Lost Channels - Advice Required

Discussion in 'Freeview & YouView' started by SHardy, Jul 31, 2018.

  1. SHardy

    SHardy
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    A couple of days ago we lost quite a number of channels from Freeview and have not been able to get them back by re-scanning. A bit of background info...

    We are in the ME19 postcode area and use the Bluebell Hill transmitter in Maidstone.

    We have had the same aerial setup for over 10 years. Aerial is located in the loft and was (iirc) labelled as a "wide band" aerial when purchased. This feeds into a 4 way SLx masthead amplifier which runs down to the living room and to 3 bedrooms. One of the bedrooms houses the SLx PSU and the masthead amplifier has the jumper set accordingly. Signal strength and quality levels are usually both at 100% for all channels.

    We had Sky TV for a long time, only cancelling it about 9 months ago. But this was in the living room only. We have always relied on Freeview in the bedrooms.

    Back in April we had a lot of drop out, such as pixelation, for a few days before then losing most channels. After a few days I purely by accident managed to fix the issue by replacing the aerial lead that ran between the PSU and the wall plate. There is no reason to believe that external forces would have affected the existing cable that had been in place for many years. But the replacement was shorter and thicker, looking like it would be better quality.

    In early July we lost some channels late at night and couldn't get them back until the next morning upon re-scanning. I wonder if this was related to the scheduled re-scan required for 17th July. Indeed, we did see the same behaviour upon the scheduled date. All was ok between rescans and since the last one...

    Until a couple of days ago. We lost a load of channels, with the same being apparent on all TVs in the house. The channels that we lost were those on C32, C34, C39+ & C46. No amount of rescanning on any TV is bringing the channels back. However, having a further play last night I found that if I either powered off the PSU for the masthead amplifier or removed it completely then I got almost all of the channels back on the TV in the bedroom that houses the PSU. The signal strength and quality levels were much lower than before (between 40% and 60%), but I didn't notice any drop out at all. However, rescanning the downstairs TV whilst the PSU was powered off resulted in even fewer channels. Whilst I got some of the previously missing SD channels back (such as BBC1 & BBC2), I lost many others and lost all HD channels.

    Now what I am thinking is that as the bedroom with the PSU is jumpered at the amplifier for the power feed, then this must be the only aerial point with a direct feed from the aerial when the PSU is powered off. Hence why this yields much better results with the PSU switched off.

    So the question really is, what is likely to be causing these problems?

    My first thought is that perhaps either the PSU or the masthead amplifier has developed a fault and I need to replace them. Would this be the most likely cause and fix?

    Alternatively, is it at all likely that with the recent changes that the signal is actually too strong (if there is such a thing) and that the amplifier should be replaced with a splitter?

    I can't see that it would be purely down to atmospheric conditions, else I'd have expected to see this behaviour in the past. Of course the latest channel loss does appear to have coincided with the sudden period of heavy rain. However, with the aerial and amplifier inside the loft I don't believe that this could have had an effect either. And I'm not aware of having a leak in the roof. ;)

    Could anyone offer any suggestions or advice? Should I simply go the most obvious route of replacing the amp? If so, I don't seem to be able to find the same SLx kit, so any recommendations?

    Many thanks,
    Simon

    Update:

    So I believe that the masthead amplifier that I have is an SLx4M. I have found a scan of an old SLx product document from which I'd say that it is actually the SLx4M 27838R (I'll have to get up in the loft to check in order to be 100% certain). The document shows this as having a 12dB gain per split and confirms that there is no variable or switchable gain.

    I have found myself going back to the thought that perhaps the recent changes have resulted in a stronger signal which after the gain has been applied is too strong for the receivers. Is this realistic? If so, would I be best to try replacing the masthead amplifier with a different one that has variable gain, allowing me to reduce it from the current levels?
     
    Last edited: Aug 1, 2018
  2. Clem_Dye

    Clem_Dye
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    There have been lots of changes around the country recently to accommodate the com7/8 moves, and the type of issue that you report is not new. Have you checked the DigitalUK website to see what channels should be available at your location? It may be that your loft aerial isn't man enough, either in terms of gain or frequency coverage (regardless of it supposedly being a wideband type). Too much signal would still give you something, but with lots of break-up, the same as too little signal. What do you see in terms of SQ, PQ and channels if you connect a TV directly to the aerial, bypassing the amp/splitter altogether? If that's OK, then you have a potential culprit in the splitter. However, if you still get very little then you may need to consider getting an external aerial set-up. Has there been any recent building work locally that has blocked your line of sight to the TX? Has the aerial in the loft been disturbed at all? Does it point in the same direction as other external masts locally?

