Re: Distributing digital signals in an apartment block

In article <1127561311.869089.119690@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
spiney
<sparkistuf@xxxxxxxxxxxxx> wrote:
> Ah, SMATV earthing, replies at last, from Martin and Owen.
> Interestingly, both quote IEE regs, but almost entirely disagree (in
> fact, martin is mostly correct).

I'm sure that Martin will be greatly relieved to hear that you think he is
"mostly correct". Very generous of you. :-)

> If in doubt, then obviously, just run a separate earth path direct from
> the SMATV system to the local earth, That way, there's no ambiguity (or
> lawsuits!).

This isn't a matter of "when it doubt". It is a matter of ensuring
correct and safe earthing.

> Otherwise, I strongly object to what I've said being repeatedly
> misrepresented, in a "flame war", especially when health and safety
> issues are involved.

I have not seen anything I'd recognise as a "flame war" aimed at you on
this thread/topic. However in various threads I have seen various people
make comments to the effect that you have made inaccurate or misleading
statements. If this upsets you, then I regret that, but I think it was
reasonable for them to do so in the cases I've read.

So far as I can tell, neither I, nor anyone else on this topic has
misrepresented what you have written. Indeed, I have quoted what you wrote
when commenting in order to try and ensure this could not arise.

if you think any of the comments I have made are personal attacks or
abuse, then please quote them, and give the details of the posting, and I
will check. My recollection/belief is that I have not done this, so if you
think so, you may be misinterpreting attempts to deal with problems with
what you have *said* as being an attack on yourself. If I have been
offensive or objectionable, please give me the details, and I will be
happy to apologise if this is, indeed, the case.

BTW If you think this is a "flame war" then I fear you have lead a very
sheltered life. If you want to encounter *real* "flame wars" I can suggest
some other groups to try, and topics to bring up on them. 8-]

> The IEE regs say a water pipe is not a "reliable earth", ie, it cannot
> be assumed to be continuous, or direct to earth, or to make sufficient
> earth contact. You're not allowed to use it for a local earth, or as a
> part of mains wiring earth.

At last! This isn't the implication of what you initially wrote, so it is
a relief to see you now making a more reliable statement. :-)

The point is that you can't use water pipes as you can't assume they are
reliable.

One of your difficulties, I suspect, is that the way you use 'hotmail'
makes it hard for you to actually check and quote, so you risk
contradicting yourself, or misunderstanding the meaning of comments on
previous statements.

[snip]

> What constitutes an "acceptable earth path" is obviously open to debate.

That may be so. However it should now be clear that a water pipe *cannot*
be assumed to be an "acceptable earth path". That was the point I was
trying to clarify/establish.

Hence - to quote again to avoid misunderstanding - when you wrote:

On 20 Sep in uk.tech.digital-tv, spiney <sparkistuf@xxxxxxxxxxxxx> wrote:

[snip]

> Just one more thing, answering an above post. Earthing requirements for
> SMATV are given on the DTG website. Coax cable sheaths must carry 30A
> for 10s before melting (in casr somebody connects theirs to a
> cooker/shower circuit!). The earth connection must be at least 4 square
> millimetres x-section. Water pipe is acceptable, if connected to the
> local earth (it should be!). If landlords/utilities replace metal pipe
> sections with plastic, it's legally up to them to restore the earth,
> just a letter through doors is not acceptable! An unearthed SMATV system
> is still reasonably "safe", of course, but no longer legal!

AIUI The mistake was for you to assert that "water pipe is acceptable" as a
ground for SMATV (or other general domestic equipment purposes).

That was the point I was trying to get across to you - and was covered by
other postings by other people in this thread.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html
.

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