RTÉ is being broadcast behind TV3 on ntl analogue - Dublin

PK - the king

I don't know if anyone else has this problem, but lately on all of my TV's connected to the analogue feed, I can see a "ghost" image of RTÉ One behind my TV3 reception. It's very annoying as I can just see an outline of what's happening on RTÉ when I'm trying to watch TV3. I have the analogue feed connected through an NTL digibox modulator, but when I connected my TV's to the direct cable feed in, the problem was even worse. It's (obviously) not my digital affecting it, and there is nothing wrong with my TV's or co-ax. Why is this happening?

Any help appreciated...

mike65

Sounds silly to say about cable but...high pressure?

Mike.

Belfunk

It happens to me aswell. I have my bedroom tv wired up from my main tv point down stairs and for some reason i can see an image of RTE on TV3

gorm

Yep, I've seen it too. My NTL analogue is less than perfect all the time. I've had 7 breaks in service (including a whole week-end) since december. what I discovered was that when the service went down, I got reception of RTE on the telly were TV3 was. The reason is, I think, is than NTL broadcast on cable at the same frequency that RTE use for terrestrial broadcasts in the VHF so the cable acts as an aerial. I've given up using NTL on a second telly and use an ordinary outdoor aerial for it. Reception of the 4 terrestrial stations is light-years better than that provided by NTL analogue.

Mike 1972

Why cant NTL use the same VHF channel for RTE 1 and 2 as is transmitted locally.

At least then when the cable breaks down people would be able to plug in a "rabbit ears" and still watch RTE

Some Chorus networks transmit RTE on the same channel as used locally on VHF others stay clear of the local RTE frequencies and use Band 1 for the RTE's instead

Another flaw in the Dublin cable network is the fact that it leaks like a sieve (probably because a lot of the trunking is done with RG58 rather than the thicker Commscope) Cable Radio signals come in loud and clear on car radios and houses not connected to cable. I wonder about those S-band and midband signals leaking and messing up two way radio ?

bazzer

NTL's Dublin analogue channels are transmitted in harmonically-related carrier mode, which means the channels rely on each other's harmonics to stay within limits and not drift off-frequency. They are evenly spaced at 8MHz apart - 176MHz, 184MHz and so on.

Relaying, say, RTE1 by cable on the same Kippure transmitter frequency of 183.25MHz would need a total system re-alignment to take account of these off-set frequencies. Many customers without automatic tuning TVs would have to re-tune all channels. Not by a lot admittedly, but I can't see NTL plumping for that because of the sheer hassle.

Transmitting a channel by cable on the same frequency as an off-air service would leave it open to ghosting and interference (even if it's the same service e.g. RTE1) due to poor screening cable still in use in many areas of the city, as mentioned above.

PK - the king

Well, I don't think it is a cable problem as I am living in a digitally (but not broadband) enabled area in Dublin, so all of the cable is CT-10 grade. I don't use any splitters except the one ntl installed for my digital, whereby the splitter is insulated and has a booster function.

It's a right pain in the arse :mad:

PK - the king

TG4 looks grand. I'm just getting "Spaklies" on UTV and a ghosting image of RTÉ behind TV3.

I couldn't be bothered getting ntl to look at it for me. They haven't fixed my problems the other seventeen times they've had someone out. I have someone supposed to be coming from sky on thursday Hope he comes this time though.

PK - the king

Oh, and it IS a silver T-shaped splitter I have

Antenna

Originally posted by bazzer
NTL's Dublin analogue channels are transmitted in harmonically-related carrier mode, which means the channels rely on each other's harmonics to stay within limits and not drift off-frequency. They are evenly spaced at 8MHz apart - 176MHz, 184MHz and so on.

Relaying, say, RTE1 by cable on the same Kippure transmitter frequency of 183.25MHz would need a total system re-alignment to take account of these off-set frequencies.

Yes
But why not use the nearest cable 'harmonically-related' carrier frequency to the off-air carrier???
If 183.25MHz is RTE1 broadcast in the air, therefore use 184MHz for RTE1 on the cable??

Of course this wont stop the ghosting, - But the ghosting will now be that of the SAME TV station.
Surely ghosting of a different station is a lot more noticeable/annoying than ghosting of the same station???

John R

Originally posted by Antenna
Yes
But why not use the nearest cable 'harmonically-related' carrier frequency to the off-air carrier???
If 183.25MHz is RTE1 broadcast in the air, therefore use 184MHz for RTE1 on the cable??

Of course this wont stop the ghosting, - But the ghosting will now be that of the SAME TV station.
Surely ghosting of a different station is a lot more noticeable/annoying than ghosting of the same station???

If it is on slightly different frequencies it won't be ghosting, just interference. It wouldn't matter if it is the same channel or not.

PK - the king

In the modern day of cable television technology there is no shortage of frequencys so there is no excuse for ghosting or having to re-broadcast channels on the same frequency.