Picture Break Up - Sutton Coldfield Transmitter

[Leonthefixer]

Take the booster out. If you are going to put it anywhere, then it needs to go at the top of the cable, probably after the splitter in this case.
There is very little to be gained (if anything) by putting it at the bottom.

prpr - could you expand on your reasoning about the splitter please so I can try to understand better why the position of it makes a difference.

The splitter seemingly improves the signal strength at present by having it at the end of the cable run just prior to the cable going into the Humax box going off the figures I posted above about signal strength, but you say it would gain very little if anything so I am confused.? (Easily done)

Is it that although it appears to improve the signal it is actually just amplifying any signal errors?

I would temporarily for now place it in the loft by running an extension lead into the loft from the hallway below to get power to it and the place it before or after the splitter. I am assuming it would be best to place it before the splitter? As I said above, when I tried to use the setup without a booster I was getting intermittent signal break up hence why I introduced it and it all seemed to run fine until the last couple of weeks where something seems to have changed.

Many thanks!

 

[Ezra Pound]

As you said in #1, your problems only started in the last few weeks, so something has changed recently, the transmitter does not have any reported problems at present so the change has happens at your end unless you was receiving a reflected signal from a building that has recently been pulled down . This points to a bad connection, moisture in / around the cable etc. Start with the easy fixes in the loft and reduce the number of connections to a minimum e.g. remove the splitter, signal booster and any loose connections and see what you get

 

[Leonthefixer]

Yes that makes sense. I did notice that last week I think it was there was some issue with the transmitter but I guess that can now be ruled out if there is no issues with it now and I am still getting issues.

There have been no change in buildings around em so that rules that out as well with regards to a reflected signal.

It seems like it is unlikely to be an issue with the box and rather the aerial or some part of it or the cabling as no one has mentioned the box in their replies.

I guess it is going to be a matter of trial and error - first step probably is going to be removing the splitter and putting a straight connector in.

 

[grahamlthompson]

How far away is the Sutton Coldfield mast from the OP's address ? The symptoms sound like classic overloading from a far too strong signal. If so a simple variable UHF TV attenuator should sort it out. DVB-T2 seems more prone to the issue (I had to fit an attenuator for a similar issue on the HD mux ).

http://www.screwfix.com/p/vhf-uhf-v...rch-_-SearchRec-_-Area1&_requestid=146309#_=p

 

[Leonthefixer]

Many thanks Graham - I am quite a distance, about 29 miles. I have attached an image that should give all the info. Our area is known for getting a weak signal so I wouldn't have thought that I would be getting too strong a signal, but maybe I am wrong. Any views after seeing the detail in the image would be great.

 

[grahamlthompson]

Many thanks Graham - I am quite a distance, about 29 miles. I have attached an image that should give all the info. Our area is known for getting a weak signal so I wouldn't have thought that I would be getting too strong a signal, but maybe I am wrong. Any views after seeing the detail in the image would be great.

View attachment 1595

Unlikely to be overloading then. If I have it correct that puts you somewhere near Derby or Melbourne. What transmitter does the DTG detailed reception predictor say is best for your postcode ?

If you are stuck with SC, replace the splitter with a remotely powered variable output two way mast head amplifier.

http://www.amazon.co.uk/Vision-V20-22056-Variable-Amplifier-Antiference/dp/B00FSDNZNS

For more info on splitters and amplifiers see here

http://www.aerialsandtv.com/ampsandsplitters.html

 

[Leonthefixer]

Thanks for your help Graham, I am quite close to Kegworth which isn't far from Derby. All of the local aerials point towards Sutton Coldfield apart from those on higher ground that point to Waltham. Unfortunately due to the location of my house I have no option but to go for Sutton Coldfield as I am close to a railway line embankment which blocks Waltham and it is made worse by the fact that I am in a low house.

I purchased all of the equipment from Aerials and Tv that you link to and he was helpful on the phone. I think I will give them a call again and ask for their advice.

