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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.

4G possible effects



 
 
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  #1  
Old February 12th 15, 03:31 PM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Default 4G possible effects

Not sure yet, but I've encountered problems with our Ch60- mux reception
this afternoon (on three different receivers). And two weeks ago I saw that
the base station top-end nearby was being changed. Since then I have
detected some '4G' signals. (The base station is about 400 m away in about
the same direction as the TV TXs.)

I've taken some fresh spectra and will do some checking and then report if
this is 4G or not. FWIW The "ch60" filter AT800 sent to me didn't fix the
problem. But its possible its something else. Or a combination with, say,
the TV muxes being low due to atmospheric conditions. Know more once I've
had more time to check things.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

  #2  
Old February 12th 15, 04:28 PM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Default 4G possible effects

On 12 Feb, wrote:
Know more once I've had more time to check things.


Looks like a textbook case.

http://jcgl.orpheusweb.co.uk/temp/4Goverload.png

Shows the output from the UHF downlead with and without the AT800 'C60'
filter. This doesn't fix the interference because the 4G is overloading the
distribution amp in the loft. Which then throws intermod sideband noise
across a lot of the band. Putting the filter in the room download reduced
the 4G signal but leaves the intermod garbage sprayed across the band.

Next challenge will be if I can manage to get up a ladder into the loft in
the next day or two and attach the C60 filter in *front* of the
distribution amp. Then see if that fixes the problem or I need to also
add/alter something else.

My antenna is in the *loft* so heaven help anyone nearer to the base
station who has an amp on an external antenna!

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

  #3  
Old February 12th 15, 08:12 PM posted to uk.tech.digital-tv
Bill Wright[_2_]
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Posts: 9,381
Default 4G possible effects

Jim Lesurf wrote:
On 12 Feb, wrote:
Know more once I've had more time to check things.


Looks like a textbook case.

http://jcgl.orpheusweb.co.uk/temp/4Goverload.png

Shows the output from the UHF downlead with and without the AT800 'C60'
filter. This doesn't fix the interference because the 4G is overloading the
distribution amp in the loft. Which then throws intermod sideband noise
across a lot of the band. Putting the filter in the room download reduced
the 4G signal but leaves the intermod garbage sprayed across the band.

Next challenge will be if I can manage to get up a ladder into the loft in
the next day or two and attach the C60 filter in *front* of the
distribution amp. Then see if that fixes the problem or I need to also
add/alter something else.

My antenna is in the *loft* so heaven help anyone nearer to the base
station who has an amp on an external antenna!

Jim


It worries me that the muxes are so uneven and irregular across their
width. This is bound to increase the susceptibility to interference. You
want to get a decent aerial fixed up outside.

The dist amp must be perilously close to overload if 4G only 10dB above
the muxes is having such an effect. But see above!

Your filter is working, but wait til signals appear just 2MHz above ch 60!

Bill
  #4  
Old February 12th 15, 08:22 PM posted to uk.tech.digital-tv
Graham.[_5_]
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Default 4G possible effects


Adam is looking for thou in uk.d-i-y



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Graham.

%Profound_observation%
  #5  
Old February 12th 15, 08:50 PM posted to uk.tech.digital-tv
Andy Burns[_9_]
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Posts: 389
Default 4G possible effects

Bill Wright wrote:

It worries me that the muxes are so uneven and irregular across their
width.


The noise in the "white spaces" between the muxes is noticeably higher
than in the scan Jim posted in May.


  #6  
Old February 12th 15, 10:00 PM posted to uk.tech.digital-tv
[email protected]
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Default 4G possible effects

On Thu, 12 Feb 2015 21:50:51 +0000, Andy Burns
wrote:

Bill Wright wrote:

It worries me that the muxes are so uneven and irregular across their
width.


The noise in the "white spaces" between the muxes is noticeably higher
than in the scan Jim posted in May.

Almost certainly that's due to intermodulation between the 4G
transmissions and the TV signals, mixing at any and every convenient
nonlinear point.
  #9  
Old February 13th 15, 11:05 AM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,326
Default 4G possible effects

In article ,
wrote:
On Thu, 12 Feb 2015 21:50:51 +0000, Andy Burns
wrote:


Bill Wright wrote:

It worries me that the muxes are so uneven and irregular across their
width.


The noise in the "white spaces" between the muxes is noticeably higher
than in the scan Jim posted in May.

Almost certainly that's due to intermodulation between the 4G
transmissions and the TV signals, mixing at any and every convenient
nonlinear point.


That's what I'm assuming at present. However a point to add is that the
noise floor of the *measurement* is slighly higher than usual as I couldn't
apply much post mixer gain without risking overloading the measurement as
the 4G level is so high.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

  #10  
Old February 13th 15, 11:02 AM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
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Posts: 4,326
Default 4G possible effects

In article , Bill Wright
wrote:
Jim Lesurf wrote:



It worries me that the muxes are so uneven and irregular across their
width. This is bound to increase the susceptibility to interference. You
want to get a decent aerial fixed up outside.



....which would presumably pick up even more 4G. 8-]

The dist amp must be perilously close to overload if 4G only 10dB above
the muxes is having such an effect. But see above!


Yes, it seems clearly to be overloading. All being well I'll be up a ladder
this afternoon to try putting the AT800 filter *before* the distribution
amp. With luck that'll cut down the intermod 'wings' and improve the
situation. Know more later. All I have to do is survive being up a ladder
on Friday 13th!

Your filter is working, but wait til signals appear just 2MHz above ch
60!


The filter does seem to have quite a distinct 'notch' above ch60. I did a
proper measurement of it this morning but not yet worked out the results.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

 




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