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Default Any RF experts about?

I've just been fitting TV aerials in two new houses - one a relative and
the other their new neighbour who saw what I was up to and wanted theirs
done too, for a few beer tokens..

Both jobs took longer than expected. The first was because the darling
builders had managed to get both the coax downleads to have whiskers of
braid wrapped round the core in the fitted TV/FM/SAT1+2/Return/Phone
socket in the living room. (This is quite nice, incidentally - two
downleads feed Sat2 and triplexed Sat1/TV/FM to 2x F connectors and two
UHF sockets on the twin faceplate, then a return lead takes your Sky+/
Cable/PVR UHF output back up to a bedroiom socket).

The second time, I was ready for the braid to be all over the place and
sorted that out first. Then I tried every combination going (on my own,
up and loft-ground floor in a 3 storey house loads of times) but
nothing I tried got a good signal. With my dying gasp I suspected whoever
wired it up was even worse than before and tried the 'return' cable, just
on the off chance. That was it.

Anyway, on to the point of the post ;-)

While looking for possible failure points, I checked out the (new) aerial
closely. The only electrical connections were to two alloy 'horns' near
the back which I guess the signal is focussed onto. Or rather, the
connections were to a small PCB inside the plastic box the horns came out
of. The horns were supposedly attached to the core of the coax by having
the PCB screwed down onto them - however the large contact pads that
would have touched them was still solidly covered in the non-conductive
varnish, and the screws went through the non-plated holes without joining
the two together electrically.

I measured to be sure - yup, no continuity. So I scraped some of the
varnish off and got a 1 ohm connection.

The question (finally) is this: was it designed to pass the energy by RF
coupling? Isn't that a bit lossy on what is a weak signal anyway?

And have I ballsed it up by connecting it electrically? I guess it could
have been some sort of lightning protection, but I can't see it being all
that effective, and it's in a loft now anyway...


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Default Any RF experts about?

PCPaul wrote:
I've just been fitting TV aerials in two new houses - one a relative and
the other their new neighbour who saw what I was up to and wanted theirs
done too, for a few beer tokens..

Both jobs took longer than expected. The first was because the darling
builders had managed to get both the coax downleads to have whiskers of
braid wrapped round the core in the fitted TV/FM/SAT1+2/Return/Phone
socket in the living room. (This is quite nice, incidentally - two
downleads feed Sat2 and triplexed Sat1/TV/FM to 2x F connectors and two
UHF sockets on the twin faceplate, then a return lead takes your Sky+/
Cable/PVR UHF output back up to a bedroiom socket).

The second time, I was ready for the braid to be all over the place and
sorted that out first. Then I tried every combination going (on my own,
up and loft-ground floor in a 3 storey house loads of times) but
nothing I tried got a good signal. With my dying gasp I suspected whoever
wired it up was even worse than before and tried the 'return' cable, just
on the off chance. That was it.

Anyway, on to the point of the post ;-)

While looking for possible failure points, I checked out the (new) aerial
closely. The only electrical connections were to two alloy 'horns' near
the back which I guess the signal is focussed onto. Or rather, the
connections were to a small PCB inside the plastic box the horns came out
of. The horns were supposedly attached to the core of the coax by having
the PCB screwed down onto them - however the large contact pads that
would have touched them was still solidly covered in the non-conductive
varnish, and the screws went through the non-plated holes without joining
the two together electrically.

I measured to be sure - yup, no continuity. So I scraped some of the
varnish off and got a 1 ohm connection.

The question (finally) is this: was it designed to pass the energy by RF
coupling? Isn't that a bit lossy on what is a weak signal anyway?

And have I ballsed it up by connecting it electrically? I guess it could
have been some sort of lightning protection, but I can't see it being all
that effective, and it's in a loft now anyway...



x-posted to uk.tech.digital-tv. Some aerial people there.

Andy
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Default Any RF experts about?



"Andy Champ" wrote in message
news
PCPaul wrote:
I've just been fitting TV aerials in two new houses - one a relative and
the other their new neighbour who saw what I was up to and wanted theirs
done too, for a few beer tokens..

