HR21, grounding and SW hum

RobbinM · Mar 27, 2010

I've just reconfigured my system to run all components via HDMI into a new A/V receiver. My Subwoofer was a hum now. I tried unplugging various cables and find that it's the satellite receiver causing the hum.

If I unplug both coax cables, the hum stops. I've check the outside and both cables are grounded through a ground block, as is a wire that is attached to the satellite pole (it's a ground mount). The ground block is connected to the house ground rod.

I've made sure that the connections are all clean and tight going to the ground rod. This had the affect of increasing the hum. If I remove the ground wire, the hum goes completely away.

I'm out of ideas. Any help?

ebms1 · Mar 28, 2010

RobbinM said:
I've just reconfigured my system to run all components via HDMI into a new A/V receiver. My Subwoofer was a hum now. I tried unplugging various cables and find that it's the satellite receiver causing the hum.

If I unplug both coax cables, the hum stops. I've check the outside and both cables are grounded through a ground block, as is a wire that is attached to the satellite pole (it's a ground mount). The ground block is connected to the house ground rod.

I've made sure that the connections are all clean and tight going to the ground rod. This had the affect of increasing the hum. If I remove the ground wire, the hum goes completely away.

I'm out of ideas. Any help?

the first thing i would do is get a 3 wire tester & check that the wiring is correct to the outlets.... also check that the house grn is grounding correctly

delta_charlie · Mar 28, 2010

RobbinM said:
I've just reconfigured my system to run all components via HDMI into a new A/V receiver. My Subwoofer was a hum now. I tried unplugging various cables and find that it's the satellite receiver causing the hum.

If I unplug both coax cables, the hum stops. I've check the outside and both cables are grounded through a ground block, as is a wire that is attached to the satellite pole (it's a ground mount). The ground block is connected to the house ground rod.

I've made sure that the connections are all clean and tight going to the ground rod. This had the affect of increasing the hum. If I remove the ground wire, the hum goes completely away.

I'm out of ideas. Any help?

Hi, that sure sounds like a classic ground loop to me. My understanding on ground loops is they can occur when two or more ground rods are used. Are you sure there is only the one house ground? A google search on ground loop should pull up lot's more info. Hope this helps, DC

RobbinM · Mar 28, 2010

There is only one ground. I'll look into "ground loop" to see what I can learn. thanks.

raoul5788 · Mar 28, 2010

The dish should be grounded to the water feed where it comes into the house, if you have one, not the ground rod. It could also be the wiring in the outlet the HR21 is plugged into, like ebms1 suggested, or the one the sub is connected to.

wildbill129 · Mar 28, 2010

raoul5788 said:
The dish should be grounded to the water feed where it comes into the house, if you have one, not the ground rod. It could also be the wiring in the outlet the HR21 is plugged into, like ebms1 suggested, or the one the sub is connected to.

Chip,

The water line, if copper, and if it's tied to the house bond is an acceptable alternative to a ground rod tie in. It is not the preferred method. The preferred method is a direct tie in to the house bond at either the main panel, a sub panel, or the rod directly.

To the OP, how far is the pole from the house and the ground block? Is the ground block and the pole ground connected together? You do not want separate grounds, they must both be tied to the house bond. The ground rod you are talking about is the main house bond and not one that was added later during the dish install?

As others have said, make sure the outlet is properly grounded. Are all the components connected to the same outlet or power strip? If not, check the grounds on all of them.

RobbinM · Mar 28, 2010

wildbill129, I have one ground rod. It's right by the electric meter. The ground block for the sat is about 2 feet from the ground rod. The satellite pole is attached to the ground block along with the two coax cables.

The satellite doesn't have it's own ground.

All components are plugged into the same powerstrip, a monster power Powerbar 1100. It has indicator lights for ground status (green) and reversed wiring (not lit). That suggests the outline is good.

This is the confusing part. Everything seems like it should be OK. Could I have an applicance not working correctly and putting RF into the common ground?

raoul5788 · Mar 29, 2010

wildbill129 said:
Chip,

The water line, if copper, and if it's tied to the house bond is an acceptable alternative to a ground rod tie in. It is not the preferred method. The preferred method is a direct tie in to the house bond at either the main panel, a sub panel, or the rod directly.

To the OP, how far is the pole from the house and the ground block? Is the ground block and the pole ground connected together? You do not want separate grounds, they must both be tied to the house bond. The ground rod you are talking about is the main house bond and not one that was added later during the dish install?

As others have said, make sure the outlet is properly grounded. Are all the components connected to the same outlet or power strip? If not, check the grounds on all of them.

Actually, grounding to the water line is NEC code.

raoul5788 · Mar 29, 2010

RobbinM said:
wildbill129, I have one ground rod. It's right by the electric meter. The ground block for the sat is about 2 feet from the ground rod. The satellite pole is attached to the ground block along with the two coax cables.

