TV transmitters in NI post DSO

Glenelly My Home · 07-10-2010 02:51PM

lawhec wrote: »

All main transmitters and relay stations in Northern Ireland (from the provisional list currently on Digital UK's website) will remain in service post-DSO in Northern Ireland. Unlike however in the south and across the Irish Sea, no new transmission sites are planned.

All transmitter and relay sites will not require an aerial switch come DSO to receive all services except Plumbridge, which is changing from Group C/D to Group B.

Plumbridge is a small relay just outside the village of the same name, serving a part of the Glenelly Valley in the Sperrin Mountains that is shielded from the Strabane relay (there is another relay station a few miles east, funnily enough called "Glenelly Valley" near the village of Cranagh), RTÉ there, at least on VHF, can be received from Truskmore though I'm not sure how reliable UHF is. Anyway, the reason for such an awkward change is that presently two of the four frequencies used at Plumbridge lie above E62. The draft plan was to use a new frequency at E48 (along with E52 and E56) but now they plan to use E50 for the BBC-A multiplex, E46 for the UTV/C4 multiplex and E43 for the HD multiplex.

What does that mean for Glenelly Valley?
This is where I live.

Sam the Aerialman · 07-10-2010 07:26PM

Glenelly My Home wrote: »

What does that mean for Glenelly Valley?
This is where I live.

You're fine they've just upgraded Glenelly Valley from it's pole to a tower and moved the logs.

Sam the Aerialman · 07-10-2010 07:33PM

lawhec wrote: »

Killowen Mtn.'s function isn't solely to feed Kilkeel (though that is it's primary purpose), I'd assume some viewers take a feed directly off it as it has a reasonable ERP for a relay as well, also other "link" relays in Britain have been or are planning to be converting as well.
The allocations on the Digital UK website are a "latest update", they have changed from around a year or two ago at some relay sites.

Killowen's only function is to put a signal into Kilkeel they are infact putting an SHF chain in place to feed Kilkeel.

An SHF chain to Kilkeel is required because the relayed signal from Killowen Mountain would fall outside the guard interval, with respect to the 'direct' signal from Divis.

The guard interval for the post-DSO UK modes of DVB-T and DVB-T2 is 28
microseconds (1/32 of 896us for DVB-T, 1/128 of 3.684ms for T2). Speed of
light is 300,000 km/s so it travels 8.4km in 28us.

As the crow flies, Divis to Kilkeel is about 57.2 km; Divis to Killowen 58.2
km, and Killowen to Kilkeel 7.2km. The difference is 8.2km, or about 27.3
us. That's a bit close.

Kilkeel certainly doesn't have line-of-sight from Divis, but we all know RF
is a black art and people get what they shouldn't be able to (and also,
don't get what they should).

At 64QAM 2/3, 1/32 gives a usable data rate of 24.13 Mbit/s, while 1/4 gives
a data rate of 19.91 Mbit/s. That's a pretty big drop in bitrate - I haven't
seen any sign of this being proposed anywhere. Ofcom's 'Reference
Parameters' says they should be using 1/32 after DSO, though it does say
they can use something different with the written consent of Ofcom.

lucernarian · 07-10-2010 07:43PM

Can Kilkeel receive any signal from Divis with the extensive Mourne Mountains in the way? Also, is a SHF chain the equivanent of what would be also referred to as a "microwave link"? Where are you getting this info from?

I know that Killowen Mtn. uses very directional tx and rx aerials and that over about 5 miles the 150W peak EIRP would give a very adequate signal at Kilkeel but nothing excessive by any means.

Sam the Aerialman · 07-10-2010 10:26PM

To_be_confirmed wrote: »

Can Kilkeel receive any signal from Divis with the extensive Mourne Mountains in the way? Also, is a SHF chain the equivalent of what would be also referred to as a "microwave link"? Where are you getting this info from?

I know that Killowen Mtn. uses very directional tx and rx aerials and that over about 5 miles the 150W peak EIRP would give a very adequate signal at Kilkeel but nothing excessive by any means.

Kilkeel has no line of sight of Divis whatsoever. An SHF chain is exactly that, it differs were a microwave link is point to point. A chain is point to point but is single frequency doesn't require any isolation between the Tx and Rx and can pass on using a baseband amp and a few line pre-amps.

