Digital TV for Residential Care Homes
 

"Woody" wrote in message
...
"Steve Terry" wrote in message
...
"Paul D.Smith" wrote in message
...
...snip...
snip
Don't forget to mention the radio stations too. Often overlooked but
you never know how many residents might welcome the chance to listen to
"Around the Horn" again.
Paul DS.

BBC7 my favourite radio channel

Around the Horn.
Bona!

Steve Terry



Sorry Steve, Round the Horn - no A in it!

And what about ISIRTA, Navy Lark, etc etc.

They don't make 'em like that any more!


--
Woody

harrogate three at ntlworld dot com


Sorry, but my Pedant nature kicked in..

It's Round The Horne (note the 'e' at the end..)

The Horne bit comes from Kenneth Horne, one of the shows stars...

Mat (With my friend Ramsden Gnomefumbler... )

Digital TV for Residential Care Homes
 

"Mat C" wrote in message
...


"Woody" wrote in message
...
"Steve Terry" wrote in message
...
"Paul D.Smith" wrote in message
...
...snip...
snip
Don't forget to mention the radio stations too. Often overlooked
but you never know how many residents might welcome the chance to
listen to
"Around the Horn" again.
Paul DS.

BBC7 my favourite radio channel

Around the Horn.
Bona!

Steve Terry



Sorry Steve, Round the Horn - no A in it!

And what about ISIRTA, Navy Lark, etc etc.

They don't make 'em like that any more!


--
Woody

harrogate three at ntlworld dot com


Sorry, but my Pedant nature kicked in..

It's Round The Horne (note the 'e' at the end..)

The Horne bit comes from Kenneth Horne, one of the shows stars...

Mat (With my friend Ramsden Gnomefumbler... )






Don't mind being a pedant, I knew it but that was a typo!


--
Woody

harrogate three at ntlworld dot com

Digital TV for Residential Care Homes
 

Dave Plowman (News) wrote:
In article ,
charles wrote:
In the majority of the London area, assuming your communal aerial works ok
for analogue it will work ok for FreeView. So only the sets themselves
will have to be changed.

I'd disagree with that statement for 2 possible reasons.
1. The distribution system might have channel pass filters.

In the majority of the London area the FreeView channels would lie within
those pass filters.

2. The system might be using 'translated' channels .

I'd think that unlikely in most care homes. Or not in any of the ones I've
visited. Low cost is usually the aim.

neither of these types of system would carry digital signals.

Of course the obvious thing is to try a FreeView tuner first before
deciding to spend what is likely to be a large amount of money.


What about using a passive system, put up a big aerial. You need about
60dBuV digital channel level to feed 64 TV IMO. Don't have to worry
about filters or amplifiers, the result will be a very low noise signal.

STBs and coax are the main expense.
--
Tony

Digital TV for Residential Care Homes
 

"Tony" wrote in message ...
What about using a passive system, put up a big aerial. You need about
60dBuV digital channel level to feed 64 TV IMO. Don't have to worry about
filters or amplifiers, the result will be a very low noise signal.

STBs and coax are the main expense.

Putting up a big aerial has an almost negligible effect on how many times
you can split the signal. But anyway, let's consider your proposition.
0dBmV from the aerial
-2dBmV in the loft
-26dBmV after the 24dB splitter loss
-30dBmV after the downlead loss (that's optimistic unless the flats are only
about a yard wide)
-32dBmV after the outlet and flylead loss.

It ain't gonna work is it?

However, if you were within about five miles of a high powered Tx and if
analogue wasn't to be used (pre-echo issue) then you'd just about get away
with it. It wouldn't be wise though. All it would need would be a dodgy
flylead or a deaf box and you'd get a call out.

In principle though, a star system with all downleads running to a central
point has a lot of advantages. Minimal amplification for a start.

Bill

Digital TV for Residential Care Homes
 

Bill Wright wrote:
"Tony" wrote in message ...
What about using a passive system, put up a big aerial. You need about
60dBuV digital channel level to feed 64 TV IMO. Don't have to worry about
filters or amplifiers, the result will be a very low noise signal.

STBs and coax are the main expense.

Putting up a big aerial has an almost negligible effect on how many times
you can split the signal.

