TV aerial?

Here we go... Wide view of whole aerial pole

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(The house is low two-storey, to give you an indication of overall height above ground)

Aerial itself

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The thingy at the bottom of the pole

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Next door have a weeny little bent-tin cheapo crappy thing mounted at ground floor gutter level. The few other houses in this little enclave have aerials very similar to ours in both altitude and style.

Reply to
Adrian
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If next door can get a decent picture on their TV set with that "weeny little bent-tin cheapo crappy thing" low down on the gutter then you should talk to them about it and get a similar device yourself.

It isn't compulsory to install your TV aerial as high as possible although usually it does help if there is a hill in the way.

Unless you are a really massive fan of "Dave" Freesat is the obvious choice in a remote location where TDTV is so difficult to obtain.

I remain curious as to how it is possible for the system to recognise the channels and channel IDs in setup without being able to at least partially decode some of them into jumpy video and broken sound.

Reply to
Martin Brown

That's why I thought getting a tv dongle for the puter might be worth doing.

I've never had a case where the scan detected a station that something didn't appear on screen and in the channels list.

Except one of my sony ST boxes which did similar and is now sitting behind me for the usual 3 year period before I sigh, realise it wont fix itself and throw it in the bin/.

Reply to
The Natural Philosopher

Despite the fact that my previous good professional advice was lost to you because of the mellée of uninformed speculation and sheer bollocks that surrounded it, I will say this: The aerial is a Vision V11-441 44. Google it. It is the right way up so the box won't be full of water. It appears to have been properly installed, so will most likely be correctly aligned. The grey box on the mast is a Vision brand amplifier. It's odd that the aerial cable goes into the right side. I know some old Vision products were like that, so maybe it's one of them. That housing is used for other things, but I should think it's an amplifier. The cables are not well secured so one of them might have pulled back in the f plug and thus not be making contact. The whole installation is quite old, by the looks of it. The amp could easily have been trashed by nearby lightning. If not you will definitely need a PSU to feed 12V to the amp. As I suggested before the first box inside will most likely be a PSU. Note that this could be faulty even if a simple meter says otherwise. If you have a telly with the option of putting 5V on the aerial feeder you could enable that and connect direct to the aerial. 5V will power the amp.

Bill

Reply to
Bill Wright

They generally show BERs after the FEC/interleaving etc is unwound, so it gives you very little information on the actual signal quality until its right on the edge.

Reply to
John Rumm

Medium to high gain yagi, can't see the colour of the end plug on the boom, but it looks like its probably a grouped aerial and not a wideband.

That is likely your masthead preamp. It will be powered by first of the boxes you identified as "amps" previously.

Does it work?

Reply to
John Rumm

not so sure about that. there are 'how many errors before correction' and 'how many errors after correction' collected somewhere. errors before correction can be quite high and yet still give a usable stream.

Reply to
The Natural Philosopher

A perennial risk...

Umm, OK. So that's a decent aerial, the right one for the transmitter, and shouldn't be my problem, right?

Always a good start.

OK, great. Certainly the rough direction appears to be both consistent with neighbours and fits the map.

It's going to be ladder o'clock, isn't it?

Not sure that's a great risk - it's a long way from being the highest thing in the immediate vicinity. But, again, I'm quite happy to be wrong.

Basic relevant history - the house was bought in the mid '90s, and a lot of work done to it - including new roof and a big kitchen extension (other end of the house to the aerial and all of the coax) - before they died in the mid-late '00s. Since then, the work to the place was finished off by their son and the house only used occasionally, but remained (very) fully furnished. The only TV here was a weeny ancient portable, no STB. Hence the likelihood that there's never been any Freeview watched here.

OK, I think you might have missed a post or three, too. Yes, the first box inside did turn out to be a Vision V23-100 PSU.

Turning that off and/or on makes a fairly big difference to the reported signal strength. Removing it from the line makes little difference. The other box is definitely an internal amp (Vision V52-100), which gives similar results disconnected to on, but a big (downward) difference connected-but-off.

Reply to
Adrian

Any idea why it is like that? Did the marketing department get to specify what diagnostics to display and choose the number that looks most favourable to the set and is minimally informative. The decoder must know how hard it is having to work and have these other numbers!

It would be much more useful to be able to see the raw BER - you can basically see the results of uncorrected errors in the output bitstream as glitches in the MPEG decoder long before "Quality" gets to 0.