Yes Killowen uses trough type aerials which are 4 stacked bow tie style dipoles phased into a harness, the aerials are made up of a backing plate and a GRP membrane. The rx feed at Killowen is one single horizontal trough which is fed on 7/8 feeder and split 4 ways into a blue streak bbc unit. Each channel is modulated, has specially designed units to stop channel fading combined and put out onto two vertical troughs. Killowen is essentially a spotlight that rains down on Kilkeel. The two structures are isolated and opposite pol so the rx doesn't wipe out the tx are fade into the frequencies. The system was cutting edge when the beeb put her into service will be sad to see the system go but technology moves on.

Sam the Aerialman · 07-10-2010 10:56PM

watty wrote: »

You don't have a picture of what is INSIDE the box?

No but i do have something similar.

http://s663.photobucket.com/home/AerialServices/allalbums

lawhec · 08-10-2010 04:46PM

Glenelly My Home wrote: »

What does that mean for Glenelly Valley?
This is where I live.

It'll only affect you if you are currently receiving BBC1, BBC2, UTV and Channel 4 from the Plumbridge relay. If you are receiving BBC1 on a frequency displayed on your TV as either 52, E52, C52, 719.25MHz or 719MHz then that'll be Plumbridge.

However the frequency allocations are not yet final and are subject to change.

There's two relays serving the Glenelly Valley area, doesn't help that one of them is called "Glenelly Valley" as that might seem to cover all of it! The Glenelly valley relay lies about a mile south-west of Cranagh on the Corramean Road, while the Plumbridge relay is about 3/4 mile south east from the village centre just off the Landahussy Road.

egal · 08-10-2010 07:44PM

lawhec, why do you feel the need to have that offensive icon in your posts? Would you not consider replacing it with something less salacious? Please?

Mike 1972 · 08-10-2010 11:43PM

Surely it would be better to PM the guy (or a Mod) if youre that concerned ?

Although IMO describing some of the more dubious aerial contractors out there as "sharks" is fair comment really

lucernarian · 08-10-2010 11:47PM

Sam the Aerialman wrote: »

Kilkeel has no line of sight of Divis whatsoever.

I wasn't talking so much about LOS, I was referring to signal strength itself. The signal from Divis must be more than negligible if guard intervals are an issue for Kilkeel and Killowen Mountain.

As for SHF, my question is more fundamental. I assume it's based on microwave technology, i.e. super-high frequency? So why then has Killowen Mountain been assigned DSO frequencies if it's no longer going to be used? I get the feeling it's because Digital UK haven't figured out their plan for Northern Ireland yet.

Peter Henderson · 09-10-2010 12:40AM

Kilkeel certainly doesn't have line-of-sight from Divis

and the reason for that is a dirty great big lump of granite called the Mournes Sam. I think Thomas's Mountain and Slieve Donard are the ones that primarily get in the way (i.e. where they sweep down to the sea !).

It' s quite interesting listening to VHF radio in that region as you drive from Kilkeel through Annalong to Newcastle. Take 96.7 for example. In the Kilkeel/Annalong areas, you get Lyric FM from Three Rock. As you drive around the coast it disappears, somewhere around the Bloody Bridge/Maggie's Leap, to be all of a sudden replaced with Belfast Citybeat. I would imagine digital TV will be something similar.

I wonder how good Newcastle is re. line of site to Divis ? The Newcastle transmitter will be Freeview Lite post DSO, but just looking around the town I have noticed some quite large aerials pointing towards Divis. Can you receive Freeview at present in Newcastle ? Can you get the digital TV tests from Three Rock in the Kilkeel/Annalong area ?

Sam the Aerialman · 10-10-2010 01:20AM

To_be_confirmed wrote: »

I wasn't talking so much about LOS, I was referring to signal strength itself. The signal from Divis must be more than negligible if guard intervals are an issue for Kilkeel and Killowen Mountain.

As for SHF, my question is more fundamental. I assume it's based on microwave technology, i.e. super-high frequency? So why then has Killowen Mountain been assigned DSO frequencies if it's no longer going to be used? I get the feeling it's because Digital UK haven't figured out their plan for Northern Ireland yet.