Bill I know who you are, and that you are a knowledgable guy, but this
goes against RF theory, how can you back this up? When I say big aeial
I mean one with more gain.

But anyway, let's consider your proposition.
0dBmV from the aerial
-2dBmV in the loft
-26dBmV after the 24dB splitter loss
-30dBmV after the downlead loss (that's optimistic unless the flats are only
about a yard wide)
-32dBmV after the outlet and flylead loss.


True I did conviently forget some of the losses, especially the coax
losses. I'd revise my figure to 70-80dbuV required at the aerial.

I'm not sure what figures you're working in but -32dBm will easily drive
loads of TVs. A DTV reciever needs about 28dBuV (-80dBm ish) of mux
to get a good picture, more for a stable picture/weather etc (as long as
any adjancent analogue is proportional)

It ain't gonna work is it?

Why not? It does, I have designed several setups for test in labs and
factories for companies I have worked for. All passive distrbution its
all about the level you start with.

However, if you were within about five miles of a high powered Tx and if
analogue wasn't to be used (pre-echo issue) then you'd just about get away
with it. It wouldn't be wise though. All it would need would be a dodgy
flylead or a deaf box and you'd get a call out.


I of course realise it won't work if there isn't enough signal but many
of these places are near transmitters.

I am 10 miles from Divis, looking through a big bunch of Laylandii and
getting about 65-70dBuV at the TV after a 4 split and downlead. I can
dial in 40dB of attentuation before my STB falls over. I am using
43element from Maplin, when normally I can get all DTV (just) on a
settop aerial with direct line of site (up the hill a little). I got a
bit more than I intended actually, but also for STB test purposes.

What are pre-echo issues? I don't see how using a higher gain aerial
can cause any problems atall after you have attentuated/split the
signal. Do higher gains aerial exhibit more echo in the signal? I do
tend to think of digital only these days, we're pretty close to switch off.

In principle though, a star system with all downleads running to a central
point has a lot of advantages. Minimal amplification for a start.


I would describe my system as a tree, but how you split it doesn't
matter. I would have thought placing the 2ndary splitters around the
building will allow less coax than a star. But then I also don't
understand why ethernet networks are built like stars aswell, when local
hubs would significantly reduce the amount of cabling required and do
not reduce bandwidth. Is there some inherant benefit in reliability by
using a star?

--
Tony

Digital TV for Residential Care Homes
 

"Tony" wrote in message ...
Bill Wright wrote:
Putting up a big aerial has an almost negligible effect on how many times
you can split the signal.

Bill I know who you are,
Hell! And you know where I am!

and that you are a knowledgable guy,
Try me with computers . . .

but this goes against RF theory, how can you back this up? When I say big
aeial I mean one with more gain.
Yes, but the difference in gain between, say a ten element aerial and the
biggest high gain aerial on the market is only about 7dB. That amounts to a
three way split. The installation of a big high gain aerial, with all that
implies in terms of appearance, windage, and fixings, is definitely not the
way to acquire an extra 7dB for distribution! If you want to do such a barmy
thing you'd be better with three 10-elements on the roof!


But anyway, let's consider your proposition.
0dBmV from the aerial
-2dBmV in the loft
-26dBmV after the 24dB splitter loss
-30dBmV after the downlead loss (that's optimistic unless the flats are
only about a yard wide)
-32dBmV after the outlet and flylead loss.


True I did conviently forget some of the losses, especially the coax
losses. I'd revise my figure to 70-80dbuV required at the aerial.
Ah. Well, if you can obtain 20dBmV of DTT signal from the aerial I'd be with
you all the way. You'd need to be very close to the tx though! Remember that
the analogue channels would normally be at 40dBmV for this DTT level. I've
seen such signal levels. Four miles from Crystal Palace with clear
line-of-site. 250m from the Crosspool tx on top of a tall building, so
almost level with the tx aerials. But such signal levels are only available
at such locations, very close to high or medium powered transmitters. As
such they are abnormal.


I'm not sure what figures you're working in but -32dBm will easily drive
loads of TVs. A DTV reciever needs about 28dBuV (-80dBm ish) of mux to
get a good picture, more for a stable picture/weather etc (as long as any
adjancent analogue is proportional)
Of course, as every schoolboy knows, the picture is always good on digital
until it isn't. I agree, 'more for a stable picture/weather'. Actually, much
more. The agreed figures have recently been discussed on this newsgroup, and
amount to a safe minimum of around -20dBmV. But for any respectable system
you shouldn't provide less than -10dBmV at the outlet. Think about local
interference from the TV set itself, etc.


