Installing Dishes In Spain for 2E Chit-Chat

[timo_w2s]

Just had another thought, how would You earth an offset LNB, for example a BU single?
Cut the outer plastic casing and screw an earth wire to inner components?

Well, for a single LNB it's not normally an issue as it's only going to one receiver.

The Invacom QDF-031 quad has an earthing point on the LNB case but most do not.

My parents have got an earth bond bar with f-connectors on it so that the outer shield of the coax is connected to earth on all the feeds for a dish shared with the neighbour (semi detected) that was put in when the dish was installed years ago.


However, as I'm not a qualified electrification so I have no idea if this would have helped in your situation. I understand it's there to protect the other receivers or users if one receiver develops a fault or phase differences causes high voltages.

 

[Archive4]

Well, for a single LNB it's not normally an issue as it's only going to one receiver.

The Invacom QDF-031 quad has an earthing point on the LNB case but most do not.

My parents have got an earth bond bar with f-connectors on it so that the outer shield of the coax is connected to earth on all the feeds for a dish shared with the neighbour (semi detected) that was put in when the dish was installed years ago.

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However, as I'm not a qualified electrification so I have no idea if this would have helped in your situation. I understand it's there to protect the other receivers or users if one receiver develops a fault or phase differences causes high voltages.

If the house earth check proves nothing may have to look into that option. Seems strange though, have worked on several shared dishes and never had this before.
They are also thinking of putting in a multi switch, will need to look at earthing that as well

 

[timo_w2s]

If the house earth check proves nothing may have to look into that option. Seems strange though, have worked on several shared dishes and never had this before.

I wouldn't want to make any stereotypical generalisations but maybe they are a bit more health and safety paranoid this side of Europe...? ;)

 

[archive10]

My parents have got an earth bond bar with f-connectors on it so that the outer shield of the coax is connected to earth on all the feeds for a dish shared with the neighbour (semi detected) that was put in when the dish was installed years ago.

However, as I'm not a qualified electrification so I have no idea if this would have helped in your situation. I understand it's there to protect the other receivers or users if one receiver develops a fault or phase differences causes high voltages.

The earth bond bar is required in professional installations in the States to comply with electrical codes. I think this is mainly to do with protection from lightning strikes on free-standing dishes.

However, I also seem to remember reading about the risk of a potential difference between the antenna's earth, and a house earth (through your receiver equipment) in case the antenna ground spit is too far from the house ground spit. I think the solution was to carry ground to the dish too. Or something like that.

Now, in this particular case, If you share a dish between to separate electrical installations with a potential difference (ie. difference in ground potential), you may get a potential difference in potential (never thought I'd get to write that!).

So here, it would probably be better if the cables were grounded with a bar like the one pictured and a ground spit (if free-standing). But then again, I'm no qualified electrician, so someone should ask a pro about this...

 

[Archive4]

Now, in this particular case, If you share a dish between to separate electrical installations with a potential difference (ie. difference in ground potential), you may get a potential difference in potential (never thought I'd get to write that!).

So here, it would probably be better if the cables were grounded with a bar like the one pictured and a ground spit (if free-standing). But then again, I'm no qualified electrician, so someone should ask a pro about this...

Yep, I can see the potential in this explanation!

Two slight flaws, don´t think the ground spit would look too good going through the bedroom, down to the kitchen, then into the ground below! Secondly, don´t think the approx three meter gap between the two dwellings should cause a difference between the ground potential, unless of course one isn´t grounded.

Good thinking, but I´m still back to stage one. GROUNDHOG DAY !

 

[Menorca Man]

If considering earthing the LNB then either earth it at the LNB or at the receiver but not both. This will prevent the possibility of earth loop interference being introduced into the antenna feed. In Brian's case it would be more convenient to apply an earth to the receiver's chassis if it hasn't already got one.

I wouldn't worry about a direct lightning strike on the dish as a thin earthing wire attached at either the LNB or receiver wouldn't do much to prevent it frying the LNB, aerial cable and associated receiver!!

 

[Huevos]

Are the two houses on different phases? Maybe some kind of cross-phase pulse is causing the problem?

Anything is possible here. Went to a house the other day and instead of 1 phase and neutral they had 2 phases. Had to call the electric board.

Anyway normally here if you contract more than a 5 KV/A supply you will have 3 phase.

And yes, earthing here is a nightmare. After all we live in a desert. So the only time earthing works is when there's been a recent rainstorm. Houses are supposed to have an RCD by law, but not all do.

So even if the LCD were earthed, what would it be earth to?

Anyway the worst thing about all this is that the neighbour can put 240V up the the outer of the coax... and next time the missus does the dusting she touches the satellite receiver and gets electrocuted.

 

[Huevos]

If considering earthing the LNB then either earth it at the LNB or at the receiver but not both.

The whole point of earthing/bonding is that you do it everywhere, to hold the complete system at the same potential.

 

[PaulR]

Anything is possible here. Went to a house the other day and instead of 1 phase and neutral they had 2 phases. Had to call the electric board.

Interesting! Was this a new build house or was it already inhabited? If the latter, had none of the electrical equipment objected to being force-fed 415V?

 

[Huevos]

Someone did some mods at the end of the street. The dishwasher had packed up and the satellite receiver. Nothing else affected. Don't forget, a lot of stuff these days use switch mode power supplies so wouldn't notice.

 

[PaulR]

Lightbulbs?

 

[timo_w2s]

Lightbulbs?

I would think incandescents would be very bright for a little bit.

 

[Menorca Man]

The whole point of earthing/bonding is that you do it everywhere, to hold the complete system at the same potential.

