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Evening BBC reception problems

Discussion in 'Audio Visual' started by davecooper, 30 May 2017.

  1. davecooper

    davecooper

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    I live in South Cumbria and have a fairly new terrestrial aerial pointed accurately at the Winter Hill transmitter near Bolton. Recently I have been having problems with receiving BBC channels in the evening. During the day, there are no reception problems although the signal strength does seem a bit low. However, in the evening, the signal starts to break up and gets worse over a period of about 10 to 15 minutes until the signal is lost altogether. However, during this time, all non BBC channels are ok as are BBC HD channels! The signal slowly comes back after perhaps an hour or so but I am at a loss to know what may be causing this. Any advice welcome.
     
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  3. Lucid

    Lucid

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    Who installed the aerial system; you or a recognised professional installer?

    Does the signal run through any cabling that was installed by the house builders?

    What type of aerial is it: a Yagi, a "wide band high gain" or a Log Periodic?

    Have you looked in to what other main transmitters also broadcast on ch50? e.g. Pontop Pike
     
  4. davecooper

    davecooper

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    It is a 48 element wideband high gain aerial. I ran new coax from my aerial socket to the roof and the aerial was then erected by a professional. He said that the signal strength was good at the time (around 18 months ago). In have not tried any other transmitter.
     
  5. bernardgreen

    bernardgreen

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    Possibly due to UHF skip ( Tropospheric propagation ) allowing signals from a distant transmitter to reach your aerial with sufficient strength to corrupt the signal of the channel carrying the missing programs.
     
  6. winston1

    winston1

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    No such thing as a 48 element aerial. You have been lied to and the lier has counted the elements 4 times. A quad cross type element is one not four. Those type of aerials are usually poorly made and cause troubles sooner or later. A true professional would not fit them.
     
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  8. davecooper

    davecooper

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    Ok, but only quoting what it says on the tin. Anyway, it looks as though signal strengths in general have dropped considerably since the aerial was first put up so a bit of investigation needed I think. In my area, this type of aerial seems to adorn 90% of properties.
     
  9. Lucid

    Lucid

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    bernardgreen has skipped ahead to where I was going to go with this. Your aerial is most likely picking up a second signal from another transmitter on the same channel (ch50) as your BBC reception from Winterhill. The transmitter up in Durham at Pontop Pike is the closest I can think of that would fit the bill.

    winston1 is correct when he says that the number of elements of your aerial has been overstated. Don't worry, it's widespread. It's this idea that a bigger number is somehow better; complete horse-crap of course, but it doesn't stop the marketing departments playing these games.

    The world and his dog has tried to cash in on selling aerials, and the wideband high gain seemed to be the "fits all" solution for anyone looking for an easy solution. After all, who wouldn't want an aerial the covers a really wide band and that seems to offer lots of gain, right? For lots of the UK this isn't a great aerial type. What's not made clear unless you do some research in to aerials is that this type is only "high gain" at the upper end of the frequency range.

    Ironically Winterhill is actually one of the few transmitters in the UK where this type of aerial used to be a good fit. I say 'used to be' because since the Government decided to sell of chunks of the TV transmission space to mobile phone operators for obscene piles of cash we've all had to endure what feels like endless rounds of retunes as the frequency distribution gets shuffled down the range and away from where 90% of the house aerials work best that are fitted to the homes in your area. Therefore the wideband high gain aerial is no longer the aerial of choice for the Winterhill transmitter.

    The other thing you find out about aerials if you start to study the topic is that they don't just pick up what they're pointing at. They also pick up from behind, and that's not good. The amount this happens varies with the aerial type. No prizes for guessing which aerials don't do so well in rejecting transmissions from behind.

