A most difficult and costly problem
exists if the underground leak, located
in a feeder or trunk line, is caused by
extremely poor workmanship or inferi-
or materials. In the past, some con-
tractors were known to have construct-
ed cable systems poorly by using
below grade supplies which can handle
analog CATV, but are incapable of han-
dling advanced services. The best
solution to this problem, and also the
most costly, is to have the entire cable
system in that area replaced.
2-7
~ Damaged Cable Sheathing
Another form of damage occurs when
cracks, slices or holes form in the
cable sheath. Water enters the cable
through these holes, causing corro-
sion inside the cable. Even a tiny
hole in the sheath can suck water into
the cable. Water damage in foam
cable is less of a problem because
there are fewer tendencies for water
migration to occur with the solid foam
dielectric. However, in fused disk
cable, the water collects inside the
cable, where it corrodes the center
conductor and sheath. Water and fur-
ther corrosion can migrate (flow) up
or down the cable. The water
migrates and will find eventually the
connectors and center conductors.
Then it will also migrate along the
center conductors. Also when the
sheath is corroded enough you begin
to lose ground impedance
When checking for damage to the
coaxial cable, evaluate the following
chronic trouble spots:
• Always check for holes and possi-
ble water migration at or near
suspension clamps, bonding
clamps, span clamps, guy lines,
trees, and expansion loops.
• Pole hardware rub-through is a
major cause of cable damage.
Provide insulation to cable at rub
points by using straps and spac-
ers to prevent damage. Use tree
guard.
• Be extra careful with span clamps,
both at the pole and at mid-span.
Span clamps can cause problems
when carelessly installed.
• Down guys and overhead pole-to-
pole guys can come into contact
with the cable and eventually
wear through the cable sheath.
• Use tree guards to protect the
cable. Tree limbs and branches
can be a problem if trees are not
properly trimmed and the cable is
not properly insulated.
• Cable may be damaged by animal
chews (particularly squirrels).
• As with everything, a good cable
will degrade with age even though
it may show no visible damage.
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