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COM7&8 on Crystal Palace



 
 
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  #11  
Old April 17th 19, 07:40 PM posted to uk.tech.digital-tv
Mark Carver
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Default COM7&8 on Crystal Palace

On 17/04/2019 18:30, tim... wrote:

Umm, just for comparison what do you get on Ch 30 (the main T2-HD mux) ?


quality 100%
strength 92%


I think that clinches it ! You need a wideband.


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  #12  
Old April 17th 19, 08:07 PM posted to uk.tech.digital-tv
Mark Carver
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Default COM7&8 on Crystal Palace

On 17/04/2019 19:40, NY wrote:

Of course, the quality and strength values are probably very non-linear:
a strength of 92% may not be anything like twice the power/voltage of a
strength of 45%. You can *perhaps* infer that a larger % figure is
better, but maybe even that is an assumption too far :-)


Which is why signal and power ratios are expressed logarithmically (in
the form of Decibels) and not linearly.

All that said, and drawing on empirical experience with bargarph style
signal meters, it's pretty evident COM 7/8 are way down in level
compared to the others.

From CP they are only actually 8dB or so lower in power. All else being
equal I'd expect them to be easily receivable with a wideband aerial
(assuming quality co-ax etc too)
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Mark
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  #13  
Old April 17th 19, 08:15 PM posted to uk.tech.digital-tv
Robin[_10_]
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Default COM7&8 on Crystal Palace

On 17/04/2019 12:53, tim... wrote:
Hi,

I just moved into my new house and (as I have been relying on Freesat at
the previous one) had to by a new HD receiver for my "HR Ready" TV.

When I tuned it in, it found all of the channels on COM7&8 but when I
select them they are dark.

I am 3-4 miles away from the transmitter, so presumably we still have a
narrowband aerial.

But if it can't see them to show them now, how did it find them when I
tuned in?* Might they come and go at different times of the day
depending upon the weather?


IMVVLE TVs will tune on a very weak signal (cf. "there's something
written on this") but then decline to give you any sound or picture (cf.
"but I'm buggered if I can make out what it says").


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  #14  
Old April 17th 19, 08:40 PM posted to uk.tech.digital-tv
NY
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Posts: 1,669
Default COM7&8 on Crystal Palace

"Robin" wrote in message
...
IMVVLE TVs will tune on a very weak signal (cf. "there's something written
on this") but then decline to give you any sound or picture (cf. "but I'm
buggered if I can make out what it says").


The first step is to scan the UHF spectrum for a COFDM signals for a
multiplex.

Then I can imagine that if the TV can decode the header data tables, maybe
looking at several copies of the packets that contain the list of channel
names, the LCNs, the stream IDs etc, to "fill in the missing bits", it will
add the channels to the TV's list that it stores for later use. But when it
tries to decode the video and audio streams, the bit error rate is too high
to produce anything usable because of the poor SNR.

  #15  
Old April 18th 19, 09:07 AM posted to uk.tech.digital-tv
Brian Gaff
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Default COM7&8 on Crystal Palace

Here just across the valley from the crystal Palace mast, if I go upstairs
with a tv, I can get all stations on a bit of wire about 8 inches long.
Sounds a bit odd if an aerial cannot resolve them. I think there is more
going on than meets the eye.
Brian

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"Scott" wrote in message
...
On Wed, 17 Apr 2019 12:53:27 +0100, "tim..."
wrote:

Hi,

I just moved into my new house and (as I have been relying on Freesat at
the
previous one) had to by a new HD receiver for my "HR Ready" TV.

When I tuned it in, it found all of the channels on COM7&8 but when I
select
them they are dark.

I am 3-4 miles away from the transmitter, so presumably we still have a
narrowband aerial.

But if it can't see them to show them now, how did it find them when I
tuned
in? Might they come and go at different times of the day depending upon
the
weather?

And as there's only PSB that I'm likely to have any interest in watching,
is
it worth getting the aerial replaced given that PSB7&8 will be turned off
at
some point in the future - does anyone know what date that will be?

Maybe a bit different for me but I have Group B for a transmitter
probably 25 miles away and I get the BBC Four etc fine on HD.

You are more 'out of band' but your signal strength must be vastly
more powerful than mine given you are only about a quarter of the
distance. When I live in Clapham (pre-digital) the signal strength
was so high I needed an attenuator.



  #16  
Old April 18th 19, 09:11 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 7,673
Default COM7&8 on Crystal Palace

Also it will be then that my old Goodmans box finally becomes a door stop
I'd imagine as it cannot do hd encoded multiplexes at all.

I fully understand that its stupid having duplicated channels though, and so
progress marches on but I bet there will be quite a few viewers suddenly
dismayed at the loss of some channels on the day.
Brian

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"NY" wrote in message
o.uk...
"Mark Carver" wrote in message
...
The muxes are due to close no later than June 30th 2022.


Are there any plans published yet as to what will happen to the channels
that are currently carried by COM7 and COM8? Will homes be found for them
in other multiplexes (if they are converted from DVB-T to DVB-T2) or will
they be dropped from Freeview altogether. I'd miss BBC Four HD. Shame that
wasn't given a home in PSB3 right from the start.



  #17  
Old April 18th 19, 09:13 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 7,673
Default COM7&8 on Crystal Palace

Oh dear, oh dear, one also wonders why they made it in the first place. A
good bandwidth allocation for sd would I am told do just as well. Of course
nowadays since losing my sight, I find the screen an expensive extra...:-)
Brian

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"tim..." wrote in message
...


"NY" wrote in message
o.uk...
"Mark Carver" wrote in message
...
The muxes are due to close no later than June 30th 2022.


Are there any plans published yet as to what will happen to the channels
that are currently carried by COM7 and COM8? Will homes be found for them
in other multiplexes (if they are converted from DVB-T to DVB-T2) or will
they be dropped from Freeview altogether. I'd miss BBC Four HD. Shame
that wasn't given a home in PSB3 right from the start.


but who is it who wants QVC HD?

tim





 




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