FLEX-6000 Signature Series - SmartSDR for Windows Software User’s Guide
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Copyright 2018 FlexRadio Systems. All Rights Reserved.
27.5 WEAK SIGNAL CONSIDERATIONS
When using SmartSDR for weak signal operations, three kinds of receivers will be in use: Panadapters,
Waterfalls and Slice Receivers. The noise floor of the Panadapter may be changed to facilitate seeing
signals that are weaker than the “noise floor.” Amateurs generally refer to the noise floor as the
noise floor in a 500Hz bandwidth receiver. For a SmartSDR Panadapter, the receiver is variable width
for a single “bin” or pixel in your display. The further you zoom in the Panadapter, the lower the bin
size in use and the lower the noise floor. The processing gain achieved in this way is 3dB for each
reduction in the bandwidth of a bin by two --- or each time the magnifying glass ‘+’ is depressed.
On a FLEX-6600/M or FLEX-6700, fully zoomed in, the bin size will be 1.5Hz. This represents a 25dB
gain over the 500Hz noise floor. The Waterfall and Panadapter both derive data from the same
receiver so for best weak signal viewing, zoom the Panadapter to one of the last few zoom levels. On
a FLEX-6500 or FLEX-6300, the minimum bin size is 5.9Hz.
The noise floor of the Slice Receiver is independent of the Panadapter and is adjustable by adjusting
the filter width of the Slice Receiver. Your ears and brain provide their own type of processing gain
and so the Slice Receiver should be adjusted for best listening experience. In general, the AGC-T
should be set to a low value for best listening on transverted bands. In other words, it should be
adjusted for a relatively quiet receiver.
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