Terrestrial Signal problem.

bluezulu49

Hi guys. I have an interesting problem with my tv reception setup.

I have a terrestrial aerial in the attic which feeds into a four output one input lnb on my 80 cm satellite dish. I do not subscribe to Sky.

This LNB combines terrestrial and satellite signals into single cables and has served three tvs for the past year, each cable being attached to a wall socket which splits out the combined signals to terrestrial and satellite.

Since the beginning of this month when I turn on my kitchen tv I get a message saying that there is no signal.

Terrestrial signal is restored when I turn on the Sky HD box which is connected to the aerial socket in the wall but at a lower signal level (69-70%) than when the Skybox is disconnected from the aerial socket (95%).

I have similar problems with my dining room tv which also has a Sky HD box attached. (TVs are Samsungs.)

Switching HD Skyboxes makes no difference.

Switching aerial sockets similarly makes no difference.

Interestingly the standard skybox in my sitting room does not exhibit the same problem, possibly because the signal is carried to the tv via scart rather than by hdmi cable as it is in the other two.

The cabling to the affected tvs is one year old and was done with good quality cable which does not appear to be damaged.

At this stage I suspect the problem lies with the one year old lnb. What do you guys think?. Thanks for reading.

Bluezulu49.

Peter Rhea

bluezulu49 wrote: »

Since the beginning of this month when I turn on my kitchen tv I get a message saying that there is no signal.

Terrestrial signal is restored when I turn on the Sky HD box which is connected to the aerial socket in the wall but at a lower signal level (69-70%) than when the Skybox is disconnected from the aerial socket (95%).

So you have the terrestrial aerial feed looped through the Sky box via RF-in? Maybe it's going into 'deep sleep' mode & disabling the signal passthrough? (Power LED will be red.) Probably started because of a software update?

Or maybe 'eco' has to be set up manually by the user: not too well up on Sky boxes, tbh.

Anyway, there is no point connecting the terrestrial aerial to the Sky box with the way your system is set up. Just plug it directly into the tv.

bluezulu49

Peter Rhea wrote: »

So you have the terrestrial aerial feed looped through the Sky box via RF-in? Maybe it's going into 'deep sleep' mode & disabling the signal passthrough? (Power LED will be red.) Probably started because of a software update?

Or maybe 'eco' has to be set up manually by the user: not too well up on Sky boxes, tbh.

Anyway, there is no point connecting the terrestrial aerial to the Sky box with the way your system is set up. Just plug it directly into the tv.

Hi Peter,
To clarify my setup, for each tv there is an aerial wall socket with two outlets, fed by a single cable from the lnb.

One outlet is connected to the sky box delivering satellite signal and one directly to the tv giving terrestrial signal. So terrestrial aerial is not looped through skybox.

This combining and splitting system was adopted as it was not feasible to get a second cable into two rooms which had been recently insulated, rewired and redecorated.

Bluezulu49.

The Cush

Peter Rhea wrote: »

So you have the terrestrial aerial feed looped through the Sky box via RF-in?

I think he has one of these combi Quad/Terrestrial LNB's - http://www.inverto.tv/products/product.php?section=1&id=77

http://www.boards.ie/vbulletin/showthread.php?p=86391869

bluezulu49

The Cush wrote: »

I think he has one of these combi Quad/Terrestrial LNB's - http://www.inverto.tv/products/product.php?section=1&id=77

Spot on. I couldn't remember the name of the item.

Bluezulu49.

winston_1

Does this LNB need to be powered by one of the Sky boxes before the terrestrial signal is passed through?

bluezulu49

winston_1 wrote: »

Does this LNB need to be powered by one of the Sky boxes before the terrestrial signal is passed through?

Hi Winston_1.

Just powered off all three and the terrestrial signal comes through fine.

Bluezulu49.

The Cush

bluezulu49 wrote: »

At this stage I suspect the problem lies with the one year old lnb.

Would it be possible to check the 2 problem cables from the LNB with the known good LNB output?

Peter Rhea

bluezulu49 wrote: »

Just powered off all three and the terrestrial signal comes through fine.

Completely powered off/unplugged at the mains?

bluezulu49

The Cush wrote: »

Would it be possible to check the 2 problem cables from the LNB with the known good LNB output?

Will do this tomorrow (Monday) and report back.

Peter Rhea wrote: »

Completely powered off/unplugged at the mains?

Pulled out all three plugs and full terrestrial signal restored.


Bluezulu49

Peter Rhea

At one of the affected tvs, try BBC 1 HD & Sky News & see if the selected channel makes any difference to the terrestrial signal on this tv.

St Senan

you can swap the output on the LNB feeding the box that works to 1 that is causing you trouble, just a process of elimination

This might have no bearing at all but are your Sky hd boxes switched to work on a single feed input and is the satellite feed from the wall plate going into lnb 1

Peter Rhea

The signs here would lead me to believe that the terrestrial signal is too weak to cope with whatever lnb noise in the UHF tv band is present on the cables. My suggestion to switch between high & low band channels & observe the effect on terrestrial signal, is to try & find an explanation for this:

bluezulu49 wrote: »

Terrestrial signal is restored when I turn on the Sky HD box which is connected to the aerial socket in the wall but at a lower signal level (69-70%) than when the Skybox is disconnected from the aerial socket (95%).

bluezulu49

Peter Rhea wrote: »

At one of the affected tvs, try BBC 1 HD & Sky News & see if the selected channel makes any difference to the terrestrial signal on this tv.

