Mux C problem on communal aerial.
 

We have an issue with communal aerial system feeding our apartments.
Only some brands of STBs are able to receive Mux C, others are not able
to tune to it at all. Those that can tune in get a perfect picture. The
contractors who look after the system have been telling residents to
buy a better set top box when they get called out - and have been doing
so for the past 6 months at least judging by the recent emails on the
estate discussion board.

A bit about the system: The system pulls in analogue and digital from
Crystal Palace and shifts the frequencies then distributes with
satellite to about 750 outlets in 10 different buildings - and the
problem seems equally bad in each.

My DTT reception is fine (and I usually use satellite) so I have not
been involved until now, but I've had a look at the technical info
produced by my Nebula card and it tells me that the signal strength and
bit error rate of all the Mux are about equal - however the SNR of Mux
C is only 19db where the others are around 24db. Is this too low? And
is it something that the contractors should have noticed and fixed when
they first got called out 6 months ago?

Any advice on what the cause might be? Faulty launch amplifier perhaps?

--
Gareth Davis

Mux C problem on communal aerial.
 

In article .com,
wrote:
We have an issue with communal aerial system feeding our apartments.
Only some brands of STBs are able to receive Mux C, others are not able
to tune to it at all. Those that can tune in get a perfect picture. The
contractors who look after the system have been telling residents to
buy a better set top box when they get called out - and have been doing
so for the past 6 months at least judging by the recent emails on the
estate discussion board.

A bit about the system: The system pulls in analogue and digital from
Crystal Palace and shifts the frequencies then distributes with
satellite to about 750 outlets in 10 different buildings - and the
problem seems equally bad in each.

My DTT reception is fine (and I usually use satellite) so I have not
been involved until now, but I've had a look at the technical info
produced by my Nebula card and it tells me that the signal strength and
bit error rate of all the Mux are about equal - however the SNR of Mux
C is only 19db where the others are around 24db. Is this too low? And
is it something that the contractors should have noticed and fixed when
they first got called out 6 months ago?

Any advice on what the cause might be? Faulty launch amplifier perhaps?

It could be that one of the frequency shift units is creating a spurious
signal on top of Mux C. Or, it could be that some outside signal is leaking
in and falling on top of Mux C. Systems using frequency shift are complex.
Someone is going to have to look at the complete output with a spectrum
analyser and go on from there, otherwise it's trial and error and a lot of
time and money spent.

--
From KT24 - in drought-ridden Surrey

Using a RISC OS5 computer

Mux C problem on communal aerial.
 

In article .com,
writes
We have an issue with communal aerial system feeding our apartments.
Only some brands of STBs are able to receive Mux C, others are not able
to tune to it at all. Those that can tune in get a perfect picture. The
contractors who look after the system have been telling residents to
buy a better set top box when they get called out - and have been doing
so for the past 6 months at least judging by the recent emails on the
estate discussion board.

A bit about the system: The system pulls in analogue and digital from
Crystal Palace and shifts the frequencies then distributes with
satellite to about 750 outlets in 10 different buildings - and the
problem seems equally bad in each.

My DTT reception is fine (and I usually use satellite) so I have not
been involved until now, but I've had a look at the technical info
produced by my Nebula card and it tells me that the signal strength and
bit error rate of all the Mux are about equal - however the SNR of Mux
C is only 19db where the others are around 24db. Is this too low? And
is it something that the contractors should have noticed and fixed when
they first got called out 6 months ago?

Any advice on what the cause might be? Faulty launch amplifier perhaps?


Sounds like plain old incompetence.

Seems they don't know how to use a signal analyser . If one MUX is OK on
some boxes then its more than likely that some boxes are more sensitive
than other's, and owing to the digital threshold for reception this
makes sense that somewhere one MUX isn't as good as it might be.


Best to get Bill W to ride south again.. soon as;-)...
--
Tony Sayer

Mux C problem on communal aerial.
 

wrote in message
oups.com...
We have an issue with communal aerial system feeding our apartments.
Only some brands of STBs are able to receive Mux C, others are not able
to tune to it at all.

Have they rescanned for channels ? Do they know how to work the box?

Those that can tune in get a perfect picture.

So is it a case of some apartments can't receive a signal or haven't set the
box up correctly?
Has anyone with a working box taken it to the apartment of someone else that
says theirs doesn't work? And the other way around!

The
contractors who look after the system have been telling residents to
buy a better set top box when they get called out - and have been doing
so for the past 6 months at least judging by the recent emails on the
estate discussion board.

So everyone has just ignored the problem for 6months?

A bit about the system: The system pulls in analogue and digital from
Crystal Palace and shifts the frequencies then distributes with
satellite to about 750 outlets in 10 different buildings - and the
problem seems equally bad in each.


