On 07/11/2020 17:34, Brian Morrison wrote:
On Sat, 07 Nov 2020 10:16:37 +0000, The Natural Philosopher wrote:

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.

And generally it works. But twisted pair lines are more sensitive to
environment than coax, and are built to higher standards in general.
Especially in comparison with pre-2000 cable TV systems.


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.

I will admit that when I saw Jim's post, I did have to have a quick look
to see what he was referring to. As I said, braid breaker is the term
that is used in RF circles, and is mainly intended to avoid current
flowing on the outside of coax getting anywhere it's not wanted,
obviously the internal currents on coax matter but you rarely want the
outside current involved except in coax baluns.


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.

Have a look he

https://www.dipolnet.com/galvanic_is...hz__R48605.htm

and he

https://www.amazon.co.uk/ASH-GISX101...or-TELESTE/dp/
B019EGL97S/ref=sr_1_fkmr1_2?
dchild=1&keywords=galvanic+isolator+cable+tv&qid=1 604769468&sr=8-2-fkmr1



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.

See above. Terminology might not be to our taste, but it's what the
industry calls these things.

2/. Ground loop seldom if ever have any effect at RF and above, which is
where cable operates.

Depending on what is going on, it is possible for cable lengths to cause
notches within the desired passband if the grounding is imperfect or if
there is unintended inductance in ground paths. Cable TV is notorious for
this sort of effect.

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.


Yes, but as I said in after-market equipment there are always a few odds
and sods that need mopping up. I would love to say that you're right and
nothing is needed, but then I've seen enough cable TV cabinets with
broken doors on the streets, and what lies within is quite horrifying to
anyone with even a faint interest in tidiness. The F connector, usually
screw on, is the absolute cheapest and nastiest RF connector in existence.




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?

No, but if someone is asking about something that exists, and why it
might be problematic if disturbed, they deserve a fair hearing.


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.

Jim is against professionals having radio as a hobby, so his preference
is not to be too technical. Amateur radio is a broad church.


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

Don't hold with any of those. All nonsense as you well know.

Right. No more uk.d-i-y for me forthwith.

good man...they are a bunch of *******.....