Hi guys. Apologies for delay in replying, I was ill for the last week. I tried changing Sky channels and found that with the skybox on BBC1 , 2 etc the terrestrial signal was fine but on changing to Sky news or any pay channel ( Sky 1 etc) the skybox killed the terrestrial signal.

As I was unwell I did not carry out the lnb cable swapping recommended.

However, full terrestrial signal has now reappeared and I suspect that Peter's suggestion of poor terrestrial signal was the problem.
The transmitter I use is Three Rock which is 8 km. away and is in line of sight from my roof.

I wonder did they temporarily reduce power?. Internet searches have revealed nothing.

In short full terrestrial reception has been restored without any intervention from me.

Thanks very much to all of you for your responses.

Bluezulu49.

Peter Rhea

I was working on the notion that switching the Sky box out of standby might have switched it from the 11778 mHz 'default' transponder (high band) back to whatever tp it was tuned to before going into standby (good chance of being low band on a non-sub. box) & that this was changing the character of the interference from the lnb.

The lnb specs give a figure of 13 dB insertion loss for the terrestrial frequencies, which is considerable. If you have trouble again, you might want to consider moving your aerial outside or, fitting an amplifier between aerial & lnb.

Antenna

As last poster said the Specs for that LNB for its terrestrial combine say

"Insertion Loss (MATV) 13 dB "


13 dB is a significant loss. You only have 5 percent of the signal strength of what you would have with one TV receiver connected directly to the aerial. And that is just from the LNB, also add the losses of the diplexer sockets which split the Sat and Terr signals again (around -3dB, worse at higher UHF channels), and cable etc losses
so you end up with not far off (if not at) -20dB (ONE PERCENT!) at each TV of what signal is at aerial


That is ignoring noise created by the LNB, which makes things worse again and for you is sometimes putting signals over the 'digital cliff'.

You say you have 3 TVs, If you could have ran seperate terrestrial cables, to a 3 way splitter (much less loss), all would be fine.

An amplifier between the terrestrial aerial and this LNB with terrestrial combine would increase the signal enough to overcome the losses, the amplifier requires power which you might not have easily have in the attic

Peter Rhea

I would re-site the aerial to a decent outdoor location. Get the best possible signal quality to begin with & probably a big enough boost in signal level to negate the need for an amplifier.

Eastmount

Hi lads I'm new to this so I'm sorry if I'm in the wrong area,I'm wondering if yous could help me. I have sky eyes set up on each tv in my house but I want to be able to watch the free channels(itv,bbc1 etc.) through an old sky box in the other sitting room. Can I use the same cable(from rf2 out on the main sky box) to give a signal to the other sky box? Thanks in advance

winston_1

Eastmount wrote: »

Hi lads I'm new to this so I'm sorry if I'm in the wrong area,I'm wondering if yous could help me. I have sky eyes set up on each tv in my house but I want to be able to watch the free channels(itv,bbc1 etc.) through an old sky box in the other sitting room. Can I use the same cable(from rf2 out on the main sky box) to give a signal to the other sky box? Thanks in advance

No, you need another cable from the dish.

Eastmount

Ok thanks. I have ran 2 cables from a central hub to all TVs and I was hoping I could watch freeview(BBC,itv on old sky box) and saorview on the other TVs. I have 5 connected cables from the dish at the hub, 2 which are being used for my sky +. So would it be possible to leave an old sky box and saorview box at the hub and split them to the other TVs? Sorry of it sounds too complicated..

winston_1

Freeview and Saorview can only be received from an aerial. If you only have cables from a dish at the hub you can only connect satellite boxes including Sky boxes. You can split the output of a sky box to as many TV's as you like (may need amplification) all of which will receive the same channel in analogue.

The Cush

Eastmount wrote: »

I have 5 connected cables from the dish at the hub, 2 which are being used for my sky +. So would it be possible to leave an old sky box and saorview box at the hub and split them to the other TVs? Sorry of it sounds too complicated..

Do you have an aerial installed for Saorview?

http://www.saorview.ie/what-is-saorview/make-the-switch/

Eastmount

Thanks for the info, yes I have an aerial in the attic and a cable ran from there to the hub aswell. I have sky set up in the main sitting room which I have sent out to the other 3 TVs through rf2 out and sky eyes which is working no problem. I just would like to be able to go to my 2nd sitting room to watch football on itv rte orbbc so my gf can watch sky in the main sitting room. Can this be done the way I have it set up or would I have to swap the cables at the back of the tv each time? I have 2 at each tv 1 being used for sky. Thanks lads..

The Cush

What equipment are you using at the "hub", an amp or splitter of some sort?

You say you have 5 cables from the dish with 2 being used for Sky+ in the main room, I assume 3 of these cable from the dish are unused at the moment? If so join one of these sat cables to the one of the two downleads to the second sitting room and connect your spare Sky box to it. That will give you the FTA sat channels such as BBC/ITV etc. but not RTé.

For RF2 from the Sky box use the other cable to the 2nd sitting room.

For RTé in the 2nd sitting room that will depend on what the aerial and RF2 setup is at the hub. They can both be combined at the Sky box in the main sitting by connecting the aerial feed to the RF in on the Sky box where it will be combined with the Sky signal out thru RF2, then it will only be a matter of tuning it in on your Saorview TV or STB at the 2nd sitting room TV point.