Improper connector installation plagues many ham stations, not only with RG-6
CATV
connectors but with all types of coaxial connectors. An improperly installed
connector
is an invitation to RFI ingress and equipment damage.
At transmit power levels, an improperly installed connector can cause equipment
damage.
If you're not confident in your connector installation skills, its worth a few
dollars to have
them professionally installed.
Quad cable connector installation requires skills and patience. Compounding the
problem,
hams often use connectors that are not intended for use with quad RG-6.
Quad cable connector installation involves five specific steps, each performed
carefully
and correctly:
1. Use an RG-6 stripping tool to remove the jacket. Inspect the braid wires to
be sure
none of the wires are damaged. Never use a knife to remove the jacket,
inevitably it
will damage the fragile braid wires no matter how careful you are.
2. Carefully fold back only the outer braid and spread the braid wires evenly
around
the circumference of the cable jacket. Verify that no wires are broken. All of
the
braid wires should lay flat over the jacket, should not be more than 1/4 inch
long,
and should not be bunched up.
3. Remove the foil tape between the two braid shields. Do not use a knife to
assist
in foil tape removal. This step is time consuming and often ignored. The
connector
will be very difficult to install if the foil tape is not removed. If somehow
you manage
to force the connector onto the cable with the foil tape in place, the
connector will
be intermittent and unreliable.
4. Carefully fold back the inner braid and spread the braid wires evenly around
the circumference of the cable jacket. Verify that no wires are broken. All of
the
braid wires should lay flat over the jacket, should not be more than 1/4 inch
long,
and should not be bunched up.
5. Install the proper connector for quad shield cable. Be sure the connector is
fully
seated. If you need to use great force to mate the connector something is
wrong,
either you used the wrong connector or the cable was improperly prepared . If
somehow you manage to force the connector onto the cable, the connector will
be intermittent and unreliable.
Improper connector installation is so pervasive in the cable TV industry that
CommScope prepared an illustrated paper on improper connector installation.
http://docs.commscope.com/Public/ImproperQuadPrep.pdf
73
Frank
W3LPL
----- Original Message -----
From: "Paul Christensen" <w9ac@arrl.net>
To: "topband" <topband@contesting.com>
Sent: Tuesday, May 7, 2013 3:33:00 PM
Subject: Re: Topband: Problem with compression F connectors on Quad RG-6
> The standard drop cable is a bonded foil with single braid, it has been
> that way since the late 1970's. The current best grade is "Brightwire" by
> CommScope. Any good cable will far exceed FCC specs without a quad shield.
It remained that way with Comcast & AT&T Broadband at least until 2002 when
I left AT&T corporate engineering, shortly after the merger. I doubt much
has changed since then.
Concerns are a bit different in the broadband world where downstream leakage
must be minimized between 50 MHz - 1 GHz. The upstream path is in HF
region, but no sane cable operator uses spectrum below about 10 MHz. The
only services anywhere near that area of spectrum are used for data
transponders and IPPV from the set-top box where modulation is almost always
QPSK. Telephony and DOCSIS cable modem service is all relegated to an area
above 20 MHz. In the Jacksonville Comcast system, it's now all above 30 MHz
which was made possible through the use of tighter diplexer specs in the
system amps and fiber-optic nodes. if you could see a spectrum analyzer
display of the return path back at the headend, you would be amazed that the
return path works at all. Any point of ingress results high levels of
interference, most notably SWBC.
I recall writing up a paper in the mid-'90s that predicted a need for better
return path certification and an upward move of the lowest usable frequency
to well above 20 MHz. I pointed to the 11-year sunspot cycle as an
important driver. The non-ham engineers in our group didn't get it. But
the CTO of MediaOne was a ham, and he did get it. The public did not know
it, but there was a real fear between 1995 and 2000 that return path
broadband technology would never work. When you consider all the points of
potential failure, especially on a power-passing system, it truly is a
miracle that it works at all. Consider this: The typical fiber-optic node
services between 200-500 home passings. From the comfort of your living
room, and with an RF signal generator, one can wipe out an entire service
area when the return path frequencies of the system are known. This isn't
theoretical, I demonstrated the impact to a sober group of engineers with an
Eico generator. That potential still exists today.
Concerning SANS connectors and wiring, I would take the lead from the cable
operators. They cannot afford to have unreliable cables anywhere between
the customer equipment and the headend or hub facilities. When you've got
thousands of miles of cable plant and interfacing hardware, that becomes the
most important piece in the network. If a router, modulator or fiber amp
fails in the system, the fix is easy with money. But if you deploy bad
cable and hardware into a system, you'll feel the pain a long time as it
affects long-term service call volume, unhappy customers, and angry
government leaders who generally hate the cable operators.
Paul, W9AC
All good topband ops know fine whiskey is a daylight beverage.
_________________
Topband Reflector
All good topband ops know fine whiskey is a daylight beverage.
_________________
Topband Reflector
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