IME anything with Q8 is needed for decent quality picture. I expect these Q numbers vary with maker (in my case Panasonic). I use FreeSat most of the time these days...

Reply to
Martin Brown

Quest and Yesterday are also missing on Freesat but present on Freeview

Reply to
The Other Mike

[Snip]

To get the amplifier working you need to have the PSU switched on. Any results you get without it being on are meaningless.

Is the "weeny little bent-tin cheapo crappy thing" pointing the same way as yours? or does it have the roads vertical and is pointing to the Clyro mast. If so, perhaps you should do the same.

One possibility is that the amplifier is being overloaded . If it was originally installed in the analogue days, the extra muxes, plus Clyro might well cause the "hundred or so channels" that you see. Or lighting damage might be the problem. The aerial doesn't need to be the highest point in the area, a lighting strike in the vicinity is all that is needed.

I don't think it's a DIY job, you need someone with suitable test equipment.

Reply to
charles

There are generally 105 or so channels on a full freeview installation.

The Ridge Hill transmitter is now using LESS power than it was when it transmitted analogue. Down from 100KW to 20KW per mux. So its doubtful that its overloading. Clyro miht be overloading it, if its actually pointing that way, but even so, I'd expect to see clyro stations available when the mast head and other amp are off. .

The really salient issue is that the 105 channels are detected reliably, but not displayed.

That suggest to me a fault in the STB, which is why I suggested buying a cheap PC TV adapter to eliminate that as a problem.

The fact that the fault developed at the exact time the box was shunted around in a removal van may or may not be coincidental.

I think its perfectly possible to DIY it, but it has to be done methodically.

The first thing to do is try a different STB. Because its easy and its cheap. And requires no ladder climbing.

Then move further up towards the mast head itself, to see where if anywhere the signal degrades.

BUT I have to say, degraded signal in my experience of half a dozen installations, ALWAYS results in 'channels not found' Not in 'channels found, but not displayed correctly'.

That combinations sounds too much like corrupted software in the STB itself. And its happened to one of my boxes here. I had the channels list, but didnt get any stations. Swapping the STB resulted in normality restored,. so that STB is for the bin.

I dunno how much a cheap STB costs these days - most seem to have recorders built in and are expensive, hence recommending a sub £30 PC dongle instead.

Oh. some STBS still available in that price range it seems.

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Reply to
The Natural Philosopher

You may get that level of detail on some of the PC based decoders, but its rare to see anything that detailed on your average STB.

Reply to
John Rumm

Not having studied the low level frame format used over the air in DVBT, I don't know what level of error identification is actually visible in the coded stream. However, with many FEC systems the small errors in the source stream simply get fixed in the process of decoding such that you are not even aware what they were or where they were. Its only once the stream is decoded and you can attempt to makes sense of the data, and have access to framing information, and checksums etc that you can tell what sort of quality of data you actually have.

The difficulty here is there is there not being a standard way of presenting this information - each box maker does their own thing, so you never know if you are comparing like with like.

Reply to
John Rumm

Ridge Hill has all its muxes in group A (on channels 21, 22, 24, 25, 27,

28), so yes the aerial is correct for the area.

Sadly, its not just a direct strike that can fry it...

Reply to
John Rumm

Right, that all makes sense...

Now we know that the first box is just a PSU (as a few of us suggested!) my suggestion to try just the second is less relevant.

Well that seems plausible in raw number terms... IIUC the splitter amp has about 13dB of gain (I could not find detailed specs for it - but Bill will have accurate figures I am sure), so overcoming the loss from the split etc, you would expect it to add about 10dB to the total - obviously we have know way of knowing how your STB translates power levels into percentages.

As you have discovered though, there is more to the game than just signal strength, and here is where it gets difficult to diagnose what is going on without access to test equipment.

Assuming that the aerial itself is receiving a good quality but weak signal, you will need the masthead amp to get a decent level of signal into the downlead before you start worrying about distributing it about the house.

However there are a number of ways in which you can run into problems here. The masthead amp might not be working as well as it should - it might have the expected gain, but for whatever reason is distorting its output. It could be its shagged. It may be its working perfectly, but there is a strong unwanted signal on its input that is within its bandwidth. This can overdrive it, and as a result the output is driven to its limits where it starts to "clip". That can then spray unwanted harmonics all over other parts of the spectrum including the channels you are after. Lastly the coax itself is old, and may be damper inside than we would like. Its also probably just "low loss" coax, rather than the modern type with an additional foil screen under the copper braid. The dampness etc (and poor connections from where its been flapping about unrestrained) can degrade the signal anyway, and the lack of screening will let more noise into the system in the first place.

