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> Help >About UK Free TV >About UK Free TV

Improvements to Freeview transmission mode information

Following the changes to the commercial multiplexes that are now being rolled out over the main 80 transmitters, I have improved the information shown on the site.

Following the changes to the commercial multiplexes that are no
Published on by on UK Free TV

On each transmitter information page, there is a three-line description for each multiplex that lists the configuration used.

The first example shown here shows the new mode being used for the commercial multiplexes:



64QAM shows the number of "symbols" that are transmitted within each subcarrier, in effect in 8x8 positions. 8K is the number of subcarriers (which is actually 6817) used within the 8MHz UHF signal. 3/4 (three quarters, or 0.75) in this example is the amount of "forward error correction" used.

The second line shows the bitrates provided - in this example 27.1 megabits (million bits) per second.

The third line indicates the transmission standard used - DVB-T and the type of video encoding used, in this case MPEG-2.

The second example is from the Winter Hill transmitter, where a local television multiplex is broadcast:



Here the QSPK is a 2x2 position system, and results in only 6.0 megabits per second.

The third example shows the standard post-switchover configuration for the public service transmitters.



PSB1 and PSB2 use 64QAM, 8K (6817) but with forward error correction of 2/3 (two thirds, or 0.67). The use of this form of error correction provides 24.1 megabits per second.

PSB3 is used for Freeview HD, this showing on the third line as DVB-T2 MPEG4. DVB-T2 is a more advanced transmission system, with a number of enhancements over DVB-T. MPEG4 is also a newer, more efficient video encoding system.

The use of a 256QAM (16x16) symbol positions and 32KE (that's 27841) subcarriers results in a broadcast of 40.2 megabits per second.

The final example is from Rowridge, a transmitter in a pre-switchover state:



The low power digital transmissions use 2K (1705) subcarriers with a 16QAM (4x4), which results in 18.1 megabits per second per multiplex.

Bitrate comparisons

Compared to pre-switchover multiplexes 1, B, C and D:

  • Pre-switchover 2 and A: 33% more
  • Post-switchover PSB1. PSB2: 33% more
  • Post-switchover PSB3: 122% more.
  • Local TV: 67% less
  • Post-switchover COMs after changes: 50% more.






Your comments: most recent posts are at the bottom

firstFirst comments prevEarlier comments  ◊ 

Your comments are always welcome. Please use the form below to add your thoughts or questions to this page. We will get back to you as soon as we can.

Dave Lindsay
Thursday 1 December 2011 10:58PM

Glanville Carleton: The reason for this is because your receiver is picking up the signal from Belmont (whose principle service area is Lincolnshire and East Yorkshire) and it has decided to go with this instead of that from Sandy Heath.

What is the make and model of your receiver (TV or set-top box)? I will see if I can find the instructions for it and suggest how you might get it to do what you want it to do.


S
sheila macey
Sunday 15 July 2012 10:14AM

i have just purchased a panasonic television after having a freeview box but i cannot watch bbc 1 or 2 and some other channels what is the problem can youhelp please


J
jb38
Sunday 15 July 2012 1:47PM

sheila macey: With any question involving a reception issue its essential for a location to be given, and with this being in the form of a post code or at least one from nearby, as this will then enable the signal levels predicted for your area to be assessed.

Also, on the basis of what you have said it would be of assistance to know the model of Panasonic TV in question.


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