The satellite doesn't have it's own ground.

All components are plugged into the same powerstrip, a monster power Powerbar 1100. It has indicator lights for ground status (green) and reversed wiring (not lit). That suggests the outline is good.

This is the confusing part. Everything seems like it should be OK. Could I have an applicance not working correctly and putting RF into the common ground?

The satellite pole should be grounded to the water line within 5 feet of where it comes into the house, by national code. There are other acceptable alternatives. I would try disconnecting the power strip. It isn't really doing you much good other than the convenience of having everything plugged into one spot.

delta_charlie · Mar 29, 2010

RobbinM said:
---cut--- This is the confusing part. Everything seems like it should be OK. Could I have an applicance not working correctly and putting RF into the common ground?

Hi, maybe - you could try flipping the house circuit breakers so only the TV/sound system has power and then start flipping on other stuff and see if something starts to make noise. Also, I seem to remember a long time ago the neighbours house had some type of power cable problem that caused all kinds of wield things even at my house. Good luck, let us know if you figure it out. Later, DC

wildbill129 · Mar 29, 2010

raoul5788 said:
Actually, grounding to the water line is NEC code.

Chip, I am fully aware of NEC, trust me. In the old days, water lines were always connected to ground, and always copper. Now, with PEX and PVC they don't work. You could not ground a dish to a water line at my new house, there is no copper water lines, it's all PEX.

The NEC allows grounding of dishes to water lines if the house is completely copper AND tied to the house bond. That is the only time. The preferred method is the house bond.

NEC Approved Grounding Points

There are 5 general locations where you can ground a satellite system.

1. Electrical service electrode (ground rod), or the conductor that connects the ground rod to the electrical service panel.
The ground rod must be the main electrical ground rod, or if a separate ground rod is installed, bonded to the primary ground with 6 gauge ground wire. It is a common practice among some installers to install a 5 foot ground rod and not back bond. This can lead to several problems. See part 7 for more information about installing isolated ground rods.

2. The metal electrical service panel. A Service Panel includes the meter housing, circuit breaker , or sub panel, if the sub panel is connected to the breaker panel by a rigid metal conduit. A rigid metal conduit is typically schedule 40 steel.

3. A metal electrical raceway or rigid conduit. The metal conduit or raceway that feeds power to your service meter, or runs between service panels. To ground to a conduit, a copper or galvanized steel strap is wrapped around the pipe and secured with a screw that, when tighten, pulls the clamp tight.

4. Water pipe. BUT ONLY with in five feet of the water pipes entrance to the structure and only if the water pipe is metal and in direct earth contact for at least 10 feet before entering the property. Attaching a ground wire to a water valve is NOT ACCEPTABLE and should not be accepted.

See part 7 for more information about grounding to a water pipe. Attaching a ground wire to any water pipe beyond 5 feet from where the pipe emerges from the ground is not allowed. The image to the right shows a ground wire attached to the main water service as the line exits the ground and enters the structure. The point were the water supply pipe emerges from the earth is the pipes point of entry.
5. The grounded metal structure of a building. If the buildings metal structure is grounded by one of the above means, a ground wire can be bonded to the metal structure. This is usually used with mobile homes and commercial buildings.

wildbill129 · Mar 29, 2010

RobbinM said:
wildbill129, I have one ground rod. It's right by the electric meter. The ground block for the sat is about 2 feet from the ground rod. The satellite pole is attached to the ground block along with the two coax cables.

The satellite doesn't have it's own ground.

All components are plugged into the same powerstrip, a monster power Powerbar 1100. It has indicator lights for ground status (green) and reversed wiring (not lit). That suggests the outline is good.

This is the confusing part. Everything seems like it should be OK. Could I have an applicance not working correctly and putting RF into the common ground?

You could disconnect the ground from the dish to the ground rod and see if that helps. There will still be a ground from the ground block, which is enough to disperse static electricity, that's all the ground is good for anyway.

Is your HDMI cable going directly from the HR21 to the TV or is it going through your stereo receiver?

Did you have it connected through component video before through the receiver or directly to the TV?

Where is the power inserter for the SWM LNB? Could you move it closer to the dish and away from your components?

You don't have your coax from your dish going through your Monster power strip do you?

Is the subwoofer plugged into the powerstrip along with the HR21?

raoul5788 · Mar 29, 2010

wildbill129 said:
Chip, I am fully aware of NEC, trust me. In the old days, water lines were always connected to ground, and always copper. Now, with PEX and PVC they don't work. You could not ground a dish to a water line at my new house, there is no copper water lines, it's all PEX.

The NEC allows grounding of dishes to water lines if the house is completely copper AND tied to the house bond. That is the only time. The preferred method is the house bond.

