How To Operate Diversity Reception (Flex-6600/M And Flex-6700 Only) - FlexRadio Systems FLEX-6000 SIGNATURE Series User Manual

FLEX-6000 Signature Series - SmartSDR for Windows Software User's Guide
23 HOW TO OPERATE DIVERSITY RECEPTION (FLEX-6600/M AND
FLEX-6700 ONLY)
Diversity Reception is a powerful method for improving the reliability of a message signal by using
two or more communication channels with different characteristics. Diversity is very useful to aid
reception in weak and fading (QSB) signal conditions. With optimally configured antennas, weak
signal QSB copy can be improved up to 75%.
Two common diversity methods are space and polarization. Both methods use separate antennas to
receive different versions of the same signal. The FLEX-6600/M and FLEX-6700 incorporate two fully
independent Spectral Capture Units (SCUs) that allow two separate antennas to be simultaneously
digitized. The analog to digital converters (ADCs) on the respective SCUs are driven from a single
clock source to provide stable synchronous reception.
Note: Since the FLEX-6500, FLEX-6400/M and FLEX-6300 use a single SCU, they are not capable of
diversity reception.
For best results, antennas should be de-correlated in some way so that fading on one antenna is likely
to be seen as increased signal strength on the other antenna. De-correlation can be accomplished by
using different types of antennas (dipole and vertical), using the same type antenna at wide spacing
(e.g. multiple wavelengths), or using the same antenna with different polarizations (horizontal and
vertical or right and left). The more de-correlated the antennas the better but even small amounts
can be beneficial. One interesting example of the application of circular polarization diversity on HF
is discussed in the December 2010 QST article, "Gimme an X, Gimme an O, What's that Spell? –
Radio."
The diversity implementation provided in SmartSDR is intended for use only with headphones. Two
Slice Receivers attached to separate antennas are automatically routed to the left and right ears so
that the brain can provide discrimination between the signals. The reason speakers are not used is
that they allow the signals to combine in the space between the speakers to cause undesirable peaks
and nulls in the sound. For example, slice A could be set to RXA and slice B to RXB.
To enable diversity, click the DIV button in the slice Audio drop down menu as shown below. This
will create a diversity slave slice locked to the same frequency as the master slice of the diversity pair.
As seen in the screen shot below after diversity has been enabled, a weak SSB signal has been tuned
on slice A attached to ANT1 and the slaved diversity slice B on ANT2 locked to the same frequency as
slice A.
Note: The RXA, RXB, and XVTR ports are also available for receiver inputs.
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