I would like to keep the splitter so that I can feed other rooms when I get around to wiring it up but in the mean time I have got some ladders and gone in the loft and removed the splitter and placed an inline connector in its place so they are connected like this, minus the tape:

This has led to the following readings on the signal strength compared to those before (The booster is still at the bottom of the cable run just before going into the Humax box - where it is indicated that a booster was used by a 'Y').

As can be seen there has been a marginal improvement in the Signal strength when the splitter has been removed and replaced by the inline connection.

I will try the booster before the break in the cable later today and update the readings.



Many thanks everyone!

 

[grahamlthompson]

Thanks for your help Graham, I am quite close to Kegworth which isn't far from Derby. All of the local aerials point towards Sutton Coldfield apart from those on higher ground that point to Waltham. Unfortunately due to the location of my house I have no option but to go for Sutton Coldfield as I am close to a railway line embankment which blocks Waltham and it is made worse by the fact that I am in a low house.

I purchased all of the equipment from Aerials and Tv that you link to and he was helpful on the phone. I think I will give them a call again and ask for their advice.

I would like to keep the splitter so that I can feed other rooms when I get around to wiring it up but in the mean time I have got some ladders and gone in the loft and removed the splitter and placed an inline connector in its place so they are connected like this, minus the tape:

This has led to the following readings on the signal strength compared to those before (The booster is still at the bottom of the cable run just before going into the Humax box - where it is indicated that a booster was used by a 'Y').

As can be seen there has been a marginal improvement in the Signal strength when the splitter has been removed and replaced by the inline connection.

I will try the booster before the break in the cable later today and update the readings.

View attachment 1596

Many thanks everyone!

The owner Justin regulary posts on AV Forums. In general it's much better to use one amplifier as close as possible to the aerial and then split after it. That way you don't amplify unwanted signals picked up on the coax downleads. That's why I suggested the masthead amplifier as these have low noise figures compared to the el cheapo plug in boosters.

 

[Trev]

Signal strengths etc. look fine and just as you might expect with/without amp/splitter.

With the PQ at 100% for most of the time and 0% occasionally, I would be looking for something that causes total loss of signal at the receiver unless, when you get 0% PQ you still get the good signal strength readings. If when you get 0%PQ with a good signal lever, then it's more than likely interference form somewhere.

As your problem has recently arisen, its more likely to be a dodgy connection or water in the cable somewhere, and as it's intermittent, sometimes OK and sometimes bad, then a dodgy connection seems more likely to me. Have you been able to check the signal strength when the picture is dodgy?

I will try the booster before the break in the cable later today and update the readings.

You will probably notice no difference and is basically a waste of time in your fault finding quest. You need to find out what appears to be a severe loss of signal (or the source of the interference) when the signal is giving 0%PQ.
My guess would be a dodgy connection in the aerial, that makes and breaks as it is blowing around in the wind. (or heavy interference)

 

[grahamlthompson]

There can be other reasons. A few years ago I lived in a house where the direct line of site to Sutton Coldfield passed over the Longbridge car plant. During an expansion of the plant some large cranes were erected. With at least one of the cranes when swinging the boom caused similar effects (this was way back before DTV).

It got quite a lot of coverage in the press at the time.

 

[Ezra Pound]

Leonthefixer : When taking the measurements for the 4 tables in #27, did you notice if any of the 4 setups were any more (or less) stable than others?, or did they show the same amount of picture break-up?

 

[Black Hole]

Is it that although it appears to improve the signal it is actually just amplifying any signal errors?

Yes. An amplifier is best placed at the lowest-noise point in the signal path, because any noise at that point will be amplified as much as the signal and you are stuck with that signal-to-noise ratio. The idea is to build up the signal power before you send it down the distribution path rather than after.

The only reason this might not be appropriate is if the signal is so strong as to overload the amp or the receiver input, in which case you probably don't need an amp anyway. If you need a distribution amp to provide multiple feeds downstream, the input may need to be attenuated to suit.

Digital TV can tolerate a much lower signal-to-noise than analogue and still extract a perfect signal, but analogue degrades gracefully (the picture noise builds up but you can still see it) whereas digital just drops off a cliff.