Both jobs took longer than expected. The first was because the darling
builders had managed to get both the coax downleads to have whiskers of
braid wrapped round the core in the fitted TV/FM/SAT1+2/Return/Phone
socket in the living room. (This is quite nice, incidentally - two
downleads feed Sat2 and triplexed Sat1/TV/FM to 2x F connectors and two
UHF sockets on the twin faceplate, then a return lead takes your Sky+/
Cable/PVR UHF output back up to a bedroiom socket).

The second time, I was ready for the braid to be all over the place and
sorted that out first. Then I tried every combination going (on my own,
up and loft-ground floor in a 3 storey house loads of times) but
nothing I tried got a good signal. With my dying gasp I suspected whoever
wired it up was even worse than before and tried the 'return' cable, just
on the off chance. That was it.

Anyway, on to the point of the post ;-)

While looking for possible failure points, I checked out the (new) aerial
closely. The only electrical connections were to two alloy 'horns' near
the back which I guess the signal is focussed onto. Or rather, the
connections were to a small PCB inside the plastic box the horns came out
of. The horns were supposedly attached to the core of the coax by having
the PCB screwed down onto them - however the large contact pads that
would have touched them was still solidly covered in the non-conductive
varnish, and the screws went through the non-plated holes without joining
the two together electrically.

I measured to be sure - yup, no continuity. So I scraped some of the
varnish off and got a 1 ohm connection.

The question (finally) is this: was it designed to pass the energy by RF
coupling? Isn't that a bit lossy on what is a weak signal anyway?

And have I ballsed it up by connecting it electrically? I guess it could
have been some sort of lightning protection, but I can't see it being all
that effective, and it's in a loft now anyway...



x-posted to uk.tech.digital-tv. Some aerial people there.

Andy

It probably would have worked reasonably OK with just the capacitive
coupling through the varnish, but this won't be a design feature so you
were right to scrape it off and get a solid DC contact.

On a similar note, yesterday I re-lamped the display cabinets in
the lounge, and I appeared to have a fault with one of the fittings,
then I realised the new filament strip-light has a varnish or flux
deposit on the solder contacts that needed scraping off.
I also have seen the same thing on high wattage flood-light
lamps.

--
Graham.

%Profound_observation%


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Default Any RF experts about?

PCPaul wrote on 30/04/2009 :
I measured to be sure - yup, no continuity. So I scraped some of the
varnish off and got a 1 ohm connection.

The question (finally) is this: was it designed to pass the energy by RF
coupling? Isn't that a bit lossy on what is a weak signal anyway?

And have I ballsed it up by connecting it electrically? I guess it could
have been some sort of lightning protection, but I can't see it being all
that effective, and it's in a loft now anyway...


The signal will capacitively couple it through the insulation, but you
will get a slightly better signal with the insulation scraped away.
What you are looking at is a folded dipole, if it forms a flattened
loop.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk


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Default Any RF experts about?

The question (finally) is this: was it designed to pass the energy by RF
coupling? Isn't that a bit lossy on what is a weak signal anyway?

And have I ballsed it up by connecting it electrically? I guess it could
have been some sort of lightning protection, but I can't see it being all
that effective, and it's in a loft now anyway...


What make was it?. Wouldn't have been lightning protection anything like
that is akin to ****ing on a nuclear explosion let alone a house
fire;!...
--
Tony Sayer



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"Andy Champ" wrote in message
news
Both jobs took longer than expected. The first was because the darling
builders had managed to get both the coax downleads to have whiskers of
braid wrapped round the core in the fitted TV/FM/SAT1+2/Return/Phone
socket in the living room.

Obviously. They always do.


The second time, I was ready for the braid to be all over the place and
sorted that out first. Then I tried every combination going (on my own,
up and loft-ground floor in a 3 storey house loads of times) but
nothing I tried got a good signal. With my dying gasp I suspected whoever
wired it up was even worse than before and tried the 'return' cable, just
on the off chance. That was it.

They do this half the time, because it's a 50/50 chance. You just get used
to it. We work on the assumption that everything will be wrong. This is
usually justified.

