Help Required Multiswitches and earthing/grounding.

I

intracube

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Hi,

I'm looking at the EMP Centauri multiswitches (eg MS17/12PIU-6 V10).

The last page of the manual says:
"Due to security reasons the product and wiring in which the product is connected, must be grounded properly. Use the terminal identified with the appropriate symbol to ground the product. Make sure the antennas are grounded properly."
http://www.emp-centauri.cz/pdf/1003021.pdf

Is this likely for earth bonding when distributing to multiple properties or some other reason?

Is it something that can be left unconnected for single-house setups?
 
A

archive10

Guest
No, this goes for single dwelling installations too.
You should always make sure the signal-carrying equipment is earthed/grounded.
This not only alleviates ground hum, but also removes any DC offsets induced by different power phases/circuits at different points in the chain.
But it's not imperative. It will work without, and probably very wlll.
But if you can connect the ground terminal to a *real* ground (not one in an electrical socket), you should do so.
 
A

archive10

Guest
No, this goes for single dwelling installations too.
You should always make sure the signal-carrying equipment is earthed/grounded.
This not only alleviates ground hum, but also removes any DC offsets induced by different power phases/circuits at different points in the chain.
But it's not imperative. It will work without, and probably very wlll.
But if you can connect the ground terminal to a *real* ground (not one in an electrical socket), you should do so.
You can see my installation of a multiswitch here My regional Sat-CATV head-end
As you will se, the picture was taken *before* the switch was connected to the ground-wire-loop (yelow/green striped) that the other elements are connected to...
 
Terryl

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I like to use a true Earth ground as some house hold electrical service grounds can get quite noisy.

A true Earth ground would be a ground rod driven into the Earth about 6 to 8 feet as close as you can get to the equipment being grounded, or an outside metal cold water pipe.

All antennas, switches and ground blocks should be run to this ground using at least a #10 to #12 gauge copper wire with a green jacket.

All this varies between locations so check with some local electricians if not certain.
 
I

intracube

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Thanks for the replies.

I was planning to install the switch in the loft, so getting a true ground there will be a bit of work.

There's a copper cold water pipe up there, but I think its tied in to the house earth. So that's possibly not ideal.

Time permitting, I'll look in to a dedicated ground rod.
 
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In my opinion attaching your earth wire to the copper water pipe if it is connected to a pipe which is earthed will be fine for a domestic system, even with a commercial system in the UK for an apartment block, it is earthed to the main board in the landlord's cupboard. In fact for domestic use, although not ideal, it is permitted for an earth to be taken from a twin and earth in the loft if all else is impossible, that should be sufficient to guard against touch current build up from multiple devices.
 
satelliteman

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Equipotential bonding would be fine here.
 
Terryl

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A true ground is the best way, the old copper pipe may or may not still be connected to an Earth ground.

If you have no way to run a wire to the ground point then you should check the pipe out for continuity to the ground point.

I just stick a copper #12 (or #10) out a roof vent screen, then bond it to the satellite dish ground with a split bolt.

And you should use one ground only, several different ground points can cause problems.

I usually start at the dish it's self with a #10 run the shortest way directly to the ground and use a ground rod, all other equipment involved with the satellite installation outside the building is bonded to this ground, the last thing is to use a ground block right where the coax enters the building, and its bonded to the dish ground.

The ground point could also be right where the coax first enters the building, this would make the ground block the shortest ground wire, and you want to keep them as short as possible.

Also if you are in a lightning prone area a gas discharge device should be used to protect the center conductor, this can be used instead of a ground block as it will do the same job except it will provide better protection.

If the location of the dish is in the back of the house and the electrical service ground is in the front then the ground wire for the dish would be too long and could cause problems, the shorter the grond wire on an RF system the better.

You could use a #12 copper wire but if the ground wire is over 10 meters then you need to go to the next size larger,(#10 or #8) the bigger you go the better.

On my antennas here at home I have several satellite dishes, several Ham Antennas, scanner antennas and TV antennas, all tied to one ground point, and I also have a poor ground conductivity as there is rock about 10 inches down, so I used a 6 point radial ground system, with all equipment bonded to this, the main ground wire is a #2 copper.


Opps sorry...Tooo much coffee this morning, I will stop.,
 
A

archive10

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Opps sorry...Tooo much coffee this morning, I will stop.,
Nono, keep going - this is most informative.
This stuff is often overlooked in the pursuit of reception Nirvana with "what LNB" and "which dish".
 
Terryl

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The first step is "Where am I going to mount this stuff???"
 
Terryl

Terryl

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Things to watch out for, one, just wrapping a copper wire around a steel screw or bolt as a ground will cause problems later as the wire reacts to the steel and corrodes to a useless point.