 

[MikeSh]

A long shot - you mentioned a railway line. From what you said I imagine it is behind your aerial, but possibly a passing train could reflect enough signal to mess up a marginal strength signal. Or could be interference if it's an electrified line. (No, I don't know why it should have been OK and not now )
Solution would be a high-gain, highly directional aerial if you don't have one already.

 

[prpr]

Do you not mean before the splitter prpr?

Ordinarily I would say yes, but I was being cautious in this case as excess signal going to the other outlet on a shorter downlead may not have been desirable.
It's difficult to say for certain because we don't know the characteristics of the amp (gain/noise figure), nor do we know the length/loss on the downleads, nor the amount of signal coming off the aerial in the first place (nor any levels of interference that are probably causing the problem).

 

[prpr]

prpr - could you expand on your reasoning about the splitter please so I can try to understand better why the position of it makes a difference.

The splitter seemingly improves the signal strength at present by having it at the end of the cable run just prior to the cable going into the Humax box going off the figures I posted above about signal strength, but you say it would gain very little if anything so I am confused.? (Easily done)

Is it that although it appears to improve the signal it is actually just amplifying any signal errors?

BH has already said it. In simplistic terms, the signal at the bottom of the cable is lower than at the top, due to the loss of the cable. Unfortunately noise theory tells us that noise doesn't reduce in the same way, so you are effectively amplifying a more grotty signal.
In digital systems, it is not the overall level of the signal that is usually important - it is the signal/noise ratio (more usually carrier/noise for digital) and it is worse with the amp. at the bottom than the top. An amp. doesn't improve the ratio - it makes it worse - it amplifies the noise as well as the signal.

I would temporarily for now place it in the loft by running an extension lead into the loft from the hallway below to get power to it and the place it before or after the splitter.

You really want an amp. that is powered up the aerial cable so you can locate the PSU and the amp. in different places, for exactly this reason.

 

[prpr]

I am quite close to Kegworth

I wonder if the intermittent loss may be aircraft related given your proximity to EMA? Bit of a long shot but you never know. Not a lot you can do about it though.
I used to live a mile or so from the end of the runway at Manchester and planes going over caused dreadful fluttering on the picture (analogue then), as well as driving me bats with the noise.

 

[Black Hole]

Digital is supposed to be relatively immune to multipath interference, but that can only go so far. In a high signal strength area it is possible to reduce a multipath problem by strategic off-aiming of the antenna.

 

[Leonthefixer]

Firstly, many thanks to all of you for taking the time to reply - it is very much appreciated. To run through the various points that have been raised:

In general it's much better to use one amplifier as close as possible to the aerial and then split after it. That way you don't amplify unwanted signals picked up on the coax downleads. That's why I suggested the masthead amplifier as these have low noise figures compared to the el cheapo plug in boosters.

The booster I was using is a cheap one that has been kicking around for probably the last 10+ years. So it was by the sounds of it doing more harm to the signal than good especially by having it situated at the end of the cable run - basically boosting the problems.

Signal strengths etc. look fine and just as you might expect with/without amp/splitter.


With the PQ at 100% for most of the time and 0% occasionally, I would be looking for something that causes total loss of signal at the receiver unless, when you get 0% PQ you still get the good signal strength readings. If when you get 0%PQ with a good signal lever, then it's more than likely interference from somewhere.

On the few occasions I have witnessed the issues live it has been the case that the picture quality drops right off but the signal strength remains as was. Which from what you have said indicates that the issue would more than likely be interference from somewhere.

You need to find out what appears to be a severe loss of signal (or the source of the interference) when the signal is giving 0%PQ. My guess would be a dodgy connection in the aerial, that makes and breaks as it is blowing around in the wind. (or heavy interference)

When I removed the splitter the connections seemed to be fine and the cable still looked to be in the same condition as when it was installed. The connection on the cable into the booster was not great though I noticed so I will look to re do that connection if I reintroduce the booster.

Leonthefixer : When taking the measurements for the 4 tables in #27, did you notice if any of the 4 setups were any more (or less) stable than others?, or did they show the same amount of picture break-up?

