Does a digital signal have a visable effect on a TV

trazix

I am in Donegal and get my Uk tv from Limavady. If it was

possible for me to receive DTT from Limavady I would like

to know what effect would it have on screen by tuning in

the DTT channels/frequencies on an analogue tv e.g. would i

see any thing other than a snowy background, I tried this

already and just got snow, could someone that gets DTT tune

in the channels (67,58,53,57,60,63) on there TV and tell me

what they see. Basicaly what I want to know is does the

digital signal have an effect on a analogue TV thats tuned

to that frequency.

You will see nothing by tuning in those channels on an analog uhf tv tuner.
The digital signal will only be received on a set top box which allows you to watch them on an external channel via a scart lead.

You will only get the service, if your limavady analog( ie the channels you are watching without the stb) is crystal (almost like a mirror).

Basically what I want to know is does the digital signal have an effect on an analog tv thats tuned to that frequency.

While you will see nothing only the normal static if you tune your tv to the uhf channel number, it will basically look like theres nothing broadcasting there.
You can expect some interference to a distant analog tx if there is a local strong dtt signal on the same uhf channel number.
mm

watty

The Digital signal looks a lot like noise to an analog receiver, Satellite or Terrestrial. You might notice a slight change in the character of thre "snow". A signal meter or a voltmenter (multimeter) on the internal tTuner head AGC line might see a small change.

Essentially Digital Receivers can't "see" AM or FM video and FM (analog Satellite) or AM (analog Terrestrial video) can't see Digital.

YOu need a DTT/Free view box to really even know ther is a signal.

lawhec

It is impossible to judge a digital terrestial singal with and analogue tuner. If the DTT channel ia locally free from an analogue signal of the same frequency locally (or any plausible signal from a distant transmitter) trying to tune a DTT signal into an analogue tuner will give the appearence of nothing at all being there. If there is a watchable analogue picture and a digital terrestial signal appears on the same frequency the resultant "interference" is that the analogue signal looks to be weaker - all this depends on how strong or weak the two conflicting signals are. A strong analogue signal will be only marginally affected by a weak digital signal on the same channel, maybe making the piture have some snow, but a weak analogue signal can get totally wiped out by a reasonably strong digital signal on the same frequency. This caused problems in some parts of Omagh which before DTT relied on Holywell Hill for RTÉ. The introduction of DTT test transmissions to Brougher Mountain used the same allocated channels as that for analogue TV from Holywell Hill and to paraphrase the Fat Boys, "hee hee hee hee heeee, WIPEOUT!" with locals complaining to local councillers etc. - this meant DTT was delayed from Brougher Mountain for several months after the tests while RTÉ viewers in Omagh that were affected had to use a different TX at their own expense. Today this means reliable RTÉ reception of Holywell Hill isn't possible south of Newtownstewart while "fringe" DTT reception from Brougher Mt. isn't really possible more than a few miles north of Omagh unless you are lucky enough to be somewhere in the Sperrins which has a good view of Brougher and your sight to Derry is blocked.

egal

Yes.

I am one of those people living in Omagh who was affected in the way described by Northern Correspondent above. A few of those living near here have switched to Longford over the past year or so. However, I am hesitating to do this in case digital transmissions start from Strabane in the near fiture and I find myself back to square one.

Anyone got any thoughts on this?

lawhec

Originally posted by egal
Yes.

I am one of those people living in Omagh who was affected in the way described by Northern Correspondent above. A few of those living near here have switched to Longford over the past year or so. However, I am hesitating to do this in case digital transmissions start from Strabane in the near fiture and I find myself back to square one.

Anyone got any thoughts on this?

Currently the only DTT transmitter that was part of the 87 planned in the UK still to be switched on is Fremont Point in Jersey (thanks to Anglo-French disagreements) and of all the others that have been switched on the priority has been to equalise all the ERPs from the multiplexes from the same site, and to be able to broadcast these multiplexes with as high as an ERP as possible without affecting analogue services.

As 49 of the 50 main TX's have now been upgraded to digital (though not everyone who receives an analogue service from a main TX can receive it's digital services due to either low power of some multiplexes and/or different directional properties for analogue & digital services) along with some important relays, it's logical to think that medium powered relays which serve areas that are beyond the service area of a main TX will be next. However nobody knows what plans there are, what they will be or what relays will be upgraded and what frequencies they will use. I guess Strabane will be eventually upgraded to DTT eventually but there are no hard clues as to when that will be and what frequencies and power it will use.

If it is decided that the Strabane relay will use multiplexes within the same aerial group as its analogue channels (B) then they will have little choice but to use the same frequencies as that of Carin Hill in Longford. However Strabanes' analogue transmissions are vertically polarised while Carin Hill is Horizontal. Unlike the Brougher Mt./Holywell Hill situation where both TX's were Horizontal, this would provide some protection.

egal

Many thanks, Northern Correspondent. It's a difficult one, isn't it? We're looking at an outlay of about £200 in order to get a decent signal. I just don't know what to do. Is there any information at all as to when Strabane might go digital?

lawhec

No, none At least the Carin Hill/Brougher set up could be adapted from an old Holywell Hill/Strabane setup in good working order.

The only "safe" way (if it is an option) is to have a new setup for Truskmore (Sligo) with two aerials, VHF for RTÉ1 & Network 2 and UHF for TV3 and TG4. But it would also result in a complete reinstalliation and won't be cheap.

egal

O.K., Northern Correspondent. Once again, many thanks.

trazix

Thanks for the replys to my question over the last week. I

am about 55-60 Km from Limavady and at sea leavel, Until

RTE switched to UHF I could get a perfect picture on the

UK stations but as the two aerials are now connected into

one the Uk ones are a bit grainy (still should have a

strong signal on the big aerial).

Does anyone know What is the range of the DTT transmission
from Limavady.


What is the best mast head amplifier i could buy.

Could i have two connected to one aerial (e.g one for
analogue and one that I could run direct to one tv for
DTT)

Would a signal booster increase my chances of receiving
DTT.

What way are the analogue and DTT singal's polarised, if
they are polarised different do you have to turn the aerial
to receive the signal.


What does TX & ERPs mean.

Originally posted by trazix
Thanks for the replys to my question over the last week. I

am about 55-60 Km from Limavady and at sea leavel, Until

RTE switched to UHF I could get a perfect picture on the

UK stations but as the two aerials are now connected into

one the Uk ones are a bit grainy (still should have a

strong signal on the big aerial).

Does anyone know What is the range of the DTT transmission
from Limavady.


What is the best mast head amplifier i could buy.

Could i have two connected to one aerial (e.g one for
analogue and one that I could run direct to one tv for
DTT)

Would a signal booster increase my chances of receiving
DTT.

What way are the analogue and DTT singal's polarised, if
they are polarised different do you have to turn the aerial
to receive the signal.


What does TX & ERPs mean.

OK, the best thing you can do is get the loan of a "free view" receiver or purchase one where there is a money back guarantee, theres not too many places that will do that.
Alternatively you can buy one and if it doesn't work sell it on at half price to someone who can receive it,indeed I'll buy it off you:)

The net effect of getting a better aerial or mast head amp will be to improve your analog reception anyway which is no bad thing.
You could put a twin aerial up, ie two alligned together pointed to limavady and that might do the job, but without seeing what your picture is like now, it's hard to say.
Expect to spend €300 or more which might be less than the price of a new digibox with ftv card.
I'm sure watty can advise on types of aerial, mast,amps etc, but I got good results down here in wexford with triax gear.

Tx is just shorthand for transmitter and ERP stands for effective(or emmitted) radiated power ie the transmission power of the tx.
mm