TV socket charge up
On Thu, 30 Mar 2017 21:52:11 +0100, Bill Wright
On 30/03/2017 19:39, Johnny B Good wrote:
The aerial leakage path to earth can vary from as low as a hundred ohms
or so to as high as a few hundred kilo ohms depending on how the aerial
was actually installed and varies with the local weather conditions,
notably the difference between a hot sunny day after a spell of dry
weather or a day of prolonged rainfall after several such damp days.
It depends a lot on the design of the aerial. Some don't have a
connection between the coax and the supporting mast (etc) because the
dipole isn't folded and thus isn't secured at the mid-point. Also some
mast clamps have a plastic insert.
Aerials screwed to a plastic fascia can be effectively isolated from
Aerials in lofts ditto.
For aerials on chimney or wall brackets on masonry, assuming the coax is
connected to the mast, it all depends on how wet the masonry is.
However, there is such a thing as conductive mortar, I'm told.
Unless one or more of the items has an actual galvanic connection to
earth, the severity of the shock will keep increasing as you add
additional mains powered double insulated kit to the mix. The best and
simplest solution to this problem is to connect a safety earth to one of
the offending items, preferably the one into which the aerial is plugged
into. Alternatively, failing that, just remember to wear marigolds
whenever you feel the need to fiddle about with the TV aerial
Yes try climbing an aluminium ladder in the rain and then touching the
dish of a communal system that's been incorrectly installed with no
earth bond and has 30 Sky boxes connected to it.
The original Sky Digital box, the Amstrad DRX100 had its chassis
earthed via the three core mains lead.
I think there was a slim Sony box that was also earthed.
I wonder why Sky specified this for some early boxes, then embraced
the Class II paradigm thereafter?