    Finally, cable quality is important. The best cable isn't expensive, and it works out a hell of a lot cheaper than the budget stuff if it does a better job, lasts longer, and you don't end up having to replace it prematurely. The good stuff is Webro WF100. Acceptable alternatives are Triax TX100 and Labgear PF100. These are good because they're an all copper cable (no plastic mylar or cheaper aluminium or copper coated steel - CCS) and they get more of the aerial signal to the receiver because they have lower losses. The copper shielding (braid and metal foil) is much better at dealing with signal interference too. Bad cable (the stuff to avoid) is RG6, RG59 or anything sold as "low loss coax" but without any kind of technical detail.

    RG6 is often used by aerial installers looking to cut corners. It works out at roughly 18 pence per metre for a 100m roll. The same roll length in WF/TX/PF100 gives a price of around 40p/metre. Since the typical downlead from the aerial on the roof to the lounge TV requires about 15m of coax then the difference in price for that run is £3.30.... i.e. peanuts in the grand scheme of things.

    From experience out in the field sorting out people's aerial problems, I see three main problems with RG6. First, being a steel core with just a flash of copper for anti-corrosion the cable has a higher resistance so less of the signal makes it down to the receiver from the aerial. Second, the outer jacket is loose and it tends to go brittle due to UV and weathering quicker than with good cable. Third, when water does get in to the cable I've seen the aluminium shield braid disintegrate. This can cause intermittent signal loss.


    It's not all bad news. The fact that you're still getting the BBC HD channels is good. They're at the bottom end of the frequency range where your aerial doesn't work that efficiently, so that means there's enough signal strength in your area that you can use a Log Periodic aerial.

    What I would suggest is a change of aerial to one that is less prone to picking up from the Durham transmitter which is in the opposite direction to Winterhill. Buy a Group T Log Periodic aerial. It covers the whole channel band from c21 to c60. If your cable isn't all copper (WF100 or equivalent) then change that too. The aerial and cable should come in at less than £40.
     
    Last edited: 31 May 2017
  10. davecooper

    davecooper

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    When I ran the new aerial cable, I left the old one in as well and ran them to a double aerial socket in my living room, a bit of redundancy I suppose as they are buried in the wall now. The original was solid copper, the new one I ran is RG6. I also have a break in the line in my loft which is currently joined by a coax connector. I also have right angle coax elbows on my aerial socket. Last night I strung an old aerial up in my loft and connected it directly to the old copper coax. I also did away with the right angle connector. With this setup, the signal strength was slightly improved. I monitored the signal strength on BBC during the evening and could see this drop over a period from 70% to 50% while ITV and HD channels remained at around 75%. However, I did not get any picture break up as I do not believe the signal strength was dropping as much as before.

    This suggests that I can get away with a loft aerial quite easily. This would shorten the cable run and remove the in line connector. I am now going to try a different aerial as suggested but set up properly in the loft and see how this goes.
     
  11. ericmark

    ericmark

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    Fact that not all signals and it is at a set time of day plus Winter hill is high up, I would be looking at Isotropic propagation as Bernard Green said, not had it that much from Winter hill, it was a regular problem when I lived in Suffolk, what happens is hot and cold air produces a reflective layer for radio signals, this layer can both reflect signals going up down again and signals going down up again.

    The CB guys called it skip, and from the ground they could talk over a lot longer distances to normal as the signal reached the layer and then followed it and came down again quite a distance further on, so for a transmitter aerial below the layer the signal goes further, however if the aerial on the mast is above the layer, instead of the signal coming down to you, it is reflected back up again.

    The radio amateurs near me found out during this isotropic propagation walking to the top of Moel Famau instead of getting further they got near nothing as they were above the layer. In Suffolk often one TV station with the aerial low on the mast still worked, but one with an aerial high on the mast failed as it was above the layer, also signals from Holland would cause interference at the same time.

    I have stopped using winter hill just got fed up with the continual re-tuning so moved to satellite so can't say if I am getting the same result, but winter hill is rather high so it would seem to make sense for this to be happening.
     
  12. Sam Gangee

    Sam Gangee

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