5-4
CSO Intermodulation products from forward path signals are
stronger in this previously unused band
B. What does it take to troubleshoot reverse path problems?
Troubleshooting noise in the reverse path is also trickier. It can
require five to ten times the time and energy, as well as being
infinitely more frustrating:
When a certain customer has a problem, there is a much wider area
that must be searched to find it. In the forward path, the problem
must be somewhere in the direct line from the customer to the
Headend. For a reverse path problem, it can be anywhere in the
entire area served by this customer’s receiver. This means there are
many more test points to check, a far greater possibility for error, and
much more money can be wasted if the problem remains incorrectly
diagnosed. The forward path technique of ‘walking back up the
system’ and replacing everything until the problem goes away simply
doesn’t work. You now MUST have a tool that accurately indicates
whether the problem is ‘here’ or ‘there.’
The sources of interference come and go. CB, ham, and mobile
transmitters are not continuous, and they move around. Switching
noise is transient, and may last only a few microseconds, but repeat
at irregular intervals and render a network useless.
To have any chance for successful in troubleshooting reverse noise
problems, you need a FAST (peak detecting) spectrum analysis
display. You need to be able to catch transient noise spikes. It is
also essential to be have a ‘peak hold’ capability so that a passing
burst can be captured and viewed. You can’t find the source of
something you can’t see. There is just too much ground to cover in
finding reverse path problems. These are the bare minimum criteria,
but many other tools can help ‘even the odds’ when a system does
battle with ingress.