Of course if you don't have a copper pipe for your main water feed you have to use an alternative. I may be stupid, but I'm not an idiot!

RobbinM · Mar 29, 2010

wildbill129 said:
You could disconnect the ground from the dish to the ground rod and see if that helps. There will still be a ground from the ground block, which is enough to disperse static electricity, that's all the ground is good for anyway.

I tried connecting the wire from the dish post directly to the house ground rod and leave the coax ground block non-grounded. The hum was just as loud.

Is your HDMI cable going directly from the HR21 to the TV or is it going through your stereo receiver?

My HDMI cable is connected through my stereo receiver. I just bought a new HDMI upconverting A/V receiver

Did you have it connected through component video before through the receiver or directly to the TV?

Until last week, it was correctly directly to my TV via HDMI . The old receiver had an optical cable going to it.

Where is the power inserter for the SWM LNB? Could you move it closer to the dish and away from your components?

Power inserter? I only have one satellite receiver. Do I have such a thing?

You don't have your coax from your dish going through your Monster power strip do you?

I don't have the coax going through the Monster power strip. It only has one coax connection for satellite.

Is the subwoofer plugged into the powerstrip along with the HR21?

The SW is plugged into the same Monster powerstrip. FYI, I'm not able to hear any hum from the other speakers.

jdspencer · Mar 29, 2010

RobbinM said:
...
Where is the power inserter for the SWM LNB? Could you move it closer to the dish and away from your components?

Power inserter? I only have one satellite receiver. Do I have such a thing?...

I saw no reference to you having an SWM setup, so you won't have a power inserter.

Another test would be to use an extension cord to plug your SW into another outlet. Try several around the room.

wildbill129 · Mar 29, 2010

RobbinM said:
I tried connecting the wire from the dish post directly to the house ground rod and leave the coax ground block non-grounded. The hum was just as loud.

Is your HDMI cable going directly from the HR21 to the TV or is it going through your stereo receiver?

My HDMI cable is connected through my stereo receiver. I just bought a new HDMI upconverting A/V receiver

Did you have it connected through component video before through the receiver or directly to the TV?

Until last week, it was correctly directly to my TV via HDMI . The old receiver had an optical cable going to it.

Where is the power inserter for the SWM LNB? Could you move it closer to the dish and away from your components?

Power inserter? I only have one satellite receiver. Do I have such a thing?

You don't have your coax from your dish going through your Monster power strip do you?

I don't have the coax going through the Monster power strip. It only has one coax connection for satellite.

Is the subwoofer plugged into the powerstrip along with the HR21?

The SW is plugged into the same Monster powerstrip. FYI, I'm not able to hear any hum from the other speakers.

I read your title wrong, that you had a SWM LNB, so JDSpencer is right, you probably don't have a power inserter.

I am gathering from your post that you have a messenger wire coming from your dish and going to the ground block. There is a another wire running from the ground rod to the grounding block, correct? Disconnect the messenger wire from the dish, leaving the wire from the ground rod to the grounding block. There will still be a ground there, but that may eliminate the loop from the pole in the ground.

As JDSpencer said, try plugging the subwoofer into different outlets with an extension cord.

I would also try plugging your HR21 directly into a non-switched box in the back of the receiver. If that doesn't work, plug the sub in to the outlet, as long as it doesn't exceed the recommended wattage.

Some, higher end subwoofers, have a ground screw on the back. If yours does, run a length of #16 wire directly to the center screw on the wall outlet.

Ground loops are one of the hardest things to solve. You just have to keep plugging away.

RobbinM · Mar 29, 2010

I tried various plugs near and far today. Repluging both the SW and the Directv receiver. No difference.

What about a badly installed connector on the coax causing this? One of the shield wires in the wrong place? Can't that cause a hum?

raoul5788 · Mar 30, 2010

RobbinM said:
I tried various plugs near and far today. Repluging both the SW and the Directv receiver. No difference.

What about a badly installed connector on the coax causing this? One of the shield wires in the wrong place? Can't that cause a hum?

Have you tried running a ground from the dish to the water pipe, removing the one to the ground rod, like I suggested?

RobbinM · Mar 30, 2010

raoul5788 said:
Have you tried running a ground from the dish to the water pipe, removing the one to the ground rod, like I suggested?

There is no above ground water pipe with 50 feet of the dish. The main water line into the house is underground. So I'm not able to try this.

raoul5788 · Mar 30, 2010

RobbinM said:
There is no above ground water pipe with 50 feet of the dish. The main water line into the house is underground. So I'm not able to try this.

That's where I am saying it should be grounded, in the basement or crawlspace, within 5 ft of where it enters the house. It should be separate from the ground block.

HR21, grounding and SW hum

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