But you have said that some apartments have no trouble, so the problem can't
be bad in each. You need to establish if it is user error or the box in use
is rubbish.

My DTT reception is fine (and I usually use satellite) so I have not
been involved until now,

Why get involved now then, everyone else seems happy ignoring it.

but I've had a look at the technical info
produced by my Nebula card

That isn't a digital TV box - try getting one of the neighbours to lend you
their box that seems to refuse to work.

and it tells me that the signal strength and
bit error rate of all the Mux are about equal - however the SNR of Mux
C is only 19db where the others are around 24db. Is this too low? And
is it something that the contractors should have noticed and fixed when
they first got called out 6 months ago?


The contractor would need to test the system, if they have done and there is
no fault, they might be right in the advice they give. You know what some
people are like. Install a system and if they put the wrong videoplus code
in, they are on the phone saying your aerial installation is crap!

Any advice on what the cause might be? Faulty launch amplifier perhaps?


You need to speak to the company concerned, but I wouldn't self appoint
yourself as technical adviser as you don't seem to know much about aerial
distribution systems - and your digital box works fine! If you must appoint
yourself as a technical adviser, but really just want to relay info given on
this group, you might be better paying for another company to come in and
give advice. Have the work done if requied and sue the original company.

--
Gareth Davis

Mux C problem on communal aerial.
 

tony sayer wrote:

[stuff snipped]


Sounds like plain old incompetence.


We suspected as much, but nice to get a second opinion.

Seems they don't know how to use a signal analyser . If one MUX is OK on
some boxes then its more than likely that some boxes are more sensitive
than other's, and owing to the digital threshold for reception this
makes sense that somewhere one MUX isn't as good as it might be.


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.


Best to get Bill W to ride south again.. soon as;-)...


Having read this group for a while I do wonder if Bill is the only
decent rigger in the country sometimes, perhaps Bill should start a
franchise or run an aerial academy or something :)

--
Gareth Davis

Mux C problem on communal aerial.
 

mal wrote:
wrote in message
You need to speak to the company concerned, but I wouldn't self appoint
yourself as technical adviser as you don't seem to know much about aerial
distribution systems - and your digital box works fine! If you must appoint

I'm not in the mood to start a flame war but I'm not going to let that
pass :)
I asked the question on here because there are a number of people who
post here who know a lot more than me about SMATV systems and who's
opinions I really respect after following the newsgroup on and off for
several years after working in the technical side of radio.

If your opinion is that everything is down to user error then fine, but
the contractors did at least do a rescan on people's boxes when they
visited before telling them that their freeview box was at fault. After
someone posted their experience with the contractors on our smartgroups
forum and was followed by a chorus of 'me to' postings it became
obvious that this had been going on for months.

I can see your suggested way of dealing with the situation is don't get
involved and leave it too the experts - well the expert opinion from
the contractors does not hold water, I don't believe E3 has suddenly
been blighted by a shedload of faulty freeview boxes - which work fine
with an indoor aerial (until the signal gets wiped out by the 20KV
sparks from passing trains).

--
Gareth Davis

Mux C problem on communal aerial.
 

Mux C problem on communal aerial.
 

In article .com,
writes

tony sayer wrote:

[stuff snipped]


Sounds like plain old incompetence.


We suspected as much, but nice to get a second opinion.

Seems they don't know how to use a signal analyser . If one MUX is OK on
some boxes then its more than likely that some boxes are more sensitive
than other's, and owing to the digital threshold for reception this
makes sense that somewhere one MUX isn't as good as it might be.


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.


Best to get Bill W to ride south again.. soon as;-)...


Having read this group for a while I do wonder if Bill is the only
decent rigger in the country sometimes, perhaps Bill should start a
franchise or run an aerial academy or something :)

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.....
--
Tony Sayer

Mux C problem on communal aerial.
 

Usenet wrote:


Having read this group for a while I do wonder if Bill is the only
decent rigger in the country sometimes, perhaps Bill should start a
franchise or run an aerial academy or something :)


Well there is always me, 13 years in the industry, but I'm in Northern
Ireland. All my systems have every point tested and datalogged so if
there is a problem, it is easily resolved. Takes a bit longer to do but
well worth it.

Sorry, no disrespect intended. You do get the impression reading this
group that there are a lot of bad riggers out there. But it's the same
in any industry I guess, I work in the New Media and Internet industry
- and there are a lot of hosting companies out there that really put
the SH into IT!


Have the DTT muxes been shifted too or just the analogue to prevent
pre-echo?


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.

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.

--
Gareth Davis

Mux C problem on communal aerial.
 

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