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Difference in Sig / Quality levels on BBC

  • 05-07-2021 3:16pm
    #1
    Registered Users Posts: 669 ✭✭✭


    What could be causing the difference in S & Q levels in transponders for BBC 1 NI HD and BBC 1 Scotland HD ?


Comments

  • Registered Users Posts: 20,137 ✭✭✭✭dxhound2005


    They are coming from different transponders.

    https://www.lyngsat.com/Astra-2E-2F-2G.html


  • Registered Users Posts: 13,977 ✭✭✭✭Johnboy1951


    mrtom wrote: »
    What could be causing the difference in S & Q levels in transponders for BBC 1 NI HD and BBC 1 Scotland HD ?

    Q is the same, so nothing to worry about it appears.

    They are on different transponders
    Scot on 11024H
    NI on 10847V


  • Registered Users Posts: 669 ✭✭✭mrtom


    Q is the same, so nothing to worry about it appears.

    They are on different transponders
    Scot on 11024H
    NI on 10847V


    Thanks, just to clear some concepts:
    Q = Strength of particular transponder signal to the dish and varies within parameters.
    L = Quality of signal between the dish & receiver, ie. cables and F connections. A fixed value I would imagine across all transponders.
    So why is the Level (L) value different here?


    Amiko Mini Combo Extra.


  • Registered Users Posts: 650 ✭✭✭lgs 4


    mrtom wrote: »
    Thanks, just to clear some concepts:
    Q = Strength of particular transponder signal to the dish and varies within parameters.
    L = Quality of signal between the dish & receiver, ie. cables and F connections. A fixed value I would imagine across all transponders.
    So why is the Link (L) value different here?


    Amiko Mini Combo Extra.

    You should be getting a steady stream across all transponders like below


  • Registered Users Posts: 669 ✭✭✭mrtom


    lgs 4 wrote: »
    You should be getting a steady stream across all transponders like below


    Appreciate your time in taking snaps. I see in your case the L value is almost identical. hmm....


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  • Registered Users Posts: 650 ✭✭✭lgs 4


    mrtom wrote: »
    Appreciate your time in taking snaps. I see in your case the L value is almost identical. hmm....

    How old is cabling from your dish to you're to box? I had a similar problem with low signal quality on a New Humax Freesat a few years back. The single-level would never rise above 60%. My cabling was 10 years old. I placed the cabling and the single level jumped from 60% to 85 %. What happens is the cabling shielding breaks down. The noise levels increase. That was Sky cabling installation.


  • Registered Users Posts: 669 ✭✭✭mrtom


    lgs 4 wrote: »
    How old is cabling from your dish to you're to box? I had a similar problem with low signal quality on a New Humax Freesat a few years back . The single-level would never rise above 60%. My cabling was 10 years old. I placed the cabling and the single level jumped from 60% to 85 % . What happens is the cabling shielding breaks down . The noise levels increase.


    Thanks for sharing your experience. But in my case why the difference between transponders I wonder ?


  • Registered Users Posts: 650 ✭✭✭lgs 4


    mrtom wrote: »
    Thanks for sharing your experience. But in my case why the difference between transponders I wonder?
    No problem
    It could be down to cabling. If you have another box and check levels on that box.


  • Registered Users Posts: 669 ✭✭✭mrtom


    lgs 4 wrote: »
    No problem
    It could be down to cabling. If you have another box and check levels on that box.


    Now that's helpfull, I can pipe it directly to the Sat tuner on the TV and compare.
    Neat diagnostic tip !


  • Registered Users Posts: 491 ✭✭Elvis Hammond


    mrtom wrote: »
    Thanks, just to clear some concepts:
    Q = Strength of particular transponder signal to the dish and varies within parameters.
    L = Quality of signal between the dish & receiver, ie. cables and F connections. A fixed value I would imagine across all transponders.
    So why is the Level (L) value different here?

    Is it not kind of obvious that Q is for quality, & L for level is the strength of the signal?

