Ha ha. You and I have a lot of practical experience. I hope our younger readers are paying attention. 
Freesat box seems to be LIVE!!!
- Thread starter mypetearthling
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Ha ha. You and I have a lot of practical experience. I hope our younger readers are paying attention.
Oh, I'm not as old as you think.
I didn't used to be old. It crept up on me. I remember being thin.
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Many years ago I went to a lecture on earthing aerials. It was interesting to say the least. He pointed out all the things we should not do like do not mount on an earthed structure soot lined chimney is out. Also not on sharp edges should not use gable end of house.
It would seem we have been getting it wrong for years but to be fair he was talking about a G5RV on 80 meters not a TV aerial. However some of the points raised are still valid.
The TV aerial is not really a problem as we can use decoupling capacitors however for a dish we need a DC supply. However unlike the Yargi we don't need to mount a dish high up and mounted on the wall unlikely it will get a lighting strike. So 10 foot off the ground can't really see a problem in earthing the dish.
However I question why the dish should make the set top box live? Should be 300mm separation or an earthed divider between the data cable (coax) and any low voltage (230vac) cables. Even if the rules were not followed the chance of getting a shock are very low.
So I would be looking for a fault. First thing I would look for is any combiner/splitter unit likely fitted in loft which may be faulty. Either it could be connecting the aerial to mains supply or connecting the dish to the terrestrial aerial without using a decoupling capacitor.
Next would be earth system in house. Not unknown for back boxes to become live and transfer that to other items.
On change of occupant or every 10 years one is suppose to have an Electrical Installation Condition Report was called a Periodic Inspection Report this should highlight any faults. I have been surprised to find quite so many cases of line - neutral swaps.
Something like this
is not as good and a proper EICR but in real terms is likely to highlight most of the faults. Note I have shown one with a loop test.
I will guess there is a major fault some where. But the chances of working out where on a forum are slim. I would recommend getting an electrician and at £42.30 plus vat for tester likely the electrician is the cheap option.
It would seem we have been getting it wrong for years but to be fair he was talking about a G5RV on 80 meters not a TV aerial. However some of the points raised are still valid.
The TV aerial is not really a problem as we can use decoupling capacitors however for a dish we need a DC supply. However unlike the Yargi we don't need to mount a dish high up and mounted on the wall unlikely it will get a lighting strike. So 10 foot off the ground can't really see a problem in earthing the dish.
However I question why the dish should make the set top box live? Should be 300mm separation or an earthed divider between the data cable (coax) and any low voltage (230vac) cables. Even if the rules were not followed the chance of getting a shock are very low.
So I would be looking for a fault. First thing I would look for is any combiner/splitter unit likely fitted in loft which may be faulty. Either it could be connecting the aerial to mains supply or connecting the dish to the terrestrial aerial without using a decoupling capacitor.
Next would be earth system in house. Not unknown for back boxes to become live and transfer that to other items.
On change of occupant or every 10 years one is suppose to have an Electrical Installation Condition Report was called a Periodic Inspection Report this should highlight any faults. I have been surprised to find quite so many cases of line - neutral swaps.
Something like this
is not as good and a proper EICR but in real terms is likely to highlight most of the faults. Note I have shown one with a loop test.I will guess there is a major fault some where. But the chances of working out where on a forum are slim. I would recommend getting an electrician and at £42.30 plus vat for tester likely the electrician is the cheap option.
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It doesn't. The box uses an SMPS with no earth connection, as such it's floating to earth. A little capacitive leakage and you get some shocks.
The lack of earth on the coax shield is what allows it to float, many places earth the shield and this never comes up.
Indeed, so much equipment these days has no earth - and for good measure it's almost universal to have two caps forming a divider between L & N with the centre point being connected to chassis. Thus you have a (weak) divider trying to hold the chassis at a steady 120V AC
If everything in the system is unearthed then the whole system will be weakly live - but if any item is earthed then that will provide an earth to the rest fo the equipment via the connecting leads (though putting a 50Hz current through the screen doesn't seen a cleaver idea).
I can't see why using a normal 13A plug to get a good earth and properly earthing all the equipment (via a case screw) is a bad idea. I don't buy the attracting lightning argument - everything (and therefore the antenna) is going to be "weakly earthed" anyway, and I can't see the lightning being affected by whether you've got something earthed or at around 120V AC or less from earth.
This thread may be of interest.
If everything in the system is unearthed then the whole system will be weakly live - but if any item is earthed then that will provide an earth to the rest fo the equipment via the connecting leads (though putting a 50Hz current through the screen doesn't seen a cleaver idea).
I can't see why using a normal 13A plug to get a good earth and properly earthing all the equipment (via a case screw) is a bad idea. I don't buy the attracting lightning argument - everything (and therefore the antenna) is going to be "weakly earthed" anyway, and I can't see the lightning being affected by whether you've got something earthed or at around 120V AC or less from earth.
This thread may be of interest.
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