In an ideal world you would need to meter the output from the aerial itself, and then work your way back down the system to see where the problem is actually being introduced. Needless to say the solution to fix a problem caused by a strong unwanted local RF signal is going to be different to say dealing with the effects of a knackered coax.

Without test gear, the best you can probably do is divide it up, eliminate as many unknowns as possible (e.g. internal distribution wiring), and test in stages.

Say for example connect your TV/STB directly to coax from the aerial, and turn on the power feed in the STB to power the mast head amp. If that get you a good result there then you could then introduce the Vision PSU and move to after it and so on.

Reply to
John Rumm

Some (typically older) STB boxes have a habit of sticking the first channels they find into the allocated "slots" and then moving duplicates found later to the high numbers. Annoying where the later ones are the better quality ones you are after.

Which IIRC due to the way the DTV system works amounts to the same level in practice...

Overloads can come from signals other than the ones you are attempting to capture though. I used to find it was a delicate balancing operation here prior to DSO to get enough gain to lift the DTV channels to a usable level, without over driving the amp with the analogue signals that were at the time 30 - 40dB stronger.

Reply to
John Rumm

OK...

I think this is what's happened and what is happening. Originally in analogue days this was aimed at Ridge Hill prolly then the only usable TX around. Since then the Clyro relay has come into use and that as far as relay stations go is quite a decent sized one, most small ones are a few aerials on a telephone pole!.

Now in DSO days the signals from Ridge Hill are being affected by what's coming from Clyro and of course thats on a different frequency group (B) its also behind the aerial but I rather suspect that there are a lot of reflections from other buildings, hillside's trees etc. So the TV is "seeing" a lot of rather confused crap termed intermodulation products.

So what do you do?. I suspect the home alluded to across the way with the "weensey" aerial is on Clyro and thats covering the town quite well but now that has a reduced number of MUX's and some progs are going to be missing and also as it's in Wales it does carry the output of Wenvoe a main Welsh station.

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I very much suspect the first Amplifier is working OK you can check this by seeing what's coming out of it on power then off power and if theres a lot less power off then its ticking OK they very rarely half fail and if it has been spiked by lightning then its prolly won't be going at all apart from in the bin!.

Now that amp is being fed with stuff it can't handle mainly the output of the local relay hence its generating the multitude of signals the TV is responding to but none of them are of any use!.

I rather suspect that the original problem here is a decent "clean" aerial signal the set top box I'd think is OK. Is there anywhere else you could tale it to test it at another location?..

Now you could filter off the local signal from your aerial but that would have to be done -before- the aerial amplifier which isn't easy to do!. Else get another aerial in B group and aim that less amp/s at the local relay and enjoy the TV albeit fewer muxes than otherwise and that area isn't to only one suffering the problem its usually down to insufficient frequencies available for the area the relay is located in..

Or go Freesat and do away with a lot of problems. A second hand sky box will suffice and dish and they as long as they can "see" the satellites are fine they needn't be that high of the ground ours are out in the back garden surrounded by shrubs, else get a digital satellite receiver or a sat card for your TV and they do work well the wife uses one here for French satellite TV.

FWIW This ng has some very well informed people hereon for TV, Bill Wright must be one of the most experienced aerial riggers in the UK and has a very interesting website. He has even rigged receiver aerials for the broadcasters!.

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Also mention to Charles Hope a long time member of the BBC reception advice team now a shadow of its former self as well as Martin and Mac and also andy wade if he puts in an appearance as well as TNP etc...

As to the latter person don't be too concerned by the lack of ERP as regards any TX they are differing systems and now Digital is more of a mean power whereas analogue was peak powers . Here in Cambridge I find that Digital reception is less demanding on "metal in the sky" than analogue!...

Reply to
tony sayer

I was thinking that having the PSU off would show the signal without the amp boosting it, but bypassing the PSU would show if the PSU was somehow interfering with the signal.

It is.

I haven't managed to speak to 'em yet to find out if they're using that aerial or not. I'm going to pop round to next-door-but-one and see if I can try my STB on their aerial to rule that out.

I'm starting to come to that conclusion, but it's as well to rule everything DIYable out first.

Reply to
Adrian

No, pointing same direction as ours - Clyro's t'other direction almost entirely.

Reply to
Adrian

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