Three Rock DTT Interference

Peddyr · 16-02-2007 12:02AM #1

Dear all,

Since the DVB test moved from Three Rock Ch25 to Ch26 I have now lost my BBC stations from Divis Ch26. This seems to be due to the very strong signal on the same channel as Divis from Dublin. As I live in the Isle of Man and have to pay my license fee to the UK, Divis is the only UK(?) transmitter that I can receive. I can also receive transmissions from Clermont Carn (analogue), Three Rock (analogue / DTT) and Kippure (analogue), although I'm not under ROI license fee jurisdiction and therefore don't have to pay.

Does anyone know what I can do to rectify this problem or should I contact the BCI to report the problem?

Would appreciate any suggestions.

Thanks,

Peddyr

watty · 16-02-2007 01:55AM

Complain to Comreg
They manage Spectrum
BCI only licence content

YOu may have to get a new aerial with better side lobe rejection. Can you get Freeview from Belfast?

What about the repeater at Whitehead/Islandmagee at mouth of Belfast Lough? (maybe shilded by Donaghdee and too low power)

Ulsterman 1690 · 16-02-2007 11:52AM

petition your MP to invade Dublin and bomb Three rock

But seriously whatever happened to all those international frequency planning agreements to prevent this sort of thing ?

Is Ireland now a "rouge state" ?

BTW Is Divis not Ch 27 (unless you mean Divis freeview) ?

Mayo Exile · 16-02-2007 01:02PM

As mentioned already in the "DTT in Dundalk" thread in this forum I lost the Divis Mux on 26 because of interference from Three Rock. Especially peeved about this as it had the BBCi channels for extended sports coverage etc. But as I live in the south I probably have no legal grounds for complaint!

But seriously though will the Three Rock test on 26 have to be stopped if people with Freeview in N.I. are getting impaired reception because of this? It would be interesting to know if people in Co. Armagh etc have lost coverage.

lawhec · 16-02-2007 04:04PM

Can you get multiplexes 1 & 2 from Divis, as these are co-channeled with analogue from Three Rock (E29 & E33)?

Antenna · 16-02-2007 04:07PM

Peddyr wrote:

Dear all,

I can also receive transmissions from Clermont Carn (analogue), Three Rock (analogue / DTT) and Kippure (analogue), although I'm not under ROI license fee jurisdiction and therefore don't have to pay.

Peddyr

Do you have more than one aerial combined into one downlead??
i.e. in addition to your one for Divis do you have another aerial installed to receive TV from the Republic and both combined?
If so you probably now need to run seperate downleads and use some A/B switching arrrangement when you want to select either, to avoid this interference with your Freeview.

Mayo Exile · 16-02-2007 04:19PM

Can you get multiplexes 1 & 2 from Divis, as these are co-channeled with analogue from Three Rock (E29 & E33)?

Northern Correspondent, No. Only get Muxes on chs. 23 and 34. The Mux on Ch. 26 used to be the best quality wise (85 to 90%, strength 55%) until 3R kicked in on that channel.

Thought it might be anti-cyclonic conditions at first as my reception has been affected from time to time by this. Only thought it might be 3R interference when the weather went back to "normal" and the Mux on 26 still wasn't there.

John Dough · 16-02-2007 04:25PM

You are probably using a wideband aerial so you will have to swap it for the best group to suit your area as this usually solves the problem..
I passed 'thru Holyhead recently and could not get anything on Freeview while analogue was ok so try tuning to this area.

