User Manual

Exalt Installation and Management Guide
ExtendAir (TDD) Series Digital Microwave Radios
14 203591-002
2009-12-18
• Mode – It is desirable, but not always necessary, to match the mode for all collocated links.
• Bandwidth – It is desirable, but not always necessary, to match the bandwidth for all collocated
links.
For complex networks, an Exalt engineer should review multi-link networks before deployment as
several factors can optimize the network for desired performance.
Figure 4 illustrates two separate radios benefiting from synchronized GPS sources.
Figure 4 Synchronized GPS sources
Offset Timing
Manual control of offset timing is also allowed. This provides a means to delay the synchronization
signal using a user-defined offset. This is helpful when Exalt radios are near other devices operating in
the same frequency band that also use a timing source, such as GPS. The timing source to the Exalt
radios can be adjusted to match the other radio system timing source mechanism.
Offset timing can also optimize timing intervals for repeaters and backbones. As the distance of each
link results in a unique factor for speed-of-light transmission of the radio signal, a subsequent radio can
be delayed in timing so that the overall synchronization of radios is precisely maintained.
Offset timing can be adjusted in 1-ms intervals, from zero to the radio’s frame length setting. For
example, if using a 2-ms frame length, the offset timing can be set from zero up to 1999 ms.
When Sync is Lost
If the primary sync source (for example, the GPS source) signal is lost due to equipment failure, a
disconnected sync cable, loss of satellite link, or other condition, the radio is said to be flywheeling.
When flywheeling, the radio’s clock is free-running off internal clocking and is no longer
Note: When GPS Sync is enabled, link initiation typically takes 1 to 3 minutes to allow for
the radio to properly synchronize to the available GPS satellites.