If you want to talk fundamentals first law is tv signals travel in straight lines, Tx's are in the unique position that they must have line of sight to a transmitter and be in an ideal position to cover it's target area. Minimum requirements for a usable rx feed is in and around 87db, remember that the signal must be split 4 ways and separated hence why line powered amps are used. Most tx's are in use due to ghosting, when we get DTT coverage in full any multipath problems are gone but with the legacy of aerials i do believe they will switch every relay currently in use. In Northern we're in a rather unique position were we are an island. Meaning any inland transmitters can't see the radio horizon, we have lots of coastal tx's as a result.

Guard intervals are only in use in COFDM not in analogue meaning there is no encoding, someone mentioned it's much more expensive to rx off air dtt signals. The reason is simple the "bits of information" need encoded and in order to do that OEM boards are built into the 19inch units. I know the cost of self help gear so lord knows what broadcast quality gear costs per frequency. The problems with Kilkeel and Killowen have nothing to do with the guard interval it's to do the bit rate, if there's a delay in signal on analogue you get ghosting in DTT with the digital cliff you get F all.

It's SHF Microwave technology, probably a 4 dish point to point distribution system with a PC and an encoder at one end i would imagine. Killowen was issued DSO allocations just as every Tx in the land was, they're co-channel Divis PSB's so if they're not used it hardly matters. They keep chirping that same line "The plan for Northern Ireland has not been locked down" We're the only part of the UK who hasn't even seen a version 1 frequency plan from Ofcom.

Sam the Aerialman · 10-10-2010 01:35AM

I wonder how good Newcastle is re. line of site to Divis ? The Newcastle transmitter will be Freeview Lite post DSO, but just looking around the town I have noticed some quite large aerials pointing towards Divis. Can you receive Freeview at present in Newcastle ? Can you get the digital TV tests from Three Rock in the Kilkeel/Annalong area ?[/QUOTE]

Yes you can get reasonable Freeview in Newcastle, some problems are the early morning/ evening when the temperature lowers and the dew sets in.
The mountains can build up a lot of moisture in the air.

Newcastle Tx has perfect Line of Sight to Divis, only requires a fairly low trough aerial to receive off air. I suspect the trough was employed because they felt logs would rust much to quickly. I often wonder if they got the skew of the tx aerials wrong when they commissioned Newcastle, has altered several times over the years for unknown reasons.

reboot · 10-10-2010 01:29PM

lawhec wrote: »

Of course, parts of the Co. Down and Co. Antrim coasts might be able to get services from Britain and IoM TX's the same way cross-border transmissions carry in Ireland.

As mentioned a few times on the thread IOM due to transmit HD 9 days from now.

Peter Henderson · 10-10-2010 06:52PM

By the way, anyone know what's happening to Northern Visions TV (Belfast's local TV station) post DSO ?

I did e-mail them a while back and was told they were in negotiations with Ofcom in order to secure a slot on Freeview.

Sam the Aerialman · 10-10-2010 08:03PM

Peter Henderson wrote: »

By the way, anyone know what's happening to Northern Visions TV (Belfast's local TV station) post DSO ?

I did e-mail them a while back and was told they were in negotiations with Ofcom in order to secure a slot on Freeview.

I'll be honest with you i can't see them surviving. I did an "MB21" reccy up to their site at Ballygomartin, was having the wrecking ball treatment. They were broadcasting from one of the old towers on a former MOD site downhill from Divis. Are they still on air and if so were did they go?

The cost implications for smaller community stations is going to be beyond their reach, i don't know if any of you followed how difficult it was for Channel M to get clearance to use the interleaved mux at Winter Hill. Even then they got a low power setup at the base of the mast.
Arqiva have stipulated in reference documents fees and charges for site usage, site rental and maintenance mounting to tens of thousands pounds per annum. They only want their sites used (in this case Divis) The bandwidth will be sold to the highest commercial bidder.

Mike 1972 · 10-10-2010 11:07PM

Peter Henderson wrote: »

By the way, anyone know what's happening to Northern Visions TV (Belfast's local TV station) post DSO ?

I did e-mail them a while back and was told they were in negotiations with Ofcom in order to secure a slot on Freeview.

