A Sky, cable and digital tv forum. Digital TV Banter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » Digital TV Banter forum » Digital TV Newsgroups » uk.tech.digital-tv (Digital TV - General)
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

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.

2018 Q1 700 MHz Clearance details



 
 
Thread Tools Display Modes
  #111  
Old December 4th 17, 02:34 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,095
Default 2018 Q1 700 MHz Clearance details

On 04/12/2017 14:22, Mark Carver wrote:

I remember going to a talk at the Royal Television Society about
digital TV, just after OnDigital had launched, and the lecturer said
that it had been designed in that the overall spectrum was to appear
as random and noise-like as possible in case of interference with
analogue TV.


That's nonsense, (C)OFDM is a modulation scheme that was adopted for
DVB-T, but it's used in a multitude of applications from ADSL, to WiFi,
to mobile phones, wireless microphones etc etc.....


Lecturers are not immunune from talking ********.

I remember this, in Geology. "I'm obliged to teach you about plate
tectonics (as they are calling their absurd theory) but let me tell you
now I don't believe a word of it."

And this in Divinity. "You deny the word of God. You'll be taught the
error of your ways within ten years, when you start to lose your hair.
That will be God's punishment." I kid you not.

Bill
  #112  
Old December 4th 17, 04:14 PM posted to uk.tech.digital-tv
Jim Lesurf[_2_]
external usenet poster
 
Posts: 4,228
Default 2018 Q1 700 MHz Clearance details

In article , Mark Carver
wrote:
I remember going to a talk at the Royal Television Society about
digital TV, just after OnDigital had launched, and the lecturer said
that it had been designed in that the overall spectrum was to appear
as random and noise-like as possible in case of interference with
analogue TV.


That's nonsense, (C)OFDM is a modulation scheme that was adopted for
DVB-T, but it's used in a multitude of applications from ADSL, to WiFi,
to mobile phones, wireless microphones etc etc.....



FWIW one of the basics of Information Theory is that 'efficient' modulation
systems tend to have stats which mimic random noise. Departures from this
tend to be for reasons other than efficient data use.

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
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

  #113  
Old December 4th 17, 06:17 PM posted to uk.tech.digital-tv
NY
external usenet poster
 
Posts: 1,232
Default 2018 Q1 700 MHz Clearance details

"Jim Lesurf" wrote in message
...
In article , Mark Carver
wrote:
I remember going to a talk at the Royal Television Society about
digital TV, just after OnDigital had launched, and the lecturer said
that it had been designed in that the overall spectrum was to appear
as random and noise-like as possible in case of interference with
analogue TV.


That's nonsense, (C)OFDM is a modulation scheme that was adopted for
DVB-T, but it's used in a multitude of applications from ADSL, to WiFi,
to mobile phones, wireless microphones etc etc.....



FWIW one of the basics of Information Theory is that 'efficient'
modulation
systems tend to have stats which mimic random noise. Departures from this
tend to be for reasons other than efficient data use.


It's weird. I've have distinct memories of a block diagram of the encoding
process from camera to UHF transmitter, which has a block which was a pseudo
random signal generator to convert the signal to look as random as possible
so as to avoid any patterning on analogue. And this was somewhere other than
in this lecture, and it wasn't Wikipedia. And yet I can''t find anything
about it now.

Maybe someone spouted some ******** in the early days and it became
"official" in other documents :-)

  #114  
Old December 4th 17, 06:49 PM posted to uk.tech.digital-tv
Mark Carver
external usenet poster
 
Posts: 7,594
Default 2018 Q1 700 MHz Clearance details

On 04/12/2017 18:17, NY wrote:

It's weird. I've have distinct memories of a block diagram of the
encoding process from camera to UHF transmitter, which has a block which
was a pseudo random signal generator to convert the signal to look as
random as possible so as to avoid any patterning on analogue. And this
was somewhere other than in this lecture, and it wasn't Wikipedia. And
yet I can''t find anything about it now.


Ah ! The BBC and NTL/ITC did conduct test transmissions of 'fake' DTT
signals to determine what the effect and tolerable levels of DTT on
analogue reception might be. I recall seeing those sort of diagrams.

--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #115  
Old December 4th 17, 08:40 PM posted to uk.tech.digital-tv
Ian Jackson[_7_]
external usenet poster
 
Posts: 83
Default 2018 Q1 700 MHz Clearance details

In message , Bill Wright
writes
On 04/12/2017 10:07, Scott wrote:

I can't remember the details, but the re-tuners moved all the VCRs in
Sheffield onto a channel that became a DTT mux not long after.

This sounds feasible. As far as I can see, Channel 5 started in 1997
and ONdigital in 1998.
Would the fairly low-powered (as they were then) digital signals
disrupt the analogue link between VCR and TV?


Yes they usually did. It looked like weak signal because it lifted the
noise floor on the channel. Could it have been ch39? I can't remember.

Bill


QAM was being introduced on cable TV systems long before they started
using it for off-air transmissions. I think it's simply fortuitous that
it looks like noise when under an analogue signal. Another advantage is
that the power level of the off-air digital transmissions is generally
much lower than the 'old' analogue (10 or 16dB?).
--
Ian
  #116  
Old December 4th 17, 09:24 PM posted to uk.tech.digital-tv
Woody[_5_]
external usenet poster
 
Posts: 1,802
Default 2018 Q1 700 MHz Clearance details


"Ian Jackson" wrote in message
...
In message , Bill Wright
writes
On 04/12/2017 10:07, Scott wrote:

I can't remember the details, but the re-tuners moved all the
VCRs in
Sheffield onto a channel that became a DTT mux not long after.

This sounds feasible. As far as I can see, Channel 5 started in
1997
and ONdigital in 1998.
Would the fairly low-powered (as they were then) digital signals
disrupt the analogue link between VCR and TV?


Yes they usually did. It looked like weak signal because it lifted
the noise floor on the channel. Could it have been ch39? I can't
remember.

Bill


QAM was being introduced on cable TV systems long before they
started using it for off-air transmissions. I think it's simply
fortuitous that it looks like noise when under an analogue signal.
Another advantage is that the power level of the off-air digital
transmissions is generally much lower than the 'old' analogue (10 or
16dB?).
--


Well, yes and no.

The erp of DTTV is usually 7dB lower than the 'quoted' power of
analogue, however this is largely due to the method of measurement.
Analogue signals were measured at peak sync which was typically 10dB
above the average level of video, but the average level of a COFDM is
pretty constant to a power meter so in practice the actual - shall we
call it 'usable' - power level is 3dB higher than in analogue days.

Also don't overlook the fact that DTTV receivers are generally of the
order of 20dB or greater more sensitive than analogue.



--
Woody

harrogate3 at ntlworld dot com


  #117  
Old December 5th 17, 01:20 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,095
Default 2018 Q1 700 MHz Clearance details

On 04/12/2017 21:24, Woody wrote:

Also don't overlook the fact that DTTV receivers are generally of the
order of 20dB or greater more sensitive than analogue.


They are not more intrinsically sensitive; it's the fact that DTT can
function with a much lower signal to noise ratio.

Bill
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT. The time now is 06:46 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.SEO by vBSEO 2.4.0
Copyright 2004-2017 Digital TV Banter.
The comments are property of their posters.