When I took those measurements the setup that was causing issues was when the splitter and the booster were in use. But as I say that same setup has been okay for several months. As for the other setups, I have not used them really yet so couldn't comment on picture break up levels/stability yet.

A long shot - you mentioned a railway line. From what you said I imagine it is behind your aerial, but possibly a passing train could reflect enough signal to mess up a marginal strength signal. Or could be interference if it's an electrified line. (No, I don't know why it should have been OK and not now

) Solution would be a high-gain, highly directional aerial if you don't have one already.

The railway line is behind me but I don't think it would be trains causing the issues as it is not a busy rail line and I am well shielded by the embankment and I am down the hill from it.


The aerial I have is the Yagi18B as sold by Aerials & Tv : http://www.aerialsandtv.co.uk/atvschoiceofaerials.html#Yagi18


This was purchased on the advice of the person who runs the site/shop.

I wonder if the intermittent loss may be aircraft related given your proximity to EMA? Bit of a long shot but you never know.

I don't think this is a likely cause as although we are close to EMA we are away from the flight path.

Digital is supposed to be relatively immune to multipath interference, but that can only go so far. In a high signal strength area it is possible to reduce a multipath problem by strategic off-aiming of the antenna.

As I understand it, I am in a low/poor signal strength area.

 

[Leonthefixer]

So - last night I settled down to watch the TV recordings from the evening fully expecting the same issues that I have been having recently. The setup was such that the splitter is removed from the setup and the booster is removed. So the cable comes down from the aerial into the loft space as has been the case since installation.

In the loft the splitter has been removed and the cable joined by using an inline connector. The cable then runs down into the lounge and now straight into the Humax box, the booster is not in use.

Low and behold, a whole night of recordings and not a single picture break up!

So to me that would indicate one or more of the following were potentially the problem:

1. The splitter - (when removed the cables and connectors seemed in fine order and they are now still making a connection through the inline connector. So it would seem to indicate they were making a good connection before. So the issue perhaps was with the splitter and not the cabling).

2. The booster - when removing this the connectors were not the greatest, I must not have made the terminations the best. So it could have been that the connectors were the issue but also/instead the booster itself was causing the issue by boosting the interference and making the noise/signal ratio worse not better, if I have understood how they work. The fact the picture was fine all night indicates there may be no need anyway for the booster, though when I first installed the setup with a splitter in the loft I did get some picture break up, that was not present last night though from memory it wasn't the case all the time back when I first did the setup a few months ago. However, the issues only started in the last few weeks so why would the booster all of a sudden start to cause issues?

From what has been said above it seems that it may have been an iffy connection on the cables going into/out of the booster. As I say they didn't seem the best but why would they be fine one minute and not the next. They were just sitting there the whole time in the lounge not being moved around by anything.

3. The weather - last night it was not windy so the aerial wouldn't have been getting moved around so perhaps if this was the cause it would have been fine regardless of removing the splitter and booster

4. Some other unknown factor

So I think what would be the best course of action for now is to leave the set up as it is with both the splitter and the booster removed and see how the picture is over the next few days. If there is no break up I think it would be safe to say that the issue was either with the booster or the splitter - I am leaning towards the booster.

Then what I could do is reintroduce the splitter but leave the booster out and then see how things go with that set up - but as I say, when I had this set up originally it did cause some picture issues. Then I could remove the splitter and reintroduce the booster and see if the picture break up happens. I know the booster by the sounds of it is not needed and should not be placed at the end of the cable run but it would be nice to see if the issues returned when I reintroduce the booster as that way I would at least be confident in knowing that that was the cause and could stop the hunt.

If the above are fine the last step would be to go back to trying both the splitter and the booster and see if the issues come back, again just for peace of mind as to where the problems are coming from and so I can be happy with the aerial and cabling.

Many thanks again for all your time and any comments/advice would be most welcomed still.

 

[Ezra Pound]

Introducing the splitter is reducing your signal by half, this is not a problem if you are next door to the transmitter, but at nearly 30 miles away you can't afford the loss, all connections (however good) will introduce some reduction to the signal and are best kept to a minimum