It ain't gonna work is it?

Why not? It does, I have designed several setups for test in labs and
factories for companies I have worked for.
When I was ten I designed a machine for squirting water at the neighbour's
baby. Fortunately the mere design completion was not enough to ensure
effective operation of the equipment.

Your systems, I'm sorry to tell you, are a total botch if they provide only
barely adequate levels. You can walk away from a system where every outlet
is giving good reception, but if there's no allowance built in the job is a
botch.

All passive distrbution its
all about the level you start with.
Yes . . . and the losses on the system.


I of course realise it won't work if there isn't enough signal but many of
these places are near transmitters.
To be honest this job isn't just about simple arithmetic. You should never
ever install a system that provides barely adequate levels. In the real
world component values vary, cable losses increase with time, deaf receivers
are common, and ****ty 31p flyleads are sold for £4.50.

Bill

Digital TV for Residential Care Homes
 

On Fri, 25 Jul 2008 01:37:19 +0100, "Bill Wright"
wrote:


"Tony" wrote in message ...
Bill Wright wrote:
Putting up a big aerial has an almost negligible effect on how many times
you can split the signal.

Bill I know who you are,
Hell! And you know where I am!

and that you are a knowledgable guy,
Try me with computers . . .

but this goes against RF theory, how can you back this up? When I say big
aeial I mean one with more gain.
Yes, but the difference in gain between, say a ten element aerial and the
biggest high gain aerial on the market is only about 7dB. That amounts to a
three way split. The installation of a big high gain aerial, with all that
implies in terms of appearance, windage, and fixings, is definitely not the
way to acquire an extra 7dB for distribution! If you want to do such a barmy
thing you'd be better with three 10-elements on the roof!


But anyway, let's consider your proposition.
0dBmV from the aerial
-2dBmV in the loft
-26dBmV after the 24dB splitter loss
-30dBmV after the downlead loss (that's optimistic unless the flats are
only about a yard wide)
-32dBmV after the outlet and flylead loss.


True I did conviently forget some of the losses, especially the coax
losses. I'd revise my figure to 70-80dbuV required at the aerial.
Ah. Well, if you can obtain 20dBmV of DTT signal from the aerial I'd be with
you all the way. You'd need to be very close to the tx though! Remember that
the analogue channels would normally be at 40dBmV for this DTT level. I've
seen such signal levels. Four miles from Crystal Palace with clear
line-of-site. 250m from the Crosspool tx on top of a tall building, so
almost level with the tx aerials. But such signal levels are only available
at such locations, very close to high or medium powered transmitters. As
such they are abnormal.


I'm not sure what figures you're working in but -32dBm will easily drive
loads of TVs. A DTV reciever needs about 28dBuV (-80dBm ish) of mux to
get a good picture, more for a stable picture/weather etc (as long as any
adjancent analogue is proportional)
Of course, as every schoolboy knows, the picture is always good on digital
until it isn't. I agree, 'more for a stable picture/weather'. Actually, much
more. The agreed figures have recently been discussed on this newsgroup, and
amount to a safe minimum of around -20dBmV. But for any respectable system
you shouldn't provide less than -10dBmV at the outlet. Think about local
interference from the TV set itself, etc.


It ain't gonna work is it?

Why not? It does, I have designed several setups for test in labs and
factories for companies I have worked for.
When I was ten I designed a machine for squirting water at the neighbour's
baby. Fortunately the mere design completion was not enough to ensure
effective operation of the equipment.

Your systems, I'm sorry to tell you, are a total botch if they provide only
barely adequate levels. You can walk away from a system where every outlet
is giving good reception, but if there's no allowance built in the job is a
botch.

All passive distrbution its
all about the level you start with.
Yes . . . and the losses on the system.


I of course realise it won't work if there isn't enough signal but many of
these places are near transmitters.
To be honest this job isn't just about simple arithmetic. You should never
ever install a system that provides barely adequate levels. In the real
world component values vary, cable losses increase with time, deaf receivers
are common, and ****ty 31p flyleads are sold for £4.50.

