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uk.tech.digital-tv (Digital TV - General) (uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

Paranoia or real effect?



 
 
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  #1  
Old March 11th 18, 10:07 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 7,250
Default Paranoia or real effect?

I was talking to somebody a week or so back who swears their freeview goes
blacky and stutters whenever a plane from Heathrow goes over.
Now in the good old analogue days you could detect aircraft flutter quite
easily, how would you go about it on a digital system. I did not rise to the
bait of suggesting I go around as to be honest there would be little I could
do.

We are after all in a very strong signal area here, and I'd have thought it
most unlikely that a properly installed aerial would have this problem,
which leaves either paranoia or a faulty installation.

Brian

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  #2  
Old March 11th 18, 10:11 AM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Posts: 649
Default Paranoia or real effect?

On Sunday, 11 March 2018 11:07:04 UTC, Brian Gaff wrote:
I was talking to somebody a week or so back who swears their freeview goes
blacky and stutters whenever a plane from Heathrow goes over.


In Yorkshire.

Now in the good old analogue days you could detect aircraft flutter quite
easily, how would you go about it on a digital system. I did not rise to the
bait of suggesting I go around as to be honest there would be little I could
do.

We are after all in a very strong signal area here, and I'd have thought it
most unlikely that a properly installed aerial would have this problem,
which leaves either paranoia or a faulty installation.

Brian


Perhaps s/he has Freesat and is very close to the airport. Can't see a mechanism otherwise.


  #3  
Old March 11th 18, 11:30 AM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,326
Default Paranoia or real effect?

In article , R.
Mark Clayton wrote:
We are after all in a very strong signal area here, and I'd have
thought it most unlikely that a properly installed aerial would have
this problem, which leaves either paranoia or a faulty installation.

Brian


Perhaps s/he has Freesat and is very close to the airport. Can't see a
mechanism otherwise.


RX being overloaded by some signals from the plane adding to the "strong"
ones from Freeview? i.e. matter of an RX that accepts and is overloaded by
out of band input at a high power level?

--
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Electronics https://www.st-andrews.ac.uk/~www_pa...o/electron.htm
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Audio Misc http://www.audiomisc.co.uk/index.html

  #4  
Old March 11th 18, 12:22 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Posts: 649
Default Paranoia or real effect?

On Sunday, 11 March 2018 13:11:25 UTC, Jim Lesurf wrote:
In article , R.
Mark Clayton wrote:
We are after all in a very strong signal area here, and I'd have
thought it most unlikely that a properly installed aerial would have
this problem, which leaves either paranoia or a faulty installation.

Brian


Perhaps s/he has Freesat and is very close to the airport. Can't see a
mechanism otherwise.


RX being overloaded by some signals from the plane adding to the "strong"
ones from Freeview? i.e. matter of an RX that accepts and is overloaded by
out of band input at a high power level?


Faintly possible, but AFAIK the only big output from a plane is ATC in AM VHF [for now].
  #5  
Old March 11th 18, 01:14 PM posted to uk.tech.digital-tv
Chris Green
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Posts: 178
Default Paranoia or real effect?

Brian Gaff wrote:
I was talking to somebody a week or so back who swears their freeview goes
blacky and stutters whenever a plane from Heathrow goes over.
Now in the good old analogue days you could detect aircraft flutter quite
easily, how would you go about it on a digital system. I did not rise to the
bait of suggesting I go around as to be honest there would be little I could
do.

We certainly got that effect when watching FreeView on our boat moored
very close to London City Airport. When I say close I mean *close*,
the runway lights continued through the marina.

I guess we probably didn't have a particularly strong signal but we
did have a directional aerial outside pointing in the right direction
(except when the wind blew it wonky).

The effect was usually breaking up and then loss of picture (and
sound) for a few seconds when planes went over.


We are after all in a very strong signal area here, and I'd have thought it
most unlikely that a properly installed aerial would have this problem,
which leaves either paranoia or a faulty installation.

Brian


--
Chris Green
·
  #6  
Old March 11th 18, 01:37 PM posted to uk.tech.digital-tv
Peter Duncanson
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Posts: 4,272
Default Paranoia or real effect?

