My Humax Forum » Freeview HD » HDR 1800T, 2000T

Aerials, Splitters, and SFN.

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    Johnh510

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    Further to the drift on the "unacceptable hard drive noise" thread -

    The metal bodied splitter from Screwfix was recommended as the fix for loss of RF feed through on the 2000T, as that loss is another irritation/shortcoming of that PVR. (Hard drive noise being top of the list, and I won't include a third irritation here

    Consequential loss of COM 7/8 is another story - I got a new aerial as my signal strength is not the best: Labgear 450T. This aerial is NOT intended to pass above channel 60 (4G and all that), so that may be off its best gain by channels 55/56.

    I have a suspicion that the SFN is being "tried out" carrying services which won't cause too much outrage when there are problems, to assess and modify if necessary - a work in progress.

    | Tue 1 May 2018 9:48:33 #1 |
  2. grahamlthompson

    grahamlthompson

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    What does the DTG reception predictor say for your location ? Use the detailed view option.

    http://www.digitaluk.co.uk/operations/about_the_coverage_checker

    | Tue 1 May 2018 10:04:14 #2 |
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    Johnh510

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    Looks like this, assuming tabs/spaces copy OK.

    BBC A 43 99 100

    D3&4 46 99 100

    BBC B HD 40+ 99 100

    SDN 42 100 100

    ARQ A 45 100 100

    ARQ B 39+ 100 100

    COM7 HD 55 98 100

    COM8 HD 56 100 100

    I suppose at this point I should say my signal strength problem is due to local obstructions. Mostly trees, but other stuff too.

    | Tue 1 May 2018 12:07:48 #3 |
  4. grahamlthompson

    grahamlthompson

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    Johnh510 - 29 minutes ago  » 
    Looks like this, assuming tabs/spaces copy OK.
    BBC A 43 99 100
    D3&4 46 99 100
    BBC B HD 40+ 99 100
    SDN 42 100 100
    ARQ A 45 100 100
    ARQ B 39+ 100 100
    COM7 HD 55 98 100
    COM8 HD 56 100 100
    I suppose at this point I should say my signal strength problem is due to local obstructions. Mostly trees, but other stuff too.

    Have you considered your signal strength is just too high. I would have used a log periodic with levels like that. Signal clipping can produce low indicated levels when in fact the signal is too high for a sensitive tuner to cope with.

    Try fitting a variable attenuator.

    | Tue 1 May 2018 12:40:16 #4 |
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    Johnh510

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    The predicted signal strength doesn't allow for the following local factors:

    My aerial is in the loft. It does "look" through the PVC fascia boards above a "Dormer" window, rather than the tiles, but there is some signal strength loss there compared with being outside.

    There are two trees which were planted 30 odd years ago and they have grown into the line of sight to the transmitter. They are not mine and the owners might get a bit funny about me getting them chopped down. Either side of these trees there are much bigger mature/old trees.

    A few hundred metres beyond all that there is a 132kv transmission line and tower. There is a "window" to the left of the tower and below the slung cables towards the transmitter. The position in the loft is one of the few places which have a sensible view through that gap towards the transmitter.

    All in all, you wouldn't start from here if you really wanted to watch terrestrial TV.
    I used to use a Humax Foxsat, but the trees at the back of the house grew and got in the way.... perhaps it's time to move house.

    | Tue 1 May 2018 13:48:10 #5 |
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    Faust

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    I have been conducting an experiment today to see if I could improve on our current reception in relation to channels 55 & 56.

    I have been using pass through via our BT Youview box having previously used a passive splitter (the cheap plastic Maplins special). The splitter just wasn't working following the retune in March, it was simply knocking the signal down too far.

    Given the very reasonable price of the metal two-way splitter Graham recommended previously https://www.screwfix.com/p/labgear-19132r-s-2-way-metal-t-splitter/44534 I decided to give one of these a go.

    As expected the splitter did drop the signal, though nowhere near as much as the previous plastic splitter had done. What has amazed me though is despite the signal strength dropping down to around 53% on channel 55 and 45% on channel 56 the signal quality across both has shot up to 100% with both channels appearing 'steady'. I have no explanation for this.