What I use is a crimp/solder lug, the better ones are gold plated to prevent corrosion, and sliver plumbing solder is used to keep the galvanic action down to a minimum, this is attached to a bolt on the dish pan it's self, then run down with the coax to any switch used, the switch is bonded with a #12 gauge copper wire to the main ground wire with a split bolt*, or several wraps around the main wire and bonded with the silver solder, then run down to your ground point.

At this location the ground block (if a switch is used you don't need the ground block as the metal case of the switch will do the same) is bonded to the main ground wire.

In my opinion a ground rod is the best bet, if it's not possible to use one then the next one would be the metal cold water pipe, (DO NOT USE A GAS PIPE) and lastly the house electrical service ground.

Now in some areas if you have someone install this they have to use the house ground, you as a home owner do not have to do this unless your needing an inspection for some reason.

The reason I do not like the house ground for RF systems is the ground noise on that, every device that plugs into an AC socket makes some sort of RF noise when it turns on and off or runs, this all adds up, especially in a large town or city.

*Split bolt.....
 
I

intracube

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Thanks for the extra info folks :)

As st1 said, too often the focus is on magic 0.1dB LNBs and not so much on good cabling practices.

In the short term I'll probably opt for a connection off the cold water (after checking the earthing is all good).

It wouldn't be too much extra work to get a dedicated stake and run a cable up the side of the house. I already have to route a set of coax cables the same way.

It might also be interesting to do a comparison with my digital scope on the cold water pipe earth vs a dedicated point and see if the noise characteristics are noticeably different.
 
Terryl

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My Satellite Setup
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And now a 10 foot "C" band dish.

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I would use a 20 KHz to 3 GHz frequency RF spectrum analyzer with at least a 120 dB noise floor.
 
Channel Hopper

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An oscilloscope, so you can check mains hum.
 
I

intracube

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I would use a 20 KHz to 3 GHz frequency RF spectrum analyzer with at least a 120 dB noise floor.
My budget won't stretch that far! I'll make do with my Rigol 50MHz scope.
 
I

intracube

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Messages
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My Satellite Setup
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My Location
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You can see my installation of a multiswitch here My regional Sat-CATV head-end
As you will se, the picture was taken *before* the switch was connected to the ground-wire-loop (yelow/green striped) that the other elements are connected to...
What type of f terminators have you got for the unused outputs on the switch?

I've read conflicting info on which to use, with people saying that using 'DC blocking' type on outputs with DC will cause a short and possibly damage. But since the switch outputs (shouldn't?) have any DC, I'm thinking it should be OK?

On the other hand, terminating the switch LNB inputs could cause a problem - since there will likely be DC on them. But the EMP manual doesn't say to terminate these.

The manual also has a picture of what looks like the non DC blocking smaller variety (pg2):
https://www.emp-centauri.cz/pdf/P142-UP-P147-UP_users_manual.pdf
^ but only two are supplied for 'impedance adjustment'

Then some people say there's no need to terminate unused ports on the EMP switches at all :)
 
Terryl

Terryl

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My Satellite Setup
OpenBox X5 on a 1 meter motorized dish.
And now a 10 foot "C" band dish.

Custom built PC
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Deep in the Boonies in the central Sierra Nevada mountains of California.
I just use the screw on terminations but break off the center pins,(if termination is not needed) if used outside without a protective cover I use some dielectric grease to seal them to keep water out, this will cap them off.

Some come with little plastic caps on the ports, use them to keep the weather out.

Another way to do this is to use a weatherproof coax connector (without the coax in it) with the end sealed with hot glue.

If not specified to be used for the brand of switch your using then don't use a 75 ohm terminator cap.
 
I

intracube

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The switch will be mounted in the loft. I usually wrap amalgamating tape around any unused LNB outputs and pinch the end to seal, which seems to work well.

I linked to the wrong manual earlier. Here's the right one:
http://www.emp-centauri.cz/pdf/1003021.pdf
"If some of outputs are not used, it is appropriate to terminate them with 75 Ohm loads. If not terminated, insertion loss curve in terrestrial band may be rippled"
Though it still doesn't make it clear whether they should be DC blocked or not.
 
A

archive10

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What type of f terminators have you got for the unused outputs on the switch?
Then some people say there's no need to terminate unused ports on the EMP switches at all :)
I'm using 75 Ohm terminators for the very reasons you state.
EMP recommends it, the cabling guys at work recommend it, and I recommend it from an eletrical circuit perspective.
Unless you have specific electrical circuits that auto-terminates the connectors (and EMP doesn't), then you will be better off terminating the unused outputs.
It will probably still work without - but best performance from terminated outputs.
Never mind the DC blocking. Makes no difference; it's the same circuit all it it.
 
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