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Crystal Palace Issues



 
 
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  #51  
Old April 3rd 18, 03:45 PM posted to uk.tech.digital-tv
John[_21_]
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Default Crystal Palace Issues

On Saturday, 31 March 2018 10:20:09 UTC+1, Brian Gaff wrote:
I'd not bank on it, but yes, you are correct. Its only a temp move while
other transmitters are also moved that would otherwise interfere.
I simply cannot understand why this issue was not expected?
Brian


It has come as something of a surprise, even to the local authority landlord. The communal system is Group A, and you would have thought that this would have been upgraded PRIOR to the reallocation!

As it is, for the communal system, we have to wait until somebody wins the contract to change all of the communal systems on all of the Council's buildings, of which there are many.

John
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  #52  
Old April 3rd 18, 03:48 PM posted to uk.tech.digital-tv
John[_21_]
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Default Crystal Palace Issues

On Saturday, 31 March 2018 10:12:51 UTC+1, Brian Gaff wrote:
I believe also that when other channels move they will probably have to move
the channels down again.
I just wonder who signs off on this rubbish. However I'm surprised at that
height that you get no signal at all. I'd wonder if perhaps there is a low
pass filter in use causing this on your feed?
Brian

--


The cable run is about 70m and is not amplified. There should not be any filters attached to my private aerial, though there must almost certainly be on the communal system.

But surely a Group A aerial is built to resist receiving UHF 55/56 anyway?

John
  #53  
Old April 3rd 18, 03:51 PM posted to uk.tech.digital-tv
Scott[_2_]
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Default Crystal Palace Issues

On Tue, 3 Apr 2018 08:48:43 -0700 (PDT), John
wrote:

On Saturday, 31 March 2018 10:12:51 UTC+1, Brian Gaff wrote:
I believe also that when other channels move they will probably have to move
the channels down again.
I just wonder who signs off on this rubbish. However I'm surprised at that
height that you get no signal at all. I'd wonder if perhaps there is a low
pass filter in use causing this on your feed?
Brian

--


The cable run is about 70m and is not amplified. There should not be any filters attached to my private aerial, though there must almost certainly be on the communal system.

But surely a Group A aerial is built to resist receiving UHF 55/56 anyway?

I am still hoping that my Group B aerial will work (not from CP
obviously) but will need to wait and see.
  #54  
Old April 3rd 18, 05:57 PM posted to uk.tech.digital-tv
Terry Casey[_2_]
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Posts: 768
Default Crystal Palace Issues

In article 20d04a6d-2f35-42ab-92a4-ac6ab5628909
@googlegroups.com, says...


But surely a Group A aerial is built to resist receiving UHF 55/56 anyway?


It sure is!

Look at the red line in this graph for the response of a
Group A aerial:

http://aerialsandtv.com/_wp_generate...e4f6_01_1a.jpg

--

Terry

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  #56  
Old April 3rd 18, 07:13 PM posted to uk.tech.digital-tv
Mark Carver
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Default Crystal Palace Issues

On 03/04/2018 16:37, John wrote:

No they don't use the same channels except for the new 55/56 allocation,
and you can't do anything about that.


If the new aerial, when eventually fitted, is able to get 55/56 from more than one source, will this cause issues?


Unlikely, even if the distant transmission is in the same direction, the
signal from Crystal P will be tens of dB higher.

I've worked out (I think) the maximum path difference for the COM 7 and
8 SFNs (assuming all transmitters won't have additional timing offsets)
is 66.9km. (DAB radio is about 75km). If the path difference exceeds
that, AND the additional transmission(s) will be of a level that
violates the C/N ratio, then there will be problems (probably !)


--
Mark
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  #57  
Old April 3rd 18, 07:57 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,448
Default Crystal Palace Issues

On 03/04/2018 16:37, John wrote:

Just a moment ago, the aerial chappie sent by Digital TV did some readings in my living room with his bright yellow meter reader. No issues with the Group A end, and zero reading at 55 and 56.


But what was the loss on the cable on the Gp A channels? That would
indicate whether cable had moisture damage. He really needed to measure
the signal as it entered and left the cable.

If the new aerial, when eventually fitted, is able to get 55/56 from more than one source, will this cause issues?


That all depends...

Your 70m cable will lose more on the higher channels, especially if it
has rubbed anywhere and got a bit of damp in it. That could easily
explain the problem.


When they come to swap the aerials, I shall ask them to have a look for water ingress. This was a problem with my previous Group A aerial The top part of the cable had to be chopped off and replaced. As a result, they put far more tape on the replacement to, hopefully, keep the water out.


If the top part of the cable once had water in it the whole length of
the cable will not be performing properly, even if it's been dried out.
The response will be almost normal on some frequencies and poor on
others, in a random way but generally worse on the higher channels.


The CP signal will be so strong that the aerial could well be faulty and
still provide enough signal to seem OK. But that would show up on 55/56.


I think it's likely that the wideband aerial will result in weak but
probably just about adequate signal at the bottom end of the cable. Or
they might be just a bit too weak to be reliable.

One thing is for sure. You need a new downlead. It needs to be really
good quality cable for a run of that length. It just isn't good practice
to try to get away with old damp cable.

Bill
  #58  
Old April 3rd 18, 07:59 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,448
Default Crystal Palace Issues

On 03/04/2018 16:45, John wrote:
On Saturday, 31 March 2018 10:20:09 UTC+1, Brian Gaff wrote:
I'd not bank on it, but yes, you are correct. Its only a temp move while
other transmitters are also moved that would otherwise interfere.
I simply cannot understand why this issue was not expected?
Brian


It has come as something of a surprise, even to the local authority landlord. The communal system is Group A, and you would have thought that this would have been upgraded PRIOR to the reallocation!

As it is, for the communal system, we have to wait until somebody wins the contract to change all of the communal systems on all of the Council's buildings, of which there are many.

John

Quite often councils refuse to pay for this sort of work. They weigh the
provision of a few TV channels against other priorities.

Bill
  #59  
Old April 3rd 18, 08:01 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,448
Default Crystal Palace Issues

On 03/04/2018 16:51, Scott wrote:

But surely a Group A aerial is built to resist receiving UHF 55/56 anyway?


They don't exactly 'resist' it. They are sort of ambivalent I'd say, in
an unpredictable way. You, know, like when you chat up a bonny lass.

Bill
  #60  
Old April 5th 18, 11:30 AM posted to uk.tech.digital-tv
tony sayer
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Posts: 5,001
Default Crystal Palace Issues

In article ,
Terry Casey scribeth thus
In article 20d04a6d-2f35-42ab-92a4-ac6ab5628909
, says...


But surely a Group A aerial is built to resist receiving UHF 55/56 anyway?


It sure is!

Look at the red line in this graph for the response of a
Group A aerial:

http://aerialsandtv.com/_wp_generate...e4f6_01_1a.jpg


Yess - since when has the Yagi array been known for being a wideband
unit?..
--
Tony Sayer




 




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