Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
|
|||
|
|||
Satellite antenna grounding
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 |
#2
|
|||
|
|||
Leonard Caillouet wrote: 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 |
#3
|
|||
|
|||
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 "Jeff Wiseman" wrote in message ... Leonard Caillouet wrote: 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 |
#4
|
|||
|
|||
snipped:
"Leonard Caillouet" wrote in message news: 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. |
#5
|
|||
|
|||
Here's the kind of grounding block you want:
http://www.partsexpress.com/pe/showd...number=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 "Leonard Caillouet" wrote in message news:2VNdd.39$jd.28@lakeread04... 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 |
#6
|
|||
|
|||
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 |
#7
|
|||
|
|||
TOM wrote: Here's the kind of grounding block you want: http://www.partsexpress.com/pe/showd...number=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 |
#8
|
|||
|
|||
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... Jeff Wiseman wrote in message ... TOM wrote: Here's the kind of grounding block you want: http://www.partsexpress.com/pe/showd...number=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 |
#9
|
|||
|
|||
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 "ron" wrote in message om... 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... Jeff Wiseman wrote in message ... TOM wrote: Here's the kind of grounding block you want: http://www.partsexpress.com/pe/showd...number=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 |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Antenna Grounding | Home Repair | |||
Microwave interferes with AM radio | Home Repair | |||
Grounding Rod *and* Rebar for service grounds? | Home Repair |