    Anyway, your receiver can't give a specific reading for the path between itself & the dish.

    If you're not having problems viewing, then there's no point worrying about it.


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  • Registered Users Posts: 5,329 ✭✭✭swoofer


    If you look closely one is vertical and the other horizontal. This means the lnb is ever so slightly off either the skew or the focal length. It’s adjusted but you need to check each one, so if h goes up v may go down. Focal length is distance of lnb to centre of dish. Skew is the twist. Size of dish will compensate as well. BUT if signal is ok and no loss then it’s no big deal.


  • Registered Users Posts: 669 ✭✭✭mrtom


    swoofer wrote: »
    If you look closely one is vertical and the other horizontal. This means the lnb is ever so slightly off either the skew or the focal length. It’s adjusted but you need to check each one, so if h goes up v may go down. Focal length is distance of lnb to centre of dish. Skew is the twist. Size of dish will compensate as well. BUT if signal is ok and no loss then it’s no big deal.


    Good, dish is easy to access and tweak for optimum to confirm. Reception is fine and no to all, I wasn't worried just curious and a desire to learn.
    Thanks swoofer for the answer and all who chimed in!


  • Registered Users Posts: 586 ✭✭✭TAFKAlawhec


    Could be different reasons why the raw signal strength meter on a receiver shows a significant difference...

    * The two stations are broadcast from different satellites, NI is from Astra 2E while Scotland is from Astra 2G - 2E is slightly more eastern of Astra 2F & 2G though this usually wouldn't matter on the size of dish normally used for 28E reception in Ireland. However slight differences in the UK & Ireland spot beam on both birds might lead to small differences.

    * As swoffer has pointed out, they are opposing polarities - there may be inconsistencies in the LNB manufactured where the skewing isn't "dead on" to get the best out of both horizontal and vertical polarised signals and sometimes a compromise position needs to be found, not to mention there may be slight discrepancies between the transmitted polarities from each satellite. This is rarely needed in Ireland due to the power of the signals being received, but there is no harm trying.

    * The signal the BBC Scotland transponder that is being downconverted to by the LNB to be sent to the receiver is a higher frequency than that for the NI transponder - if the coax is quite a long run (or isn't great quality, or both) then this could show up as a lower signal strength received on the receiver - however frequencies higher than this should also show up as having lower signal strength (in theory as long as they're on the same beam/footprint).

    * Like with terrestrial transmissions, even if the transmissions came from the same satellite and used the same beam, same radiated power, same polarisation etc. (which they don't in this case) more often than not they will have at least slightly different signal levels when they reach the LNB thanks to the path the signal takes where atmospheric changes, weather etc. all have a varying effect on slightly different frequencies.

    * The following doesn't apply to this scenario, but is well worth remembering for other possible situations, is that the signal from the satellite itself or the frequency the LNB downconverts to for the receiver's tuner to pick up may be subject to interference. In the former case it is most likely a case of co-channel interference - some transponders from 28E in some locations may be affected by transmissions on the same frequency & polarisation from the Badr 4 satellite just 2 degrees away (though none of the BBC ones) even though the signals from Badr 4 in Ireland are weaker than those from 28E, while in the latter case terrestrial or local signals from around 950 MHz to 2100 MHz can affect reception of certain transponders especially if the interfering signal is very strong, things like DECT cordless phones, mobile telephone BTS's, amateur radio etc. which highlights the importance of using good, well shielded coax from the LNB to receiver to keep external interference out. However, in both these cases there should not be a problem with the signal level but the quality which would go down, which is why it shouldn't apply here.

    * Finally, it's possible though unlikely that the transponder receiving the Scotland channel is being received too strongly, densing the tuner in the receiver - however that would normally also affect the quality rating as well, and even with the signal strengths received in Ireland you'd have to be using a monster size of a dish for that to be a plausible possibility.

    All in all, if you're regularly watching the Scottish channel then it might be worth having a look at improving the signal strength at the dish but unless you're signal is cutting out during moderate rainfall, it's probably not going to be worthwhile.


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