TV coax cable and splitters/amplifiers issues etc

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I have been having issues with my tv signal after some building work. I have checked the cables as best I can and can't find anything wrong so I've decided to replace it whilst I can run the cables under the floor boards.
Currently I have a old inaccessible 4 way masthead amplifier with the cables routed in the void between roof tiles and plasterboard to various parts of the house. I suspect either the power supply (plugged in downstairs) or the amplifier may be the issue but cannot get to them to check.
After reading up I plan to replace it all, running a single cable to a distribution board where I can run new coax cables to each room in the house quite easily using the following:

https://www.screwfix.com/p/labgear-lma113r-1-way-masthead-amplifier/2100x
https://www.screwfix.com/p/labgear-ldu608g-s-8-way-home-distribution-unit/44218
WF100 cable

I'd appreciate any advice, We would likely only use 2 TV's at any one time and do not have sky/virgin at the moment..

Thanks
Tony
 
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The labgear 8-output amp is a bit OTT for what you need. The satellite inputs are a bit of a waste of time.

I'm a little busy right now but will reply in more detail later. In the meantime, do you know for certain that the aerial signal is so weak it needs amplification before splitting?
 
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Hi Lucid, thanks for your reply. I was thinking of future proofing a little. no doubt we'll have sky put in at some point.
To be honest i included the amplifier because there is one there already so assumed it must be required. the signal is certainly weaker without it judging by the tv picture when i unplugged the power supply.
 
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Lucid will know for certain but as sky are using a different type of lnb now will that amp handle the new type signal
 
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Hi Lucid, thanks for your reply. I was thinking of future proofing a little. no doubt we'll have sky put in at some point.
To be honest i included the amplifier because there is one there already so assumed it must be required. the signal is certainly weaker without it judging by the tv picture when i unplugged the power supply.

Without the remote PSU switched on, then any powered amplifier/splitter doesn't just stop amplifying or splitting. It also stops passing any signal at all.

No power means that the signal passing electronics stop working. Any signal the TV does pick up will be from poorly shielded coax acting as an aerial in a strong signal area. This would explain why the singalong looks bad or gone with the PSU turned off.
 
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hi yes sorry. i meant to say when i unplugged it before. interestingly i can disconnect the psu and plug straight into the wall socket and still get a weak signal but it just keeps pixellating.
it looks ancient but is a labgear psu. the amplifier was unbranded as far as i can remember
 
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With a masthead amplifier 13dB gain and a distribution amplifier another 7dB gain you will probably get into overloading. RF distribution is not just a matter of buying stuff and installing it. You need to measure signal levels, bit error rates etc and design the system.
 
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hi lucid just re read your reply. so if the signal i am getting is from the coax, i can safely say either the psu or the mast head amplifier is faulty as when plugged in the signal is no better? either way as i said its old equipment and now inaccessible. its a converted bungalow so i can easily get to the aerial and run a new coax striaght to a distribution amp without the mast head amplifier. should i do that first and see what the signal is like?
 
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In a sense @winston1 is correct, and those of us who are professional installers do just that. We match the most suitable aerial to the local transmitter's frequency spread, and then measure the signal level from it with our professional meters which gives us all sorts of insights in to the signal performance. As a DIY installer though you won't generally have this sort of level of professional meter, but that doesn't mean you can't make your own assessment of signal level and potentially the signal quality too.

Your TV probably has some sort of display for strength (S) and quality (Q) in the tuning menus. Dig a little further and you might find a sub menu for signal condition. This will give a Bit Error rate.

Once you've found these tools, then the next stage is to hook up the signal from your aerial and do a little stress test. In this case, the stress comes from reducing the signal with some attenuators. This is the sort of thing LINK. These are available in fixed values from various sellers. You can do your own search. A mix of three at 3- 6- and 15dB would give you the ability to attenuate at 3, 6, 9, 15, 18, 21 and 24dB by combining them.

The next step for you is to make up a short link cable so that you're not putting the TV aerial socket under a lot of leverage strain by connecting a 6" long attenuator stack with the weight of the main aerial coax hanging off the other end.

Once you have the hardware side of things sorted, you'll do a little research in to what your local TV transmitter is called and the mux channels it broadcasts on. To do this, use the postcode checker here: Detailed transmitter information for industry professionals | Freeview Enter your postcode and house number. The information that comes back is a list of the most likely transmitters, and the RF channel numbers that each of the mux groups is found on, and then a signal level prediction.

For example, say I lived in Halstead at 7 Ravens Road CO9 1NZ; here's what the search would show:

transmitter prediction.jpg


The above tells me that my most likely transmitter would be Sudbury, and that I'd be picking up transmissions on RF channels 29, 31, 37, 41, 44 and 47. The site's best guess is that the signal from these would be pretty strong right the way across the board. However, your aerial and where it is positioned and how it is aligned might change things.

Armed with this info, the next thing I would do is a quick tour of each RF channel to look at Strength and Quality. If any is weaker than the rest, then this is the one to start with. What we're doing in this next part is to reduce the signal level in progressively larger steps to see if and at what dB level the Quality starts to change.

You can think of quality as the difference between the signal and the background noise. (There are other aspects to it, but this definition will do for now.) Reducing the signal strength shouldn't affect the Quality until we reach a tipping point. If it takes say 21dB of attenuation to start to change the Q reading, then we can make an educated guess that there's at least 19 or maybe 20dB of safety margin. At that sort of number, you definitely don't need an aerial amp. But if you were to do the test and found that things go south with say just 6dB of reduction, then I'd be tempted first to look at the aerial type and group to check if it's a good match for the transmitter. If the aerial was a Wideband High-Gain type, then it's reception favours transmissions from roughly RF ch40 through to the now obsolete ch68. It wouldn't be a good match for Sudbury. To test this, I would compare the stress test results for channels 29 versus 47. The result I would expect is for ch47 to stand up to more attenuation than ch29 which is well out of band.

There's more info on aerial groups on the excellent AerailsandTV website here: Wideband / grouped TV aerials - A.T.V. Poles, Brackets, Clamps & Aerials (aerialsandtv.com)


What the results mean

When I install aerials, my meter allows me to deal in absolutes. I'm looking for a minimum of 50dB signal level at the lowest signal level TV aerial socket. At that level, I know that whatever the small signal level variations that occur, it's very unlikely that the TV would experience any reception issues except for say exceptional circumstance such as sunspot activity or someone setting up a pirate radio transmitter next door.

The average modern TV will accept a signal as low as 35dB, and even the least sensitive won't need that much more than 40dB, and so the difference between 40 and 50 dB gives me at least a 10dB safety margin. If you can manage to get at least 15dB of attenuation without affecting the Q reading then all you need is an amplified splitter. You won't need a masthead amp.
 
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