User's Manual

Chapter 2. Installation and Configuration
2–18
070-20000750-01 Rev A
The same result screen as Figure 2-12 on page -16 will show and the result text file will be
updated.
Antenna Polarity
What are the options?
The Aperto Series 600 point-to-point system runs in two modes; fixed polarity mode and
diversity mode.
The polarity is Vertical or Horizontal. Vertical is usually a better choice in that it provides
a signal over longer distances. That is not due to the strength of the signal since both Ver-
tical and Horizontal are the same strength. This characteristic is due to the type of inter-
ference from environmental factors. If there is interference from other signals, Horizontal
may be a better choice.
Antenna Diversity allows the PW610 to check both the Vertical and Horizontal signals the
use the stronger of the two. The radio/antenna is installed at a 45 degree angle and
appears to be a diamond shape rather than a rectangle. This is done so the Vertical and
Horizontal signals are more available to the PW610. The PW620 will increase the number
of SYNC packets on the wireless frame when it is placed in diversity mode so that the
synchronization may be seen more regularly by the PW610. The SYNC packets are either
sent Vertically or Horizontally, thus the settings of Vertical diversity and Horizontal diver-
sity on the PW620.
When to use Antenna Diversity
Antenna Diversity does have a disadvantage when it comes to signal strength. We loose
3db of signal strength when we run in diversity mode. Therefore, it is not appropriate to
enable diversity when long distances of weak signals are encountered. When maximum
signal strength is required, use either Vertical or Horizontal polarity without diversity.
Antenna Diversity should be used when there is multipath or signal distortion due to phys-
ical interference such as buildings or trees or other vegetation.
Multipath is cause by a signal bouncing off of reflective surfaces. The antenna receive
many signals from the same source frame, but due to their reflection, they are delayed
and thus many offsetting signals. Aperto utilizes many techniques to isolate the strongest
signal in a multipath environment, one of which is Antenna Diversity. Another way to deal
with the multipath environment is antenna alignment of which you are already familiar. If
the SNR value is low after pointing the antenna as best you could in a non-diversity mode,
you should re-mount the PW610 antenna and try diversity mode.
Another indication that you should try diversity mode is that after your best attempt at
antenna pointing you receive disappointing throughput results.