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Saorview Mux2 on 198.5 Mhz VHF Dublin (7Mhz bandwidth)

  • 28-08-2016 04:46PM
    #1
    Boggy
    Registered Users, Registered Users 2 Posts: 21 ✭


    Anyone else picking up this mux, I can see that the data rate is different 23.75Mbps compared to the normal mux (24.14) which has 8Mhz bandwidth


Comments

  • #2
    Thurston?
    Closed Accounts Posts: 2,278 ✭✭✭Thurston?


    Not near Dublin myself but remember around the time of switchover, there were reports here of a mux like that running.


  • #3
    Boggy
    Registered Users, Registered Users 2 Posts: 21 ✭Boggy


    I'm in Rathfarnham using an amplified attic aerial, signal isn't as strong as Three Rock.

    Looks like an FEC of 3/4 is being used instead of an FEC of 2/3 to increase the data rate which may make it harder to receive.


  • #4
    The Cush
    Registered Users, Registered Users 2, Paid Member Posts: 16,493 ✭✭✭✭The Cush


    That bitrate, 23.75Mbps, matches the parameters used in the previous VHF tests which were reported here into 2013, probably from the Donnybrook Tower.

    VHF Ch. 8 (7 MHz channel) 198.5Mhz (c/f)
    8K, 64-QAM, GI 1/32, FEC 3/4

    s59wna.jpg

    Probably occasional testing of installed equipment as they have said in recent times they have no plans to transmit DTT in the VHF band.
    RTÉ believes that VHF spectrum is not a viable alternative for even current digital terrestrial television requirements. It would require an entirely new broadcast network, replacement antennas for all viewers, and a reduced amount of content with no facility for further development. Furthermore, there are no viable alternative or converged technology solutions that can deliver public service free-to-air digital terrestrial television comparable to DVB technology likely to emerge in the medium term.


  • #5
    PureIsle
    Registered Users, Registered Users 2 Posts: 172 ✭✭PureIsle


    Boggy wrote: »
    Anyone else picking up this mux, I can see that the data rate is different 23.75Mbps compared to the normal mux (24.14) which has 8Mhz bandwidth

    I have had three muxes showing from Maghera for a long time using tvheadend. I thought the third one was related to over the air information.
    In truth never gave it much thought.


  • #6
    Thurston?
    Closed Accounts Posts: 2,278 ✭✭✭Thurston?


    PureIsle wrote: »
    I have had three muxes showing from Maghera for a long time using tvheadend. I thought the third one was related to over the air information.

    Is the 3rd definitely from Maghera, not just one of the 'regular' muxes being picked up from another transmitter?

    What frequency is it on?


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  • #7
    The Cush
    Registered Users, Registered Users 2, Paid Member Posts: 16,493 ✭✭✭✭The Cush


    I remember there was some issue a few years ago where a mux was being identified at 198.5 MHz but appeared to have been a DVB-T software issue identifying the UHF existing mux on a different frequency.


  • #8
    PureIsle
    Registered Users, Registered Users 2 Posts: 172 ✭✭PureIsle


    Here is what I see tonight .... https:// is missing from beginning

    dl.dropboxusercontent.com/u/5838889/tvheadend-maghera.png


  • #9
    Gerry Wicklow
    Registered Users, Registered Users 2 Posts: 4,585 ✭✭✭Gerry Wicklow


    AFAIK when you do a network scan, RTÉ/2RN include the 198.5 freq in their listings. That Maghera scan tries the freq but is not getting any signal. However, I remember getting some channels which seemed to be on 198.5 in Dublin several years back. I even posted a screen grab as others were sceptical at the time.


  • #10
    Gerry Wicklow
    Registered Users, Registered Users 2 Posts: 4,585 ✭✭✭Gerry Wicklow


    Found it.