Yes and no! True when preventing the possibility of electrocution but different if you are dealing with very low voltage RF or AF signals over long cable runs. Earthing both ends of a screened cable increases the possibility of introducing electrical noise due to an earth loop. There are many articles about this phenomena on the Internet and the extract below is from Wikipedia article http://en.wikipedia.org/wiki/Ground_loop_(electricity) in which I've highlighted the conflict between the two requirements.

"The causes of ground loops have been thoroughly understood for more than half a century, and yet they are still a very common problem where multiple components are interconnected with cables. The underlying reason for this is an unavoidable conflict between the two different functions of a grounding system: reducing electronic noise and preventing electric shock. From a noise perspective it is preferable to have "single-point grounding", with the system connected to the building ground wire at only one point. National electrical codes, however, often require all AC powered components to have third-wire grounds; from a safety standpoint it is preferable to have each AC component grounded. However the multiple ground connections cause ground loops when the components are interconnected by signal cables, as shown below."

 

[PaulR]

I would think incandescents would be very bright for a little bit.

There should have been popping noises like Champagne bottles being opened all along that street!

 

[Captain Jack]

3-phase in Spain should be 380V if the mains is 220V like it is in Russia/rest of Europe.

 

[Archive4]

Gentlemen, this is all very interesting and takes me back some 30+ years to when I did my HND in Telecoms and had to suffer 3 years of EP ( Electrical Principles ) Studied all aspects of mains electrical, including 3 phase star and delta configuration. Still not helping me stop the LNB blowing up!
Being as we live in a desert I could ask the client to urinate on the earth spike once a month to ensure connection, would this help?

 

[joddle]

Gentlemen, this is all very interesting and takes me back some 30+ years to when I did my HND in Telecoms and had to suffer 3 years of EP ( Electrical Principles ) Studied all aspects of mains electrical, including 3 phase star and delta configuration. Still not helping me stop the LNB blowing up!
Being as we live in a desert I could ask the client to urinate on the earth spike once a month to ensure connection, would this help?

But are the receivers the same on the lost feed to the ones on the other feeds? - if they are not it could be that some are better than others at insulating against spikes. If they are the same then that rules out receiver issues and means something is going high in just the one house (or at least higher enough to do damage). I can only think that voltage overload would pop the LNB so something a bit more than 15v was going up the cable. I guess the spike must have been at least double the wokring voltage to do any damage as there must be a fair safety margin built into the LNB - yet the voltage was not so high it also took out the other feeds - for which I suppose a much higher pulse would be required, perhaps hundreds of volts or more! So what could cause this? - my gusess is mains fluctuation - as stated before we have had 400v pop through our wires at sometime (an exception I know) but we do get the occasional brightening of lights -possibly due to unevan loading somewhere else on the three phases in our street or close by. If this is happening on one propery and not the other then maybe pulses along with bad earthing are allowing high voltage spikes which damage the LNB but not enough to take out other kit. You also mentioned the cable to the bad feed is longer than the other house, but is it close to any electrical switchgear? - just a thought.

 

[Archive4]

But are the receivers the same on the lost feed to the ones on the other feeds? - if they are not it could be that some are better than others at insulating against spikes. If they are the same then that rules out receiver issues and means something is going high in just the one house (or at least higher enough to do damage). I can only think that voltage overload would pop the LNB so something a bit more than 15v was going up the cable. I guess the spike must have been at least double the wokring voltage to do any damage as there must be a fair safety margin built into the LNB - yet the voltage was not so high it also took out the other feeds - for which I suppose a much higher pulse would be required, perhaps hundreds of volts or more! So what could cause this? - my gusess is mains fluctuation - as stated before we have had 400v pop through our wires at sometime (an exception I know) but we do get the occasional brightening of lights -possibly due to unevan loading somewhere else on the three phases in our street or close by. If this is happening on one propery and not the other then maybe pulses along with bad earthing are allowing high voltage spikes which damage the LNB but not enough to take out other kit. You also mentioned the cable to the bad feed is longer than the other house, but is it close to any electrical switchgear? - just a thought.

NO. Possibly. Yes. Incorrect, o.2mA across the heart can kill you at the right/wrong time, o.2mA can also re-start your heart when done by a professional! See previous answer. Not sure if V or A. Good question. Get lower candle bulbs. Possibly. No

I think that answered all questions! Other than the thought, need to specify!

 

[joddle]

Yes questions answered - but still trying to make sense of your problem! And I sympathise with your frustration.

First I would
a) measure the voltage between the earths in the property - if there is a significant difference then earthing could be the root of the problem.

Two other things then I would try to see how good the mains supply is .
b) measure the voltage across the lives from each property
c) measure the voltage across the neutrals

Assuming on the same phase, then if there are any significant differences then perhaps that may explain differentials between the properties. If there are very high differences then maybe phase is the key here.

I think your observation about low currents affecting the heart may not be quite so relevent here as it takes a voltage to generate a current to breakdown a component and insulation breakdown or compenent breakdown is usually caused by exceeding a design voltage parameter.

My final measurement would be across the centre feeds to the LNB from a receiver in each of the properties to see if there is any PD between the that generated by the kit in each house arriving at the LNB. In theory they should be very similar if not exactly the same.

Maybe you have other ideas and after all you are there and can see the situation whereas I cannot - but something is causing the thing to blow and the cause must be coming from somewhere!!!

 

[Archive4]

I think your observation about low currents affecting the heart may not be quite so relevent here as it takes a voltage to generate a current to breakdown a component and insulation breakdown or compenent breakdown is usually caused by exceeding a design voltage parameter

TKS, I know we all trying to help solve the problems we encounter!
I must disagree with the low current theory though. I played with many a Van de Graaff at school and with BT, 100,000V up to 5,000,000V with no current. Made your hair stand up, but that was about all! It ain´t volts that kill you, but amps will!