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TV Freeview picture breaking up, New 4G transmitter and Aeroplanes



 
 
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  #1  
Old September 24th 15, 05:32 PM posted to uk.tech.digital-tv,uk.d-i-y
john west
external usenet poster
 
Posts: 5
Default TV Freeview picture breaking up, New 4G transmitter and Aeroplanes

Suddenly in the last month or so our Freeview television picture is
suddenly breaking up.

We got a visit from the 'at800' Engineer who fitted a filter in-line
before our television aerial amplifier. Apparently we have a new phone
4G transmitter installed quite near.

The engineer said his readings were within accepted limits.

We are about 15 miles north east of Heathrow Airport and get a lot of
planes, they are sufficiently high so that we cannot read the markings
on the planes. We are about thirteen miles north west of the crystal
palace transmitter.

Now every time a plane goes over the picture and sound break up and
that's very often.

Everything worked fine before until about a month or so ago, and we have
carefully checked all connections and leads and have bought a new Aerial.

Any suggestions please.
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  #2  
Old September 24th 15, 06:10 PM posted to uk.tech.digital-tv,uk.d-i-y
Java Jive[_2_]
external usenet poster
 
Posts: 1,774
Default TV Freeview picture breaking up, New 4G transmitter and Aeroplanes

Congratulations, it seems you have invented radar ... Pity you're not
the first !-)

On Thu, 24 Sep 2015 18:32:59 +0100, john west
wrote:

Suddenly in the last month or so our Freeview television picture is
suddenly breaking up.

We got a visit from the 'at800' Engineer who fitted a filter in-line
before our television aerial amplifier. Apparently we have a new phone
4G transmitter installed quite near.

The engineer said his readings were within accepted limits.

We are about 15 miles north east of Heathrow Airport and get a lot of
planes, they are sufficiently high so that we cannot read the markings
on the planes. We are about thirteen miles north west of the crystal
palace transmitter.

Now every time a plane goes over the picture and sound break up and
that's very often.

Everything worked fine before until about a month or so ago, and we have
carefully checked all connections and leads and have bought a new Aerial.

Any suggestions please.

--
================================================== ======
Please always reply to ng as the email in this post's
header does not exist. Or use a contact address at:
http://www.macfh.co.uk/JavaJive/JavaJive.html
http://www.macfh.co.uk/Macfarlane/Macfarlane.html
  #3  
Old September 24th 15, 07:06 PM posted to uk.tech.digital-tv,uk.d-i-y
Mark Carver
external usenet poster
 
Posts: 7,633
Default TV Freeview picture breaking up, New 4G transmitter andAeroplanes

On 24/09/2015 19:10, Java Jive wrote:
Congratulations, it seems you have invented radar ... Pity you're not
the first !-)


I can't believe reflections from aircraft (as high as that) could punch
out enough of the 8 MHz worth of COFDM 'lump' to cause such a severe and
noticeable effect ?

--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #4  
Old September 24th 15, 07:18 PM posted to uk.d-i-y,uk.tech.digital-tv
Dave Liquorice[_2_]
external usenet poster
 
Posts: 239
Default TV Freeview picture breaking up, New 4G transmitter and Aeroplanes

On Thu, 24 Sep 2015 18:32:59 +0100, john west wrote:

Now every time a plane goes over the picture and sound break up and
that's very often.

Everything worked fine before until about a month or so ago, and we have
carefully checked all connections and leads and have bought a new
Aerial.

Any suggestions please.


Has the set "helpfully" retuned itself to a different transmitter.
You'll need to find the channel numbers each MUX is transmitted on
from near by transmitters and dig through the sets menus to find out
what it is using.

--
Cheers
Dave.



  #5  
Old September 24th 15, 07:19 PM posted to uk.tech.digital-tv,uk.d-i-y
Java Jive[_2_]
external usenet poster
 
Posts: 1,774
Default TV Freeview picture breaking up, New 4G transmitter and Aeroplanes

On Thu, 24 Sep 2015 20:06:49 +0100, Mark Carver
wrote:

On 24/09/2015 19:10, Java Jive wrote:
Congratulations, it seems you have invented radar ... Pity you're not
the first !-)


I can't believe reflections from aircraft (as high as that) could punch
out enough of the 8 MHz worth of COFDM 'lump' to cause such a severe and
noticeable effect ?


