DTT Channel Interferance

superdudeman007

This isnt really to do with your signal or DTT but a lot of people use UK freeview boxes in Co Wicklow etc to get free digital channels. When DTT is launched in Ireland, could there be a clash of channel numbers between Wales and Ireland??? If BBC1 Wales and RTE 1 are on the same channel numbers, what would happen to the signal?

Mossy Monk

new thread for this query

sigh

Ulsterman 1690

If BBC1 Wales and RTE 1 are on the same channel numbers, what would happen to the signal?

You would loose the weaker BBC1 signal and ger RTE1 instead

SRB

Similar question asked elsewhere on this board and my reply ....

"If RTE One and BBC1 Wales are both on channel 1, would people on the East Coast receive either of them properly when Irish DTT is launched?"

That's an interesting point you've raised there. One of the DTT boxes I have (Thomson) has inserted the Irish Channels on channels you can't access directly from the remote - you have to go to the channel menu and select it from the channel list rather than say, enter 1 for RTE1. (It's actually given RTE1 the channel number 15361.)

Another box (Philips) has insterted them down the channel list in the 802 onwards slots. My third box, a Nokia, has just replaced BBC1 on 001 with RTE1, BBC2 on 002 with RTE2 and so on. If you press 1 on the Nokia box you now get RTE1, however if you scroll up one channel, BBC1 NI, although the next number in the channel list is still displaying as number 001. BBC1 Wales is next in the list as 001 too.

lawhec

The OP question isn't 100% specific, therefore there could be two scenarios...

1. The frequency that a multiplex from Mt.Leinster and Preseli transmit on is the same - Mossy Monk has summed it up in one sentence. To explain better, quite simply whichever is the stronger of the two signals is more likely to win out however I'm not too sure what the protection margin is for two DVB-T signals, which could render both unusable. I'll need to double check my RRC-06 listings, there was a concern a few years ago when both transmitters were allocated the same frequencies for DTT, but I would have been surprised if they hadn't cleared this up at the conference, at the great risk of destroying each others broadcasts.

2. Signals from both the UK and RoI are received with two different broadcasters e.g. BBC1 and RTÉ1, having the same Logical Channel Number (LCN), which in this case is 1. This would be dependent on the software of the receiver. I would say that such a scenario has not really been tested for UK DTT boxes until right now. Transmitted in the multiplex are identifiers for transmitter, originating transmitter, Network ID, Multiplex owner and a country code. It appears that some boxes which have two seperate channels with a common LCN is storing the channels in a variety of methods, either through scanning, signal strength etc. Setpal STB's had a function whereby if two common LCNs were found, an arrow key could switch between the two of them. Several other STB's simply allocated the first found channel to "1" and put the other at any point "800" onwards. A few simply store them on the first empty LCN slot from "1" upwards. Its an absolute minefield. The only STB that I know (in the UK) that can allow a channel to be renumbered is the Sony one on sale for around £80.

Me thinks as DTT networks build up, software writers will find a way to accomodate this better so that channels with common LCN's can be placed in the user's EPG either themselves or though several fixed methods.

SRB - what model of Thomson STB are you using?

SRB

The Thompson is a DTI2300. The Nokia will label two channels with the same LCN with the expected channel number first and an "alt" second - so I've Channel 4 (NI) and Channel 4 Alt (Wales). Both are listed as 004 in the channel list. With BBC1 NI and BBC1 Wales, which again are both 001, the last one stored will always be the channel you go to if you press 1 on the remote. The Nokia does allow you to re-number channels in whichever order your want.

Emerson

SRB.. I'm guessing you're up around Killiney Hill if you're getting all of these signals at once?

It's a great site for reception of Welsh, NI & Dublin signals

SRB

No, I'm in Portaferry Co Down, don't normally have anything pointed at the Welsh DTT transmitters, was just curious to see what way the box would store channels if it had more than one channel claiming the "1" slot.

tvman

I am using a Panasonic TUC40 and the four channels are placed in positions 1 to 4 after a rescan. BBC1 and 2 are pushed into 101 and 102 with Irish radio etc now 701 to 705. (The Irish DTT channel shown is 53)

The DTT aerials on C.C. - there is only one set and these are positioned facing south to south west only. The analogue aerials point in all directions except to the north east i.e looking towards Scotland. Have a jpeg somewhere, but cannot find it, will post it when I do.

Incidentally the new DTT transmissions are causing problems for viewers using Camlough Tx around Dundalk. I suspect they are blocking out CH4 at least.