Satellite antenna grounding

[Leonard Caillouet]

I continue to see satellite receiver installations that are not grounded to
the electrical service ground or any other ground at all. I thought the NEC
was pretty clear that they must be grounded. Is there something that I
don't know? I service TVs all the time and encourage people to check the
grounding on the electrical service regularly. I often check them for
clients and notice that antenna and sat, sometimes cable are not grounded at
all. Antenna installers seem to be better about it, and cable installations
are better than they once were on this matter, but very few of the sat
antennas are grounded. What am I missing?

I just serviced a commercial installation in a medical facility and found
the same thing on the Direct TV installation. Checking the continuity b/w
the coax shield and the ac ground found an open ( in the Mohm range) with
about 8 volts induced ac. The leakage current was under the limit of 500
microamps, but shouldn't the damned system be grounded?

What has me wondering is that I see it so often.

Leonard

 

[Jeff Wiseman]

I continue to see satellite receiver installations that are not grounded to
the electrical service ground or any other ground at all. I thought the NEC
was pretty clear that they must be grounded. Is there something that I
don't know? I service TVs all the time and encourage people to check the
grounding on the electrical service regularly. I often check them for
clients and notice that antenna and sat, sometimes cable are not grounded at
all. Antenna installers seem to be better about it, and cable installations
are better than they once were on this matter, but very few of the sat
antennas are grounded. What am I missing?

I'm not super familiar with dish grounding requirements but I'm
pretty sure that minimally, the shield of the coax needs to be
grounded at its service entrance and that needs to be the same
place as your power's service entrance ground. There are some
issues about grounding the shields at the dish and the dish's
metal mount, etc., but I can't remember those (e.g., it may be
required that the mast of the dish is NOT grounded, etc.)

I just serviced a commercial installation in a medical facility and found
the same thing on the Direct TV installation. Checking the continuity b/w
the coax shield and the ac ground found an open ( in the Mohm range) with
about 8 volts induced ac. The leakage current was under the limit of 500
microamps, but shouldn't the damned system be grounded?

What has me wondering is that I see it so often.

What you are seeing might be a Red Herring for you. In order to
avoid ground loops in the system, there may be coaxial isolation
transformers on the coax feeds within the facility. Distribution
amps may also provide DC and power line frequency isolation on
the shield to reduce ground loops. These would break the DC
connectivity along the shield within the facility which is a
desireable thing. It is not a requirement that the shield on coax
provide an AC power protection ground--the ground wire for the
power wiring is for this.

As far as I know there is no requirement (or need) for DC
connectivity along a coax shield WITHIN a facility to that
facility's service entrance ground. The shield on the cable only
needs to be an RF ground. Making it a DC ground can be
counter-productive in MANY applications.

A proper test would be a conductivity test from the cable shield
at the Dish itself to the serivce entrance ground post. This
assumes that there is no arrestor equipment providing that
connectivity which could make it appear as though that link was
open too (e.g., like on your telephone line entrance where a low
voltage DC connection to ground isn't provided).

If I've misstated something here I welcome any corrections.

- Jeff

 

[Leonard Caillouet]

I think you are right on, Jeff, not misstating anything. There was no
ground from the dish or the coax coming into the building nor anywhere that
I could find inside. There were no isolation transformers that I could see,
just a switch and splitters.

I don't see the isolation of the shield at the receiver as necessarily being
a problem, and since the leakage both ways was acceptable, that is not an
issue, but the lack of grounding at the entrance is what puzzles me. The
reason that I wonder if there is something that I don't know is that most of
the sat installs that I see are not grounded. In practice it might not be a
big issue, since the geometry of the dish will not make it an effective
lightning rod, but it seems that leaving it ungrounded is just asking for
trouble. Also, it appears to be a code violation to me, if the coax
entering the building is not grounded to the electrical service ground rod.

Any satellite installers out there?

Leonard

 

[electrictym]

snipped:

I continue to see satellite receiver installations that are not grounded to

clients and notice that antenna and sat, sometimes cable are not grounded at
all. Antenna installers seem to be better about it, and cable installations
are better than they once were on this matter, but very few of the sat
antennas are grounded. What am I missing?

microamps, but shouldn't the damned system be grounded?

Leonard

+ + + + + + + + + + +


YES ..... according to just about any code.... it must be grounded.
A quick glance at the Dish Network or Direct TV user installation
guides will indicate safety grounding procedures.

 

[TOM]

Here's the kind of grounding block you want:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=090-338

Specially designed for type-f connectors, provides a code compliant
compression
ground connection.

By the way - putting a grounding connection right at the TV receiver and
bonding to the
AC power ground right at the receiver also significantly reduces
interference problems because it
drastically reduces the common-mode cable impedance at the TV set.

-- Tom

 

[Robotron Tom]

Leonard Caillouet started a controversy when he said... :

I think you are right on, Jeff, not misstating anything. There was no
ground from the dish or the coax coming into the building nor anywhere
that I could find inside. There were no isolation transformers that I
could see, just a switch and splitters.

I don't see the isolation of the shield at the receiver as necessarily
being a problem, and since the leakage both ways was acceptable, that
is not an issue, but the lack of grounding at the entrance is what
puzzles me. The reason that I wonder if there is something that I
don't know is that most of the sat installs that I see are not
grounded. In practice it might not be a big issue, since the geometry
of the dish will not make it an effective lightning rod, but it seems
that leaving it ungrounded is just asking for trouble. Also, it
appears to be a code violation to me, if the coax entering the
building is not grounded to the electrical service ground rod.

Any satellite installers out there?

Leonard

I'm not an istaller, but I did install my own satellite system. In the
instructions, there was a connection to earth ground at the junction
block, which looks like a splitter but isn't. That would make it shield
to ground.

Perhaps you miss this ground block, which would be somewhere inline.

Did you trace it from dish to receiver?

--
Robotron Tom *remove nospam to email*
See the Flashback Arcade at: http:// www.arcadeguy.net

Standing for right when it is unpopular is a true test of moral
character.
-M. Smith

 

[Jeff Wiseman]

Here's the kind of grounding block you want:

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=090-338

Specially designed for type-f connectors, provides a code compliant
compression
ground connection.

By the way - putting a grounding connection right at the TV receiver and
bonding to the
AC power ground right at the receiver also significantly reduces
interference problems because it
drastically reduces the common-mode cable impedance at the TV set.

-- Tom

I think that that is only partially true. Having a second ground
at the set that is not DIRECTLY connected to the power ground at
the sme set is guaranteed to create a ground loop. Some sets by
themselves can ignore this but other equipment such as home
theater stuff very frequently ends up being sensitive to it
resulting in humming througout the audio system.

- Jeff

 

[ron]

to expect all dish installs to be grounded to the utility ground is
wishful thinking..it would eliminate a large percentage of installs
due to the inability to install the dish near enough to that ground...
most installers will at least install a ground rod of their own, so
that there is some grounding, albeit that isn't to "code" though..
alot of newer homes, you will never find that ground rod as the
service is all underground and nothing is visible..unless the code is
strictly enforced, installers will cut corners to keep their jobs...

 

[Leonard Caillouet]

That is what I assume is going on. The curious thing is that not only are a
few not grounded, but virtually none that I check are grounded at all.

Leonard