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Signal Strength

Z

Zico Barton

Member
I've just moved house and can finally get HD channels! but I've noticed some of the channels, especially in the evening, the picture corrupts and goes blocky.

The aerial is in the loft and I've no idea when it was installed, maybe even when the house was built in the 70s!

Looking in the system settings (can't remember exactly which menu) most of the channels are 100% quality and about 50% strength. One channel keeps jumping all over the place from 100% quality down to 10-20% then back.

Do I need a new digital aerial? I saw them in B&Q for £20, is that about right?

Thanks
 
Zico Barton said:
Looking in the system settings (can't remember exactly which menu) most of the channels are 100% quality and about 50% strength. One channel keeps jumping all over the place from 100% quality down to 10-20% then back.
Click to expand...

50% strength ought to be enough to give 100% quality. Which MUX has fluctuating quality? What stage of DSO are you at? Do you have any channels above 800?
 
I wouldn't be looking at replacing an aerial in the loft, unless it has to be there. Get one outside if you possibly can.
 
Zico Barton said:
I've just moved house and can finally get HD channels! but I've noticed some of the channels, especially in the evening, the picture corrupts and goes blocky.

The aerial is in the loft and I've no idea when it was installed, maybe even when the house was built in the 70s!

Looking in the system settings (can't remember exactly which menu) most of the channels are 100% quality and about 50% strength. One channel keeps jumping all over the place from 100% quality down to 10-20% then back.

Do I need a new digital aerial? I saw them in B&Q for £20, is that about right?

Thanks
Click to expand...

A new aerial might help, mounting on the roof might help, replacing the wiring might help. A combination of those will probably sort you but could be 1 or all 3 required. Maybe see what your signal is like for your area, see if a neighbour has a good signal, if so then you know it's your equipment and not where you live.
 
Sorry I didn't reply sooner, I've been away with work - not that you needed to know that!
When I go in to system settings it's channel 55 that the quality is low.

I've just installed the web-if pages and gone in to channel information.
To be honest most of the channels signal strength look pretty low (about 1/3) but all have 100% quality apart from 55.
55, 62 and 63 have the lowest signal strength, 63 being the HD channels which do cut up a lot.
I tried another aerial cable (from the hummy to the wall) and it helped a little, also twisting the cable into the wall socket sometimes fixes it for a bit.
Maybe its the faceplate?

There are no channels in the 800s, analogue isn't turned off until Sept 2012.
 
I had weak signal on my HD freeview channels and fixed it with a mains powred aerial amplifier. HD channel MUX went from 30 to 80% and all other channels stayed at 100%. Might be worth trying to find one with a variable amplifier as over amplification will also lead to problems.
 
But wouldn't it be better to see if there were underlying problems first? Perhaps not. It might be cheaper to just buy an amp!
Do you need a broadband aerial at your site? If the aerial is old, it's possibly a 'grouped' aerial for low band and you are trying to get high band signals. Which transmitter are you on and how far from it are you?
 
I had thought about an amp, I'll try that if I can't get it sorted another way.
No idea if it's a broadband aerial, how would I know? can you tell from looking at it?
We've just moved in to the house a couple of weeks ago so it could be the one the builders put in in the 70s.

It looks like the aerial is pointing to the Tyne Tees Pontop Pike transmitter. I'm about 10 miles from it and can see it from my window so I'm surprised it's says a low signal for all of the channels.
 
PP is group C/D on both analog and digital, so it appears that you do not need a broadband aerial and it is probable that the one fitted will be the right C/D band aerial. The front elements should be horizontal. You can find a multiplex/channel list Here for PP. You probably need to check the connection of the co-ax at both the aerial and wall plate end to make sure these are clean and free from corrosion. The patch lead from the wall plate to the set does not usually affect sig strength much unless it's eithe long or faulty.
 
I've helped somebody get from no ITV4 to full channels by substituting a thin string patch lead with a proper one. If you're on the edge of the digital cliff, even the patch lead can make the difference.
 
Like Blackhole says, it's worth 'revisiting' all your aerial connections, especially as this is a much cheaper option than buying an amp or paying to have the aerial moved to outside.

I was helping a friend who had bought my old Humax box from me to achieve a better signal. Some muxes were only showing a fluctuating 50% strength, and more importantly, a fluctuating quality. I had every co-ax connection apart and remade them, resulting in a 15% strength gain and more importantly steady 100% quality. Years of careless 'hoovering' I guess. Making your own patch cables from 'proper' aerial co-ax also means that you can tailor them to the exact length for neatness, even putting a 90-degree plug on the telly end so it hangs nicely.
 
Black Hole said:
I've helped somebody get from no ITV4 to full channels by substituting a thin string patch lead with a proper one. If you're on the edge of the digital cliff, even the patch lead can make the difference.
Click to expand...
I know it sometimes can make all the difference, but in my defence, I did use the words 'usually' much', and 'long or faulty' in my reply. Having said that, it would be a no brainer first thing I would go for, as it's a easiest to check out, but the OP said that he had changed that. His intermittency of signal seems more likely to be a dodgy joint in the co-ax run to me. (as advised by me and Chris above.
Surely he should get a good signal level being 10miles line of sight from PP. I know the TX is 10KW on digital and 500KW on analog, but surely an 'in the loft' aerial should be OK? I know an outside one would be better, but that's more expense of perhaps a new aerial, co-ax and the possible services of a rigger, n=making an amplifier look like a much cheaper option, after the connection checks:).
 
Further to my last, I wonder if he has a small aerial in the loft suitable for a 500KW tx 10miles away, which might just be a bit small for the 10KW of the digital TXs. Would an element count be in order?
 
Apologies for not replying to this earlier, I work away from home a lot and also have a 1 year old to entertain when I'm not working, so don't get much time to myself.

The current aerial is pretty small, I think it has 16(?) elements all of which are like small single rods.
I've bought an aerial from b&q, with 32 elements for use in high, medium and weak areas.
Testing it in the living room I was getting 80%+ on all channels. As soon as it went in to the loft it dropped to about 40%.

I also tested it with the original coax and the one that came with the new aerial.

The side of the loft roof facing the transmitter is a breeze block wall, would that cause the signal to drop soo much?

At 40% all channels seem to get 100% quality so I'm OK with the way it is, at least for the moment.

Thanks for everyones help and advice
 
Zico Barton said:
The side of the loft roof facing the transmitter is a breeze block wall, would that cause the signal to drop soo much?
Click to expand...
If it's real breeze, certainly. But if it's a modern house they are probably Thermalite blocks, much less dense. All the same, if the living room walls are studwork but the end walls are Thermalite (and the roof tiles don't help), the loft aerial is not doing you any favours.
 
Zico Barton said:
The side of the loft roof facing the transmitter is a breeze block wall, would that cause the signal to drop soo much?
Click to expand...

Yes, thats pretty standard loss. I have an aerial in the roofspace also. If you want to boost the signal, put an aerial amp as close to the aerial itself tha you can manage. I have one mounted on the pole that holds the aerial. Anywhere else and you are also amplifying any noise picked up by the coax on it journey to the tv.
Its also a must if you are splitting the signal out to feed other rooms.
I have a loftbox feeding 4 boxes.

It might also be worth getting your hands on a cheap digital aerial meter from B&Q or screwfix to make sure that your aerial is pointing in exactly the right direction.
 
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