On 06/11/2020 22:43, Brian Morrison wrote:
On Fri, 06 Nov 2020 20:38:46 +0000, The Natural Philosopher wrote:

On 06/11/2020 18:10, Brian Morrison wrote:
On Fri, 06 Nov 2020 15:46:20 +0000, The Natural Philosopher wrote:

A galvanic isolator is a way to prevent corrosion in boats. WTF is one
doing in a Broadband setup?

It is used to disconnect the internal equipment from the external
broadband cabinet and equipment. It also acts to prevent ground loops
via the coax cable that supplies the cable broadband signal. It might
be what everyone else calls a braid breaker.

Gosh. Ground loops. 50hz hum on a megahertz signal...Do you folks over
on uk.radio.amateur actually have *any* electronic experience *at all*.?

Quite a lot actually, professional RF engineer for 40 odd years here.
Coupling between different signals can be problematic, I assume that the
cable people have a whole variety of kit to fix these issues. Jim has had
a fairly long time with the same ISP I think, so he may have a relatively
old installation that is a bit more sensitive to the exact topology
around and inside his house. It's not easy when you are constrained in
what can be fitted, cable internet is quite after-market in nature
certainly 25 years ago when a lot of it was initially fitted.

The point is, that people who do electronics professionally, as I did
for many years, have been there, done that, got the T shirt and
automatically, simply as a way of reducing fault calls, isolated their
domestic kit that plugs into long lines, from any hard LF connection to
the ground. In ADSL it is conventional to have a ferrite balun IIRC. IN
CAR5 ethernet its all balanced mode anyway.

Look at Jims post. The term 'galvanic isolator' is misspelt for a start.
Secondly it is never used outside of a marine context where the point is
not to have boats floating in sea water 'earthed' to the earth and to
each other, to avoid *galvanic* corrosion.

It is never ever used by normal engineers to refer to not earthing
equipment for the avoidance of ground loops which are only relevant
anyway in the audio band. At RF there are a lot more weird effects that
come in, but earthing stuff doesn't normally make any difference.

So there are 3 solid hard reasons bound up with experience why Jim is in
fact talking through his arse.

1/. A 'galvanic isolator' is irrelevant outside of a marina.
2/. Ground loop seldom if ever have any effect at RF and above, which is
where cable operates.
3/. Despite their desire to make profits, manufacturers of electronic
kit in general make sure it works without the need for ancillary plug in
items.




Putting it in the 'wrong' position might cause a change in SNR, that
depends on exact details of the property and wiring.

Jim clearly upset it initially and then fixed it again.

The right position is in the bin, along with his tinfoil hat and quartz
crystal pyramid knife sharpener

Sometimes TNP I see what makes so many cam.misc regulars find you
abrasive. This is one such occasion.

Oh FFS. Intelligent lives matter. Do we have to pander to idiocy
everywhere, all the time?

If wannabe electronics engineers were just to actually learn the theory
and do some design, perhaps their little knowledge wouldn't be such a
dangerous thing.

And gold plated speaker wires, red sharpies to reduce CD distortion and
the like wouldn't be on sale.



--
How fortunate for governments that the people they administer don't think.

Adolf Hitler