'Twas tongue in cheek, didn't you spot the smiley? I don't know
enough to make a serious comment, but I'm sure someone'll be along
shortly ...
--
================================================== ======
Please always reply to ng as the email in this post's
header does not exist. Or use a contact address at:
http://www.macfh.co.uk/JavaJive/JavaJive.html
http://www.macfh.co.uk/Macfarlane/Macfarlane.html
  #6  
Old September 24th 15, 07:22 PM posted to uk.tech.digital-tv,uk.d-i-y
Mark Carver
external usenet poster
 
Posts: 7,633
Default TV Freeview picture breaking up, New 4G transmitter andAeroplanes

On 24/09/2015 20:19, Java Jive wrote:
On Thu, 24 Sep 2015 20:06:49 +0100, Mark Carver
wrote:

On 24/09/2015 19:10, Java Jive wrote:
Congratulations, it seems you have invented radar ... Pity you're not
the first !-)


I can't believe reflections from aircraft (as high as that) could punch
out enough of the 8 MHz worth of COFDM 'lump' to cause such a severe and
noticeable effect ?


'Twas tongue in cheek, didn't you spot the smiley? I don't know
enough to make a serious comment, but I'm sure someone'll be along
shortly ...


Oh I know that, I was really doubting the OP's belief that reflections
from aircraft are a likely culprit (in his case).



--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #7  
Old September 24th 15, 07:50 PM posted to uk.d-i-y,uk.tech.digital-tv
charles[_2_]
external usenet poster
 
Posts: 699
Default TV Freeview picture breaking up, New 4G transmitter and Aeroplanes

In article o.uk, Dave
Liquorice wrote:
On Thu, 24 Sep 2015 18:32:59 +0100, john west wrote:


Now every time a plane goes over the picture and sound break up and
that's very often.

Everything worked fine before until about a month or so ago, and we
have carefully checked all connections and leads and have bought a new
Aerial.

Any suggestions please.


Has the set "helpfully" retuned itself to a different transmitter. You'll
need to find the channel numbers each MUX is transmitted on from near by
transmitters and dig through the sets menus to find out what it is using.


15 miles NE of Heathrow could be in the Alexandra Palace area, if it isn't
Crystal Palace itself.

How many programmes can you get? This will determine whether you are
getting a main station or a relay

--
Please note new email address:

  #8  
Old September 24th 15, 08:52 PM posted to uk.tech.digital-tv,uk.d-i-y
Bill Wright[_2_]
external usenet poster
 
Posts: 9,381
Default TV Freeview picture breaking up, New 4G transmitter and Aeroplanes

john west wrote:
Suddenly in the last month or so our Freeview television picture is
suddenly breaking up.

We got a visit from the 'at800' Engineer who fitted a filter in-line
before our television aerial amplifier. Apparently we have a new phone
4G transmitter installed quite near.

The engineer said his readings were within accepted limits.

We are about 15 miles north east of Heathrow Airport and get a lot of
planes, they are sufficiently high so that we cannot read the markings
on the planes. We are about thirteen miles north west of the crystal
palace transmitter.

Now every time a plane goes over the picture and sound break up and
that's very often.

Everything worked fine before until about a month or so ago, and we have
carefully checked all connections and leads and have bought a new Aerial.

Any suggestions please.


This sounds like a classic case of 'misleading fault reporting', to be
honest. I think you'll find that there's no connection between the
planes and the fault. Please don't be offended, but customers often
assign irrelevant 'causes' to their reception faults. It can be anything
from the weather, 'the number of aerials sucking on it', the radio ham
across the road coming home from work, next door's dog barking and the
noise affecting the waves, pretty well owt really.

Planes take a while to pass over when they're high up. How does that fit
in with the picture break up? What about the planes you don't see? Any
break up when you can't see any planes?

But assuming you aren't simply having a laugh it might be interesting to
discuss the scenario you describe.

Planes so high up will probably be in an area of relatively low field
strength, so any reflections (which might have a rapid additive and
subtractive effect on the signal output of your aerial) will be
similarly reduced in strength. Beam tilt at the tx is the reason for
this. Apart from the obvious reasons for beam tilt there's the fact that
such high powered tx's aren't allowed to radiate much above the horizon
because of the possibility of EMI in aeroplanes.

Yes, 'aeroplane flutter' was an issue in the analogue days, very rare
under circumstances such as yours for UHF but quite common for VHF. The
main reason for this is that UHF aerials are far more directional than
VHF ones. Indeed some types of VHF aerial had no discrimination
whatsoever against signals from above (anyone like to name two examples,
one of each polarisation?)

Any reflection from a high plane would arrive sufficiently delayed for
the modulation system in use by digital TV to ignore it (it's expressly
designed to do just that), unless it was so strong that it confused the
receiver's AGC. And that's impossible, really, because your aerial will
be discriminating against the reflection by 10 or 20dB (which is a lot.)