    This type of issue is a PITA to fix, but by starting at the aerial and working backwards hopefully you'll find the root cause without too much hassle.

    Clem
     
  3. SHardy

    SHardy
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    Hi Clem, thanks for taking the time to reply.

    Years ago when I lived elsewhere I believe that we received channels from two different transmitters. However, where I am now is pretty close to the Bluebell Hill transmitter in Maidstone that delivers all Freeview channels. Indeed, I am aware of what channels we had before and did check on ukfree.tv regarding coverage and which channels are delivered on which multiplexes.

    I have had the same setup in this same property for over 10 years. This has always resulted in 100% signal strength and quality on all channels. That said, our signal was very poor with out the masthead amplifier all those years ago (when the analogue channels were still live too). Since then I have never had reason to remove it. The loft is only used for storage so is rarely accessed. When we had the drop out in April I did go up there to check that it hadn't been disturbed by birds getting in or similar, but there was nothing of the sort. The aerial and masthead amplifier are located at the back away from the area that is used for storage, so should always be pretty safe from clumsiness. There is no reason for anyone to go anywhere near it. When originally fitting the aerial I didn't get all scientific and find the exact angle it should be mounted at, but did use the roof mounted aerials down our road to determine the rough direction. It has not been moved since. There are no new building developments on the area which would affect the line to the transmitter.

    I am currently unable to remove the masthead amplifier from the equation as I will then only be able to feed one TV. But the aerial point in our bedroom is the one that is jumpered for passing back the 12V power feed and so appears to have a connection directly to the aerial as a result. When I remove the power feed either by switching off or removing the PSU the TV connected to that aerial point then gets nearly all the channels again (I think I only noticed one that didn't appear to be working). Sound and picture appeared fine (during my very short test), but the TV reports lower than usual signal strength and quality.

    I have now ordered a new masthead amplifier (the Antiference MHK4LTE) that has features that my current one doesn't. Namely variable gain and built in 4G filter. The gain can be reduced to as little as +1dB. So that is 3 possible issues that this new amplifier should be able to solve... (1) Faulty masthead amplifier or PSU (2) Too strong a signal after amplification due to recent changes (3) 4G band interference. That latter which I never considered. It is an easy and cheap solution, but if it doesn't help then this of course must leave the problem as either the aerial itself or the cabling. But I can't believe that each of the cables to the 4 points would be bad.

    Whilst it was originally only a secondary thought, I am now leaning towards the issue being that certain bands have significantly increased in signal strength and that the amplification is just too much. This is because with the amplifier powered up all 4 TVs in the house are missing the exact same channels but with those channels that remain still showing as 100% signal strength and quality. I will be able to update accordingly next week once I am able to replace the amplifier.
     
  4. TJT1

    TJT1
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    Can you be more specific about which channels you have lost. Concisely, if possible.
     
  5. SHardy

    SHardy
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    If you look at this page...
    Bluebell Hill (Medway, England) Full Freeview transmitter

    There is a list by multiplex option (selected by default). I went through these and was able to confirm that every channel listed under C32 (com7), C34 (com8), C39+ (COM5/ArqA) and C46 (PSB1/BBCA) were missing and all channels from all the other multiplexes were ok.

    Weirdly enough I just took a look at the channel list again to double check, and all channels are back again now. All at 100% / 100%. Also just been upstairs to check the bedroom TVs, and sure enough they're all ok now too. Not sure exactly when they came back. They still weren't there last night, but I didn't check this morning.

    So now I am really stumped. This must mean that over the last few days either there was an issue with the transmitter that wasn't being reported or there was something local to me interfering with those frequencies. No idea what that could have been though, or if it will return. Also means that I have probably wasted my money ordering this new masthead amplifier.
     
  6. TJT1

    TJT1
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    Then send it back if you bought it on line.
     

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