    As a side note I also conducted another experiment. I tried a manual tune of the channels my previous aerial had been tuned to i.e. Fenton (I'm now on Sutton Coldfield). Those channels are in the 20s except COM 7 and 8 which is the same as SC i.e. 55 & 56. The only mux the TV could find was the one for BBC1 (channel 22 I think). This came in pretty strong and pushed the SC BBC 1 mux up into the 800s.

    | Tue 1 May 2018 14:21:00 #6 |
  7. grahamlthompson

    grahamlthompson

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    Johnh510 - 2 hours ago  » 
    The predicted signal strength doesn't allow for the following local factors:
    My aerial is in the loft. It does "look" through the PVC fascia boards above a "Dormer" window, rather than the tiles, but there is some signal strength loss there compared with being outside.
    There are two trees which were planted 30 odd years ago and they have grown into the line of sight to the transmitter. They are not mine and the owners might get a bit funny about me getting them chopped down.

    Either side of these trees there are much bigger mature/old trees.
    A few hundred metres beyond all that there is a 132kv transmission line and tower. There is a "window" to the left of the tower and below the slung cables towards the transmitter. The position in the loft is one of the few places which have a sensible view through that gap towards the transmitter.
    All in all, you wouldn't start from here if you really wanted to watch terrestrial TV.
    I used to use a Humax Foxsat, but the trees at the back of the house grew and got in the way.... perhaps it's time to move house.

    The 132kV line is very unlikely to be an issue.

    If it was 400kV or 275kV then carbonised grease nodules (the conductors are greased especially when steel cored aluminium is can produce corona discharge which will be visible in dark and wet conditions and make the line very noisy. Corona discharges may well create interference in the UHF band. The cure is for National Grid to clean the external surface of the conductors. As the line is 132kV it will belong to a different company.

    Trees are a different situation, trees normally create issues in windy conditions. As the branches move they create a form of multipath reception that causes the signal to break up, usually easily identified by large gusts. I have this situation which precludes me using Sutton Coldfield in the summer months.

    I have a log36 in my loft some 30 mls or so from the lower power Lark Stoke relay, it gives rock solid 100% quality, despite the worst mux only showing 40% signal.

    I still reckon the attenuator is worth a shot.

    Have you tried different locations for the aerial in the loft ? Even a small move can make a big difference.

    | Tue 1 May 2018 16:50:18 #7 |
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    Martin Liddle

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    grahamlthompson - 4 hours ago  » 
    Have you considered your signal strength is just too high.

    The quoted numbers are not the actual signal strength but the numbers you requested from the DTG reception predictor.

    | Tue 1 May 2018 16:50:57 #8 |
  9. grahamlthompson

    grahamlthompson

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    Martin Liddle - 4 minutes ago  » 

    grahamlthompson - 4 hours ago  » 
    Have you considered your signal strength is just too high.

    The quoted numbers are not the actual signal strength but the numbers you requested from the DTG reception predictor.

    I realised that, they simply indicated that the high gain aerial used by the OP created the possibility that the signal is just too high. I doubt the PVC has much in the way of signal attenuation.

    | Tue 1 May 2018 16:57:26 #9 |
  10. grahamlthompson

    grahamlthompson

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    Faust - 2 hours ago  » 
    I have been conducting an experiment today to see if I could improve on our current reception in relation to channels 55 & 56.
    I have been using pass through via our BT Youview box having previously used a passive splitter (the cheap plastic Maplins special). The splitter just wasn't working following the retune in March, it was simply knocking the signal down too far.
    Given the very reasonable price of the metal two-way splitter Graham recommended previously https://www.screwfix.com/p/labgear-19132r-s-2-way-metal-t-splitter/44534 I decided to give one of these a go.
    As expected the splitter did drop the signal, though nowhere near as much as the previous plastic splitter had done. What has amazed me though is despite the signal strength dropping down to around 53% on channel 55 and 45% on channel 56 the signal quality across both has shot up to 100% with both channels appearing 'steady'. I have no explanation for this.
    As a side note I also conducted another experiment. I tried a manual tune of the channels my previous aerial had been tuned to i.e. Fenton (I'm now on Sutton Coldfield). Those channels are in the 20s except COM 7 and 8 which is the same as SC i.e. 55 & 56. The only mux the TV could find was the one for BBC1 (channel 22 I think). This came in pretty strong and pushed the SC BBC 1 mux up into the 800s.

    Those cheap splitters are just rubbish. Imagine the 4dB or so of attenuation has resolved the issue.

    | Tue 1 May 2018 16:59:14 #10 |

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