  • #11
    The Cush
    Registered Users, Registered Users 2, Paid Member Posts: 16,493 ✭✭✭✭The Cush


    PureIsle wrote: »
    Here is what I see tonight .... https:// is missing from beginning

    dl.dropboxusercontent.com/u/5838889/tvheadend-maghera.png

    Transport Stream ID is the same a UHF Mux1, my guess it's a software issue.


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  • #12
    The Cush
    Registered Users, Registered Users 2, Paid Member Posts: 16,493 ✭✭✭✭The Cush


    Gerry Wicklow wrote: »
    Found it.

    Yes I remember that post, the difference between that and the issue at Maghera is that particular VHF mux from Donnybrook(?) actually appears to carry content with a mux capacity of 23.75 Mbps as posted in the first post.


  • #13
    Gerry Wicklow
    Registered Users, Registered Users 2 Posts: 4,585 ✭✭✭Gerry Wicklow


    I'll have a look again next time I'm in the big smoke.;)


  • #14
    marno21
    Moderators, Science, Health & Environment Moderators Posts: 14,964 Mod ✭✭✭✭marno21


    Any particular reason they are broadcasting a VHF mux, even under test conditions, when they state that they have absolutely no intention of broadcasting on the VHF Band III spectrum?

    Money spent on this wastage would be much better invested in FM/DTT relays in parts of the country that struggle for reception.


  • #15
    Gerry Wicklow
    Registered Users, Registered Users 2 Posts: 4,585 ✭✭✭Gerry Wicklow


    marno21 wrote: »
    Any particular reason they are broadcasting a VHF mux, even under test conditions, when they state that they have absolutely no intention of broadcasting on the VHF Band III spectrum?

    Money spent on this wastage would be much better invested in FM/DTT relays in parts of the country that struggle for reception.
    Presumably the same 'logic' that lets them waste bandwidth on test cards instead of proper HD resolution. :mad:


  • #16
    STB.
    Registered Users, Registered Users 2 Posts: 5,380 ✭✭✭STB.


    The Cush wrote: »
    That bitrate, 23.75Mbps, matches the parameters used in the previous VHF tests which were reported here into 2013, probably from the Donnybrook Tower.

    VHF Ch. 8 (7 MHz channel) 198.5Mhz (c/f)
    8K, 64-QAM, GI 1/32, FEC 3/4

    Probably occasional testing of installed equipment as they have said in recent times they have no plans to transmit DTT in the VHF band.

    I also read a PAT test that someone recorded of an 8MHZ channel at that VHF frequency, some time back.

    DVB-T Frequency 198.500 MHz Bandwidth: 8 MHz Constellation: 64-QAM Hierarchy: non-hierarchical, native interleaver
    Guard Interval 1/32 Code Rate: 2/3

    They have 5 VHF frequencies defined in the Frequency Descriptor list.

    Terrestrial: 177.500 MHz
    Terrestrial: 184.500 MHz
    Terrestrial: 191.500 MHz
    Terrestrial: 198.500 MHz
    Terrestrial: 205.500 MHz


  • #17
    The Cush
    Registered Users, Registered Users 2, Paid Member Posts: 16,493 ✭✭✭✭The Cush


    STB. wrote: »
    I also read a PAT test that someone recorded of an 8MHZ channel at that VHF frequency, some time back.

    DVB-T Frequency 198.500 MHz Bandwidth: 8 MHz Constellation: 64-QAM Hierarchy: non-hierarchical, native interleaver
    Guard Interval 1/32 Code Rate: 2/3

    Could be a reason that some DVB-T software is misidentifying a "third" VHF mux at 198.5 MHz like the one mentioned on the previous page at Maghera using tvheadend. It also came up in discussion here a few years ago.

    The Dublin one appeares to be different as it carried test content, as we can see from Gerry's post, at a time where the single national mux was fully operational and days away from ASO. The mux capacity info posted by Boggy matches the parameters posted here back in 2012. All of this on a VHF DTT frequency allocated to Kippure, Three Rock and Greystones. I guess we never know for sure why this is happening.


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