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getting close is the white powder that is a symptom of oxidation of
aluminum housings; often aluminum darkens when oxidation is
taking place. These instances can be due to port caps left off,
missing gaskets or gaskets which have slipped out of their channel,
warped or cracked housings or cracked or broken connectors. Seals
have to be air-tight, otherwise, normal heating/cooling cycles can
bring in moist air which dumps its moisture when the temperature
cools. One of the symptoms associated with CPD is hum in the
signal. This is due to the semi-conductor properties of some of the
junk which forms when connections oxidize.
CPD can also be a symptom when coax experiences annular cracks
(although usually the ingress is more noticeable than the CPD).
Technicians need to be able to associate seemingly “unconnected”
symptoms. For example, someone notices a minor amount of hum in
the picture of a customer; two blocks away error rates start going up
on a data modem or DMX box. Somewhere in the area you find a
connector cracked at the housing entry which has allowed moisture
entry and oxidation to occur. Note that this can and does happen to
F connectors in homes or institutions.
To solve such problems, the source of the moisture ingress needs to
be found and removed, the moisture removed and the oxidation or
corrosion removed. It’s likely to be cheaper, easier and faster to
remove and replace an entire device (tap, directional coupler or
amplifier) than to determine and fix the cause of the moisture
ingress. If a bad F connector is found, it is good practice to also
replace the device to which the F connector was attached. In the
case of F connectors, relocation of equipment to be out of the path of
water and/or use of higher cost F connectors with better water seals is
recommended (it’s silly to save 25 cents on an F connector and
generate a 50 dollar trouble call).”
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Summary of Contents for 3SR
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