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Traffic causes signal breakup on mux2


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Old 08-11-2013, 12:23
mrsupercomputer
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I live in Hull and get my TV signal from the Belmont transmitter.

Generally my signal is very good, but since I installed a second TV and ran a coaxial cable to it from the freeview box (it connects to the first TV via scart), the channels on mux 2 (itv, c4, c5, etc) break-up whenever traffic is heavy (or a noisy moped goes past). However, it only does so when the second TV is switched-on. If both TV's are turned on and tuned to a mux 2 channel, the picture on both will be bad, but as soon as the second TV is turned off, the picture on the first TV improves dramatically.

It's a bit strange, and quite annoying as I live on a main road. Can anyone please explain what's happening? And maybe suggest a fix?

Thanks for reading, xx
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Old 08-11-2013, 12:35
Marti S
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You don't say how you are splitting the aerial feed between the 2 TVs?

It would probably be best to use an amplified splitter.

Check to make sure that your coax braid is making good contact at all the relevant plugs, you could get interference on the cable if it isn't.
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Old 08-11-2013, 14:09
mrsupercomputer
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The freeview box connects to TV 1 via scart and TV 2 via the aerial-out/coax-feedthrough and the coax cable is off-the-shelf, sealed at both ends, perfectly intact.

There's a signal booster going from the aerial to the freeview box, and I get a good signal, but there isn't one going from the freeview box to the second TV. Is that necessary?

Couldn't I get a extra-shielded coax cable or some kind of filter to stop the interference feeding back into the freeview box?
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Old 08-11-2013, 14:44
chrisjr
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Sounds like the extension cable you are using to the second TV is poor quality. Not that unusual for ready made leads with moulded on plugs, even more so if the cable is fairly thin.

You need a good quality double screened cable to minimise losses and interference. Also the best place to have a booster and splitter is as close to the aerial as you can get. Then run the minimum amount of cable from there to each room.

The way you are doing it is possibly the worst option. You have a long run of cable from the aerial then another long run to the second TV. That won't do the second TV any favours. And if the booster is also downstairs behind the main TV then it is also amplifying all the crap that gets into the cable between it and the aerial. That is why the best place for any amplifier is near the aerial to get the cleanest signal possible and also to overcome the losses in the cable run.

You might get a better result using a two output booster and plugging the second TV into that instead of the Freeview box. And using a better quality of cable as well. Assuming the option of splitting/amplifying closer to the aerial is not possible.
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Old 08-11-2013, 23:42
Winston_1
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The way you are doing it is possibly the worst option. You have a long run of cable from the aerial then another long run to the second TV.
I don't agree. The first Freeview box will have a small booster to overcome the splitting loss to its output socket. Almost certainly the problem is poor quality cable from there to the second box. Make up your own cable with satellite grade double screened cable. Just make sure you wire the coax plugs correctly.

http://www.megalithia.com/elect/bellinglee/index.html
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Old 09-11-2013, 08:21
David (2)
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I don't agree. By using the rf pass thru on a box to get a signal to another box/tv puts in a risk of rf noise contamination from the first box. These r often low quality devices with poor rf isolation not only from external sources but internal to the box as well (Eg power supply).

In this fast paced digital tv world the rf feed is a dying legacy anyway so u may not always have this daisy chain option when u buy a new box + both tvs show same ch (very last century).

I would recommend 1 aerial with a multi way splitter or multiway booster (depending on how strong your signal is, using a booster where its not needed just adds the risk of boosting and making worse the interference), with a cable going to each room. Each tv then operates on its own with either its built in freeview or box.

The only type of splitter I would use is a all metalised one, not one of the cheap plastic things.
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Old 09-11-2013, 08:24
David (2)
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If the interference Still happens it may then b time to look at getting the aerial re sited Further away from the road, other side of house etc. If that doesn't work or can't b done then the final options might b going to freesat or sky or cable.
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Old 09-11-2013, 10:33
chrisjr
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I don't agree. The first Freeview box will have a small booster to overcome the splitting loss to its output socket. Almost certainly the problem is poor quality cable from there to the second box. Make up your own cable with satellite grade double screened cable. Just make sure you wire the coax plugs correctly.

http://www.megalithia.com/elect/bellinglee/index.html
I very much doubt any booster in the Freeview box is doing any more than a couple of dB gain. I certainly don't notice any significant change in signal level on my kit if I feed the TV via the Humax PVR or direct. I would doubt it is enough to compensate for the losses in a cheap and nasty cable.

In any case "worst" is a relative term. If you have the choice of splitting/amplifying at the masthead, running the bare minimum of cable, or daisy chaining two long runs of cable the best option has to be the masthead and the worst has to be daisy chaining does it not? Relative to each other.
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Old 09-11-2013, 10:37
chrisjr
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I don't agree. By using the rf pass thru on a box to get a signal to another box/tv puts in a risk of rf noise contamination from the first box. These r often low quality devices with poor rf isolation not only from external sources but internal to the box as well (Eg power supply).

In this fast paced digital tv world the rf feed is a dying legacy anyway so u may not always have this daisy chain option when u buy a new box + both tvs show same ch (very last century).

I would recommend 1 aerial with a multi way splitter or multiway booster (depending on how strong your signal is, using a booster where its not needed just adds the risk of boosting and making worse the interference), with a cable going to each room. Each tv then operates on its own with either its built in freeview or box.

The only type of splitter I would use is a all metalised one, not one of the cheap plastic things.
BIB. Not entirely sure what you mean by this. If you daisy chain the aerial to a TV via a Freeview box then the Freeview box and TV are free to watch any channel available independently of each other.

Unless you are thinking about something like a Sky box with built in modulator?
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Old 09-11-2013, 20:55
Winston_1
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I very much doubt any booster in the Freeview box is doing any more than a couple of dB gain. I certainly don't notice any significant change in signal level on my kit if I feed the TV via the Humax PVR or direct. I would doubt it is enough to compensate for the losses in a cheap and nasty cable.

In any case "worst" is a relative term. If you have the choice of splitting/amplifying at the masthead, running the bare minimum of cable, or daisy chaining two long runs of cable the best option has to be the masthead and the worst has to be daisy chaining does it not? Relative to each other.
The booster in the Freeview box is only a few dB gain, just enough to overcome the splitting loss. So the output will be the same level as the input. Taking a feed from here half way between the aerial and box 2 should be no worse than a twice as long feed from the aerial.
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Old 09-11-2013, 21:28
chrisjr
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The booster in the Freeview box is only a few dB gain, just enough to overcome the splitting loss. So the output will be the same level as the input. Taking a feed from here half way between the aerial and box 2 should be no worse than a twice as long feed from the aerial.
That assumes the direct route is the same as the current route. Which may not always be the case. What if the second TV is actually in a bedroom directly below the aerial?
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Old 13-11-2013, 14:25
mrsupercomputer
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Well thanks for the replies everybody but I don't suppose they're important now because the second TV has conked-out. Keeps turning itself off and on. But before I replace it, do you suppose that the coax interference could have damaged the unit?

It's annoying because the interference hasn't actually been that bad the past few days
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Old 13-11-2013, 14:37
Nigel Goodwin
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Well thanks for the replies everybody but I don't suppose they're important now because the second TV has conked-out. Keeps turning itself off and on. But before I replace it, do you suppose that the coax interference could have damaged the unit?
No it couldn't.
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