Some years ago we did a job where the wallplate was incorporated into a
fancy 'media plate' which incorporated mains, phone, and TV. These plates
were a nightmare to remove and a double nightmare to refit. It was part of
the sparks' job to do the aerial/satellite cables. When I went round testing
the first one was wired the wrong way round, so I took it off the wall,
corrected it, and put it back. This took about 20 minutes! The next one was
OK but the next one wasn't. So I put a piece of black tape on it as a marker
and moved on. Finally I emailed the sparks to tell them to swap round the
cables to about thirty plates. This they agreed to do. But when people
started to move in we got a call from someone saying 'no telly' so I went
out and sure enough the cables were still the wrong way round. So I passed
it back to the sparks, and all further calls to that development were
refused until they had been out and tried swapping the cables round.

On the same job we had strongly advised the fitting of two sat feeds to each
dwelling, but the builder wouldn't pay the extra few quid. Even now we get
calls from there about Sky+.


While looking for possible failure points, I checked out the (new) aerial
closely. The only electrical connections were to two alloy 'horns' near
the back which I guess the signal is focussed onto. Or rather, the
connections were to a small PCB inside the plastic box the horns came out
of. The horns were supposedly attached to the core of the coax by having
the PCB screwed down onto them - however the large contact pads that
would have touched them was still solidly covered in the non-conductive
varnish, and the screws went through the non-plated holes without joining
the two together electrically.


The mention of 'horns' makes me visualise a DIY or European 'high gain'
aerial which will undoubtedly be wideband.


I measured to be sure - yup, no continuity. So I scraped some of the
varnish off and got a 1 ohm connection.

The question (finally) is this: was it designed to pass the energy by RF
coupling?

No, it's just a **** design.

Isn't that a bit lossy on what is a weak signal anyway?

Doubt it really.


And have I ballsed it up by connecting it electrically?

No.

I guess it could
have been some sort of lightning protection, but I can't see it being all
that effective, and it's in a loft now anyway...

No, deffo not lightning protection.


x-posted to uk.tech.digital-tv. Some aerial people there.

The actual real world beating aerial experts live there actually.

Bill


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"tony sayer" wrote in message
...
The question (finally) is this: was it designed to pass the energy by
RF
coupling? Isn't that a bit lossy on what is a weak signal anyway?

And have I ballsed it up by connecting it electrically? I guess it
could
have been some sort of lightning protection, but I can't see it being
all
that effective, and it's in a loft now anyway...


What make was it?. Wouldn't have been lightning protection anything like
that is akin to ****ing on a nuclear explosion let alone a house
fire;!...
--
Tony Sayer


So half a mil of varnish is going impede a lightning bolt that can travel
through thousands of meters of air (quite a good insulator - look at all
those 440kV grid cables).


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In article , R. Mark Clayton
scribeth thus

"tony sayer" wrote in message
...
The question (finally) is this: was it designed to pass the energy by
RF
coupling? Isn't that a bit lossy on what is a weak signal anyway?

And have I ballsed it up by connecting it electrically? I guess it
could
have been some sort of lightning protection, but I can't see it being
all
that effective, and it's in a loft now anyway...


What make was it?. Wouldn't have been lightning protection anything like
that is akin to ****ing on a nuclear explosion let alone a house
fire;!...
--
Tony Sayer


So half a mil of varnish is going impede a lightning bolt that can travel
through thousands of meters of air (quite a good insulator - look at all
those 440kV grid cables).



400 kV so I'm told .

Or read..


http://www.edfenergy.com/products-se...N_network_area
_132_EHV_NG.pdf
--
Tony Sayer



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On Fri, 1 May 2009 10:47:20 +0100 someone who may be tony sayer
wrote this:-

those 440kV grid cables).


400 kV so I'm told .


Between phases, in the UK.

440kV is a voltage used elsewhere though.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54
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In article ,
David Hansen wrote:
On Fri, 1 May 2009 10:47:20 +0100 someone who may be tony sayer
wrote this:-


those 440kV grid cables).


400 kV so I'm told .


Between phases, in the UK.


440kV is a voltage used elsewhere though.


It's odd, because upto the time of the supergrid all distribution voltages
in the UK were divisible by 11. (440v, 11kV, 33kV, 132kV, 275kV)

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11



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In article , David Hansen
scribeth thus
On Fri, 1 May 2009 10:47:20 +0100 someone who may be tony sayer
wrote this:-

those 440kV grid cables).


400 kV so I'm told .


Between phases, in the UK.

440kV is a voltage used elsewhere though.




They use a lot of different voltages elsewhere .. up to 900 kV DC
somewhere IIRC...

--
Tony Sayer

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