Mux C problem on communal aerial.

In article .com,
wrote:

Mux C is on channel 34, so by the look of things it is just the
analogue which has been moved. Channels 1-5 are on 55,52,42,62 and 58.
There are no additional channels for CCTV or anything like that. Some
of the analogue is still ghosted even after shifting, apparently they
have been all over the roof and water towers and found 'Canary Wharf is
in the way' so nothing can be done about it.

memory says a relay was built for the area totally blocked by Canary Wharf,
but I may be wrong. It's getting misty back there.

What they may need to do, as was done at Broadcasting House, London, was to
use 5 separate aerials for the analogue channels thus avoiding a compromise
location for a single one. Since each channel will be using a separate
input umit, this shouldn't be very difficult to do.



To give them some credit, they have done a good job of keeping the
impulse noise from the electric trains out the system and the satellite
side of things is fine so they are doing something right.

--
From KT24 - in drought-ridden Surrey

Using a RISC OS5 computer

wrote:
tony sayer wrote:


No one has ever mentioned a signal analyser being used in their
apartment. The usual drill from the contractors is wiggle STB
connectors, rescan channels, tell them to buy a new box.

Nope.. You can't service large communal systems these days with DTV
signals and frequency conversion without some means of measuring and
seeing what's going on. On analogue the receiver screen will tell you
quite a bit, but digital signals need something else and the knowledge
of how to use and interpret that.


Thanks for that, very useful to know.

Yes quite.. Sorry to say that that competent aerial riggers are very few
and far between, and I'd seriously recommend that you get someone in who
knows how to service and fault find on these systems.....

And on that note: Does anyone have experience working with installers
referred through Sky Homes? Are they any better/worse than the average
CAI approved installer in Yellow Pages?

--
Gareth Davis


Don't depend on Sky Homes being an endorsement of quality.

Look for a CAI installer that is SMATV approved. The course they have to
do is quite good.

Regards
Glenn...

"charles" wrote in message
...
In article .com,
wrote:

Mux C is on channel 34, so by the look of things it is just the
analogue which has been moved. Channels 1-5 are on 55,52,42,62 and 58.
There are no additional channels for CCTV or anything like that. Some
of the analogue is still ghosted even after shifting, apparently they
have been all over the roof and water towers and found 'Canary Wharf is
in the way' so nothing can be done about it.

memory says a relay was built for the area totally blocked by Canary
Wharf,
but I may be wrong. It's getting misty back there.

A four channel relay was built in Poplar to cover the shadow of Canary
Wharf. A friend who lives there and was fed up with the lack of choice
installed a Sony DTT box against the advice of every official source and
found it works well on all but one Mux - so he still hasn't got 'five'.
Probably he doesn't care. ;-)
--
Malcolm

"charles" wrote in message
...
In article .com,
wrote:

Mux C is on channel 34, so by the look of things it is just the
analogue which has been moved. Channels 1-5 are on 55,52,42,62 and 58.
There are no additional channels for CCTV or anything like that. Some
of the analogue is still ghosted even after shifting, apparently they
have been all over the roof and water towers and found 'Canary Wharf is
in the way' so nothing can be done about it.

memory says a relay was built for the area totally blocked by Canary
Wharf,
but I may be wrong. It's getting misty back there.

Yes, it is in Poplar, on top of a residential tower block. I do not know
its name, but it is the brown one! However, it is on a very low output
power rating (around 100W, I think) and vertically polarised, unlike CP
which is horizontal.


What they may need to do, as was done at Broadcasting House, London, was
to
use 5 separate aerials for the analogue channels thus avoiding a
compromise
location for a single one. Since each channel will be using a separate
input umit, this shouldn't be very difficult to do.

Much more expensive.


--
MESSAGE ENDS.
John Porcella

John Porcella wrote:
memory says a relay was built for the area totally blocked by Canary
Wharf,
but I may be wrong. It's getting misty back there.

Yes, it is in Poplar, on top of a residential tower block. I do not know
its name, but it is the brown one! However, it is on a very low output
power rating (around 100W, I think) and vertically polarised, unlike CP
which is horizontal.

Balfron Tower

http://tx.mb21.co.uk/gallery/poplar.asp

In article ,
John Porcella wrote:


Yes, it is in Poplar, on top of a residential tower block. I do not know
its name, but it is the brown one! However, it is on a very low output
power rating (around 100W, I think) and vertically polarised, unlike CP
which is horizontal.

Yes, it has a low output becaseu it covers a small defined area. What's
wrong with VP? More transmitters use VP than HP.


What they may need to do, as was done at Broadcasting House, London,
was to use 5 separate aerials for the analogue channels thus avoiding a
compromise location for a single one. Since each channel will be using
a separate input umit, this shouldn't be very difficult to do.

Much more expensive.

I would agree it wll cost more, the price of 4 more aerials, but when
considered as part of a large wired system, it should only be a very small
increase. If it results in decent pictures, it might well be worth
spending the extra money.

--
From KT24 - in drought-ridden Surrey

Using a RISC OS5 computer

"charles" wrote in message
...
In article .com,
wrote:

What they may need to do, as was done at Broadcasting House, London, was
to
use 5 separate aerials for the analogue channels thus avoiding a
compromise
location for a single one. Since each channel will be using a separate
input umit, this shouldn't be very difficult to do.

I had a terrible problem with analogue reception on Gt Tichfield St just
behind BH (the CBC building) but DTT was perfect.

Bill

I suppose the installers need to find out if the c/n ratio is deficient at
the aerial. If so, why? Most co-channel or other problems cab be solved,
especially on such a large system where the budget will stand it. The fact
that channel conversion is used for analugue suggests that the field
strength is good.

The next move would be to find out if the c/n ratio is degraded at the
head-end. This can happen quite easily if the amplifier(s) are working too
hard. Broadband amplifiers will suffer cross-modulation which might not be
obvious on the analogue channels, and even if each mux and analogue channel
is processed separately the same thing can happen if the maximum safe output
is exceeded.

It is possible for one mux to suffer due to a response notch within its
bandwidth, caused by something as simple as a kink in the main aerial cable.
This is easy to find with an analyser. Similar notches occur as a result of
reinforcement/cancellation effects caused by shallow angle signal
reflections, for instance from water or the sides of large buildings very
near to the signal path.

If the head-end O/P is OK each repeater should be similarly tested.

Finally, the signal levels at the receivers must be adequate.

A good system, even if it uses 100dB of amplification from end to end,
should only degrade BER andf c/n marginally.

Funnily enough I've been working in London over the holiday period. The only
technical problem was caused by the VHF FM pirates, who seem to have no
regard whatsoever for other people. There was one so close to R4 that a
cheap radio could not separate the signals.

Incidentally, it was with sadistic joy that I that sailed north yesterday
along almost empty carriageways, looking at the solid bank holiday traffic
heading back to the grim south.

Bill

wrote in message
oups.com...
And on that note: Does anyone have experience working with installers
referred through Sky Homes? Are they any better/worse than the average
CAI approved installer in Yellow Pages?

That's a question with a low benchmark if ever I heard one.

Bill

wrote in message
ups.com...

By the way, do you just have one system serving all ten buildings? How long
has the system/systems been installed?

Bill