Peddyr · 17-02-2007 05:22PM

Dear all,

Many thanks for your comments on this issue. I'm using a high gain group C/D X-beam type aerial which is approx at a 90 degree angle to 3R aimed directly at Divis. I'm recieving all freeview muxes on chs 23 / 26 (which was strongest signal from Divis & now gone since 3R moved DVB-H tests from ch25 to ch26) / 29 / 33 / 34 & 48. The signal from 3R is side on to the aerial. To receive 3R signal aerial is rotated 90 degrees to the left (SW direction) and pulls in very good signal (DTT pilot) using UK Freeview box on chs 26 (strongest, DVB-H tests) / 54 (RTE 1&2, TG4, TV3, RTE Radio & Today FM) / 58 (Mux 3) & 61, again Mux 3. This signal is much stronger from 3R than Divis in my location at Cregneash village in the extreme southwest of the Island at an elevation of approx 500ft with good direct line of sight to all Irish transmitters on east coast - Divis, Black Mountain, Clermont Cairn, Three Rock & Kippure (UHF).

I emailed DCMNR & BCI who have suggested I contact ComReg which Watty has also suggested and Ofcom (UK) which is my next move. Out of interest, I have included the replies received from DCMNR & BCI respectively below. Note where it states that there is no Pilot test on ch26!

"Dear Peddyr

I refer to your email to my colleague, Joe Meleady, which was forwarded to me earlier today.

For assistance with your query regarding potential interference between Irish transmissions and your television reception from Divis, please contact ComReg, who are responsible for regulating transmissions in Ireland on 00-353-1-804-9600. ComReg contact details: http://www.comreg.ie/sections/contact.asp?NavID=123&NID=100058

As the Department of Communications, Marine and Natural Resources is running the Pilot, I can tell you that the Pilot does not broadcast on Ch 26 from either broadcast site (Three Rock or Clermont Cairn). Also, there have been no DTT Pilot broadcasts on any channels other than those used when the trial started in August 2006. When we take into consideration the fact that your BBC reception difficulties began only recently, it seems to suggest that the DTT Pilot is not the cause.

Unfortunately, I cannot be of more assistance. If you contact ComReg they should be in a position to provide you with more information on the matter.

Best Regards"

Lorcan Mac Fadden (DCMNR)

"Dear Peddyr

The DVB-H trial was moved from Ch25 to Ch26 as there was a lot of interference being caused to viewers in County Down. Please contact the UK authorities regarding this problem (see Ofcom’s website for contact details).

Regards"

Roger Woods
Senior Executive Engineer
Broadcasting Commission of Ireland

DMC · 17-02-2007 05:50PM

The department correspondence is correct that the DTT trial, being administered by his department, isn't on Channel 26, but the Comreg administered DVB-H (handheld) trial for TV on mobile phones and handheld devices is on channel 26, which is a separate and not connected trial. Not sure if its O2 or 3 that are doing it on that channel...

Antenna · 17-02-2007 05:58PM

Peddyr wrote:

I'm using a high gain group C/D X-beam type aerial which is approx at a 90 degree angle to 3R aimed directly at Divis.

You are using the wrong aerial (C/D, which is for Ch48 and above)

It should be a Group K (21-48) or W (all UHF) for the 'Divis' channels
On the low channels the aerial is going to have more pickup off-beam!!!

look here for aerial groups

http://www.bbc.co.uk/reception/analogue_tv/anatv_aerials.shtml

Peddyr · 17-02-2007 06:10PM

Antenna wrote:

You are using the wrong aerial (C/D, which is for Ch48 and above)

It should be a Group K (21-48) or W (all UHF) for the 'Divis' channels
On the low channels the aerial is going to have more pickup off-beam!!!

look here for aerial groups

http://www.bbc.co.uk/reception/analogue_tv/anatv_aerials.shtml

I was using this aerial originally for analogue TV from CC but as it picks up all DTT from Divis & 3R perfectly I just left it in use. Would wideband aerial reduce offset interference?

Mayo Exile · 19-02-2007 05:25PM

Comreg administered DVB-H (handheld) trial for TV on mobile phones and handheld devices is on channel 26

Just wondering DMC, are ComReg allowed to use this Channel (26) for the DVB-H trial? Surely they must know one of the Divis Muxes is already there and might cause interference when they know they have switched from Ch. 25 for causing interference already??!!! Maybe its the Benagh relay (UTV is on 25) thats being interfered with? I think its near Kilkeel. Cushendun in Co. Antrim also has Channel 4 on 25. But that would probably be too far north to suffer interference.

watty · 19-02-2007 06:01PM

Belfast & Dublin far enough apart for "normal" reception to use same Channels. As is Longford & Scotland.

