchronization
frequency by a nearby strong signal if the carrier signal fades, as may happen
especially with long-distance reception, due to ionospheric effects.