It isn't possible that any interference actually generated by the plane
will affect your reception. Think what a fuss there's be near airports
if that was the case!

When you say you've bought a new aerial, well, buying the thing is only
a small part of the process! Is it the right type, pointing the right
way? Any obstructions? And there are other things. Just because you've
had good reception until now doesn't mean thing really. I'm guessing
that the signal from your aerial is marginal, and something is causing
occasional break up.

I must apologise for the length of this reply but it's either skulk in
here or talk to a damnfool friend of my wife who's called round
seemingly to get us to join the Green Party. I just don't want to cause
an upset. . .

Bill
  #9  
Old September 24th 15, 09:17 PM posted to uk.tech.digital-tv,uk.d-i-y
charles[_2_]
external usenet poster
 
Posts: 699
Default TV Freeview picture breaking up, New 4G transmitter and Aeroplanes

In article ,
Bill Wright wrote:
john west wrote:
Suddenly in the last month or so our Freeview television picture is
suddenly breaking up.

We got a visit from the 'at800' Engineer who fitted a filter in-line
before our television aerial amplifier. Apparently we have a new phone
4G transmitter installed quite near.

The engineer said his readings were within accepted limits.

We are about 15 miles north east of Heathrow Airport and get a lot of
planes, they are sufficiently high so that we cannot read the markings
on the planes. We are about thirteen miles north west of the crystal
palace transmitter.

Now every time a plane goes over the picture and sound break up and
that's very often.

Everything worked fine before until about a month or so ago, and we have
carefully checked all connections and leads and have bought a new Aerial.

Any suggestions please.


This sounds like a classic case of 'misleading fault reporting', to be
honest. I think you'll find that there's no connection between the
planes and the fault. Please don't be offended, but customers often
assign irrelevant 'causes' to their reception faults. It can be anything
from the weather, 'the number of aerials sucking on it', the radio ham
across the road coming home from work, next door's dog barking and the
noise affecting the waves, pretty well owt really.


Planes take a while to pass over when they're high up. How does that fit
in with the picture break up? What about the planes you don't see? Any
break up when you can't see any planes?


But assuming you aren't simply having a laugh it might be interesting to
discuss the scenario you describe.


Planes so high up will probably be in an area of relatively low field
strength, so any reflections (which might have a rapid additive and
subtractive effect on the signal output of your aerial) will be
similarly reduced in strength. Beam tilt at the tx is the reason for
this. Apart from the obvious reasons for beam tilt there's the fact that
such high powered tx's aren't allowed to radiate much above the horizon
because of the possibility of EMI in aeroplanes.


Yes, 'aeroplane flutter' was an issue in the analogue days, very rare
under circumstances such as yours for UHF but quite common for VHF. The
main reason for this is that UHF aerials are far more directional than
VHF ones. Indeed some types of VHF aerial had no discrimination
whatsoever against signals from above (anyone like to name two examples,
one of each polarisation?)


Any reflection from a high plane would arrive sufficiently delayed for
the modulation system in use by digital TV to ignore it (it's expressly
designed to do just that), unless it was so strong that it confused the
receiver's AGC. And that's impossible, really, because your aerial will
be discriminating against the reflection by 10 or 20dB (which is a lot.)


It isn't possible that any interference actually generated by the plane
will affect your reception. Think what a fuss there's be near airports
if that was the case!


When you say you've bought a new aerial, well, buying the thing is only
a small part of the process! Is it the right type, pointing the right
way? Any obstructions? And there are other things.


yes, are you using the old downlead? It might have got damaged.
interesting I responded to a cry of "picture break up" from some neighbours
and found the fault was due to badly fitted plugs on the aerial downlead
behind the set. A drop of solder cure that! Give all the lead behind the
set a good shake. That might show up something.


Just because you've
had good reception until now doesn't mean thing really. I'm guessing
that the signal from your aerial is marginal, and something is causing
occasional break up.


I must apologise for the length of this reply but it's either skulk in
here or talk to a damnfool friend of my wife who's called round
seemingly to get us to join the Green Party. I just don't want to cause
an upset. . .


Bill


--
Please note new email address:

  #10  
Old September 24th 15, 09:57 PM posted to uk.tech.digital-tv,uk.d-i-y
Michael Chare[_5_]
external usenet poster
 
Posts: 64
Default TV Freeview picture breaking up, New 4G transmitter andAeroplanes

On 24/09/2015 18:32, john west wrote:

Everything worked fine before until about a month or so ago, and we have
carefully checked all connections and leads and have bought a new Aerial.

Any suggestions please.


Wait for the wind to change, the planes will then take a different path.


--
Michael Chare
 




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