Bill


I did a test with cheap flyleads using my meter, and was surprised at
the difference compared to a short run of CT100. Most flyleads (0.5m)
had up to 2dBuV loss compared to the same length CT100 which, with
DTT, can be the difference between getting a signal and not.

Marky P.

Digital TV for Residential Care Homes
 

In article ,
Marky P wrote:

I did a test with cheap flyleads using my meter, and was surprised at
the difference compared to a short run of CT100. Most flyleads (0.5m)
had up to 2dBuV loss compared to the same length CT100 which, with
DTT, can be the difference between getting a signal and not.

the 'best' one I measured was giving a loss of only a few dBs on ch 39, but
20dB at ch 66!

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

Digital TV for Residential Care Homes
 

charles wrote:
In article ,
Marky P wrote:

I did a test with cheap flyleads using my meter, and was surprised at
the difference compared to a short run of CT100. Most flyleads (0.5m)
had up to 2dBuV loss compared to the same length CT100 which, with
DTT, can be the difference between getting a signal and not.

the 'best' one I measured was giving a loss of only a few dBs on ch 39, but
20dB at ch 66!


Most accessory fly leads are not shielded at the plug-cable joint, this
results in the large losses. Sheilded plug leads cost typically 30%
more in volume.

--
Tony

Digital TV for Residential Care Homes
 

Bill Wright wrote:
"Tony" wrote in message ...
Bill Wright wrote:
Putting up a big aerial has an almost negligible effect on how many times
you can split the signal.
Bill I know who you are,
Hell! And you know where I am!

and that you are a knowledgable guy,
Try me with computers . . .

but this goes against RF theory, how can you back this up? When I say big
aeial I mean one with more gain.
Yes, but the difference in gain between, say a ten element aerial and the
biggest high gain aerial on the market is only about 7dB. That amounts to a
three way split. The installation of a big high gain aerial, with all that
implies in terms of appearance, windage, and fixings, is definitely not the
way to acquire an extra 7dB for distribution! If you want to do such a barmy
thing you'd be better with three 10-elements on the roof!


Fair enough, to be honest aerials are not my expertise, I am mostly
working with generators/modulators. Maybe my lastest home installation
is just better quality/newer than the one done by Ondigital on my older
house.

I have 2 known locations in the same area, 1 is a 10 element higher up
the hill with no or little obstructions, and is quite marginal in bad
weather and the other is a 43 element behind these trees. The 43
element gets a signal in that is alot more that the difference in aerial
gain. There could be other factors like wet connections/better coax. I
shall be checking it the near future.

Ah. Well, if you can obtain 20dBmV of DTT signal from the aerial I'd be with
you all the way. You'd need to be very close to the tx though!

I'm not familiar with these units and cannot find a converter, they
don't seem to be dBm(W) or dBuV.



Your systems, I'm sorry to tell you, are a total botch if they provide only
barely adequate levels. You can walk away from a system where every outlet
is giving good reception, but if there's no allowance built in the job is a
botch.


I agree a system with barely adequate level would not be robust, indeed
we could not afford the line to be stopped because of a slightly damaged
bit of coax or bad weather.

All passive distrbution its
all about the level you start with.
Yes . . . and the losses on the system.

I of course realise it won't work if there isn't enough signal but many of
these places are near transmitters.
To be honest this job isn't just about simple arithmetic. You should never
ever install a system that provides barely adequate levels. In the real
world component values vary, cable losses increase with time, deaf receivers
are common, and ****ty 31p flyleads are sold for £4.50.


I don't think we dissagree on that, I just thought Aerial gain was the
way to eliminate amplifiers, and still think that it can. But where it
would work is another issue, I don't have the practical experience for
that. I just had the feeling that it is too easily excluded in favour
of expensive amplified system. Heavy duty coax is also another way to
boost levels, often ignored. And the performance of a 20dB distribution
amp is often over estimated, so maybe 7dB of aerial gain is enough.

I have to say, though, that your estimates of required margins are
probably alot more than mine, that is probably representative of our
difference worlds, but that is another debate. While my 80dBuV might be
enough to supply 64 TVs it might not provide enough practical margin to
account for aging/deterioration, but then in my world consumers don't
really care about life time (well not enough to pay extra for it).

--
Tony