On Sun, 11 Mar 2018 06:22:22 -0700 (PDT), "R. Mark Clayton"
wrote:

On Sunday, 11 March 2018 13:11:25 UTC, Jim Lesurf wrote:
In article , R.
Mark Clayton wrote:
We are after all in a very strong signal area here, and I'd have
thought it most unlikely that a properly installed aerial would have
this problem, which leaves either paranoia or a faulty installation.

Brian


Perhaps s/he has Freesat and is very close to the airport. Can't see a
mechanism otherwise.


RX being overloaded by some signals from the plane adding to the "strong"
ones from Freeview? i.e. matter of an RX that accepts and is overloaded by
out of band input at a high power level?


Faintly possible, but AFAIK the only big output from a plane is ATC in AM VHF [for now].


Is there any possibility of Freeview sugnals being reflected off the
plane at sufficient strength to interfere with the direct signal?

I suppose that would need a badly positioned aerial so that its
reception of the direct signal was poor.

--
Peter Duncanson
(in uk.tech.digital-tv)
  #7  
Old March 11th 18, 02:11 PM posted to uk.tech.digital-tv
Brian-Gaff
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Posts: 576
Default Paranoia or real effect?

This is Kingston upon Thames.
However, I wondered if maybe its possible to somehow tune into the channel
on a scanner and listen for the usual flutter on the signal as its really
just multipath cancelling or adding to the signal as the plane reflection
moves.
Brian

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"R. Mark Clayton" wrote in message
...
On Sunday, 11 March 2018 11:07:04 UTC, Brian Gaff wrote:
I was talking to somebody a week or so back who swears their freeview
goes
blacky and stutters whenever a plane from Heathrow goes over.


In Yorkshire.

Now in the good old analogue days you could detect aircraft flutter
quite
easily, how would you go about it on a digital system. I did not rise to
the
bait of suggesting I go around as to be honest there would be little I
could
do.

We are after all in a very strong signal area here, and I'd have thought
it
most unlikely that a properly installed aerial would have this problem,
which leaves either paranoia or a faulty installation.

Brian


Perhaps s/he has Freesat and is very close to the airport. Can't see a
mechanism otherwise.




  #8  
Old March 11th 18, 02:37 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
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Posts: 573
Default Paranoia or real effect?

Brian-Gaff wrote:

This is Kingston upon Thames.


# On pirate satellite ...
  #9  
Old March 11th 18, 03:44 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 2,448
Default Paranoia or real effect?

On 11/03/2018 11:07, Brian Gaff wrote:
I was talking to somebody a week or so back who swears their freeview goes
blacky and stutters whenever a plane from Heathrow goes over.
Now in the good old analogue days you could detect aircraft flutter quite
easily, how would you go about it on a digital system. I did not rise to the
bait of suggesting I go around as to be honest there would be little I could
do.

We are after all in a very strong signal area here, and I'd have thought it
most unlikely that a properly installed aerial would have this problem,
which leaves either paranoia or a faulty installation.

Brian

Reflected signals from rapidly moving wind turbine blades cause
cancellation and reinforcement effects that can put deep notches in a
mux. The notch will move rapidly across the mux. This can confuse some
TV sets, but not others. AGC inadequacies perhaps?
The fault is most likely to be seen when the turbine is slightly to one
side of the direct signal path, because in that case the receiving
aerial's forward lobe will include the turbine.
In the case of aeroplane reflections, a horizontally polarised TV
aerial, especially a log periodic, will have a forward lobe that
includes a lot of sky above the transmitter direction. A plane in that
area, if flying fairly low, could well have a surface with the angle of
incidence and reflection such that a strong signal might enter the TV
aerial.
I've never seen the fault though with digital TV, but I saw it lots of
times in the analogue days. Going even further back in time it used to
be a real bugger with BI TV.

Bill
  #10  
Old March 11th 18, 03:55 PM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,326
Default Paranoia or real effect?

In article , Bill Wright
wrote:
Reflected signals from rapidly moving wind turbine blades cause
cancellation and reinforcement effects that can put deep notches in a
mux.


I was wondering about the doppler from the plane's velocity. But you remind
me that the fan blades might also generate quite a lot of doppler on the
reflections. But I've not worked out the velocity needed to shift each
subcarrier by the difference in frequency between subcarriers.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa...o/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

 




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