DMC · 19-02-2007 06:41PM

And factor in polarisation... I wonder how you could quantify handheld reception as H or V ?

lawhec · 19-02-2007 07:23PM

Three Rock is cleared to use E26 for DVB-T, and I'd assume DVB-H too.

mrdtv · 22-02-2007 09:19PM

Welcome to the future. DVB-H signals are usually transmitted vertically and they have a far higher signal strength than DVB-T transmissions. See the OFCOM report on 'hole punching'from DVB-H into DVB-T: its on their web site for December. It was done by Aegis Systems. under the DSO report released 19th December 2006. This is an example of DX hole punching.

mrdtv

watty · 23-02-2007 12:16AM

Mobile phone antennas use H AND V diversity aerials to allow for variation. Any car mobile radio system uses Vertical or at worst slant polarisation.

If a transmitter used circular polariasation, the receiver will work at any angle , but with a 50% power loss penalty. I'd use circular for DVB-H

John Dough · 26-02-2007 10:07PM

Peddyr wrote:

I was using this aerial originally for analogue TV from CC but as it picks up all DTT from Divis & 3R perfectly I just left it in use. Would wideband aerial reduce offset interference?

I would not do anything yet my friend as 3R is using 10Kw power now and Divis is only using 3Kw as this will be increased when the analogue signal is switched off in 2012 and you should have it all back ,or in the meantime get a wideband aerial and try that.

Richard · 27-02-2007 12:41AM

Ulsterman 1690 wrote:

But seriously whatever happened to all those international frequency planning agreements to prevent this sort of thing ?

I suppose that it isn't intended for him to receive DTT yet as it hasn't officially reached the IOM. I presume that when it does it'll be broadcast from Isle of Man transmitters rather than from the UK.

Given that the IOM is an outpost of the Border ITV region, does that mean that analogue switch-off will take place there at the same time as England and Scotland or is it exempt because it's not in the UK?

Is Ireland now a "rouge state" ?

Is it red?:D

Mayo Exile · 08-03-2007 02:23PM

Could anybody recommend an aerial to reject the signal from 3R on channel 26 and restore my Divis MUX reception or is this impossible?

Ulsterman 1690 · 08-03-2007 03:36PM

look for a high "front to back ratio" in the specs

If you can site the antenna so that its shielded (by a wall, tree, etc) in the direction of Three rock but not Divis that may also help

Mayo Exile · 08-03-2007 04:01PM

Originally posted by Ulsterman 1690: look for a high "front to back ratio" in the specs

Thanks for that U 1690! What type of aerial would be the best for this? Directional, BB Grid etc?

championc · 13-03-2007 10:30PM

So now I know what happened to my BBC2 from Divis. I live in Ballinteer, Dublin, in the shadow of 3R. I have happily had all of my BBC's and ITV's from Divis since the early 90's until a few weeks ago when the BBC2 reception became awful. BBC2 is on Ch27 so the strength of the DVB signals on Ch26 has killed me completely. Somehow I don't think I want to have to wait until 2012 before the Analog in Divis is turned off !!!

C

byrnefm · 13-03-2007 11:27PM

championc wrote:

Somehow I don't think I want to have to wait until 2012 before the Analog in Divis is turned off !!!
C

Don't worry, the trial ends around August 2008. Then we'll probably have another five year gap until the next trial, so you'll be ok until then :rolleyes:

championc · 14-03-2007 12:59AM

I can't really see them leaving all the kit just lying there gathering dust. My guess is that it's here to stay and is just a matter of the partipitation level by broadcasters. And what's the bets that the big thing next Christmas will be TV's with integrated "freeview" decoders which will then be "capable" of picking up 10's of channels - albeit with the help of an additional external decoder.

C

Three Rock DTT Interference

Comments