Ive often wondered about this myself (likewise Channel 9 in L/Derry) A lot of UK mainland RSL's have thrown in the towel already and called a day. On the other hand over in the US LPTV's were allowed to keep their (analogue ) signals on the air even after all the full power stations had to keep theirs off.

Ive always thought it was the height of stupidity putting an analogue relay of TG4 on from Divis for various reasons among them the fact that the same amount of spectrum could have been used for an additional DTT multiplex carrying TG4, NVTV, and the RTE channels (including radio)

lucernarian · 10-10-2010 11:19PM

Sam the Aerialman wrote: »

If you want to talk fundamentals first law is tv signals travel in straight lines, Tx's are in the unique position that they must have line of sight to a transmitter and be in an ideal position to cover it's target area. Minimum requirements for a usable rx feed is in and around 87db, remember that the signal must be split 4 ways and separated hence why line powered amps are used. Most tx's are in use due to ghosting, when we get DTT coverage in full any multipath problems are gone but with the legacy of aerials i do believe they will switch every relay currently in use. In Northern we're in a rather unique position were we are an island. Meaning any inland transmitters can't see the radio horizon, we have lots of coastal tx's as a result.

Guard intervals are only in use in COFDM not in analogue meaning there is no encoding, someone mentioned it's much more expensive to rx off air dtt signals. The reason is simple the "bits of information" need encoded and in order to do that OEM boards are built into the 19inch units. I know the cost of self help gear so lord knows what broadcast quality gear costs per frequency. The problems with Kilkeel and Killowen have nothing to do with the guard interval it's to do the bit rate, if there's a delay in signal on analogue you get ghosting in DTT with the digital cliff you get F all.

It's SHF Microwave technology, probably a 4 dish point to point distribution system with a PC and an encoder at one end i would imagine. Killowen was issued DSO allocations just as every Tx in the land was, they're co-channel Divis PSB's so if they're not used it hardly matters. They keep chirping that same line "The plan for Northern Ireland has not been locked down" We're the only part of the UK who hasn't even seen a version 1 frequency plan from Ofcom.

I didn't want to talk fundamentals per se, I just wanted to know what the SHF chain was in a basic sense (I hadn't previously heard of SHF). Thanks for that. Also, why did you mention guard intervals previously if the problems with Kilkeel and Killowen have nothing to do with guard intervals? I've done my bit of physics in college, so radio waves travelling in straight lines isn't lost on me. But nor is the quirks of propagation where I can receive decent analogue from Divis despite the Cooley Mountains being in the way. I'll put it this way, what's the main reason for a SHF chain being provided for Kilkeel rather than continuing the active deflector setup at Killowen Mountain? And if a SHF chain will be used, does that mean that Killowen Mountain will cease broadcasting on UHF by 2013 after all?

reboot · 14-10-2010 02:41PM

Sam the Aerialman wrote: »

I wonder how good Newcastle is re. line of site to Divis ? The Newcastle transmitter will be Freeview Lite post DSO, but just looking around the town I have noticed some quite large aerials pointing towards Divis. Can you receive Freeview at present in Newcastle ? Can you get the digital TV tests from Three Rock in the Kilkeel/Annalong area ?

Yes you can get reasonable Freeview in Newcastle, some problems are the early morning/ evening when the temperature lowers and the dew sets in.
The mountains can build up a lot of moisture in the air.

Newcastle Tx has perfect Line of Sight to Divis, only requires a fairly low trough aerial to receive off air. I suspect the trough was employed because they felt logs would rust much to quickly. I often wonder if they got the skew of the tx aerials wrong when they commissioned Newcastle, has altered several times over the years for unknown reasons.[/QUOTE]
I gave a friend a set top (amplified) aerial,he lives at the Annalong end of Newcastle,Divis Freeview is not a problem,but I suppose he may be lucky in that the Sharpe Aquas Tele appears to have a good tuner.

Digifriendly · 14-10-2010 07:07PM

Out of interest my parents have just moved into a nursing home in Newtownards and they wanted a new flatscreen TV for their room. I bought a 22" Sony idtv and got it tuned in. While there is a relay for Newtownards most of the town seems to have aerials for Divis. The analogue tuner not surprisingly did not pick up Five but BBC1/2/UTV/Channel 4 were fine. When the Digital tuner finished scanning Multiplex C (no Sky News) was missing as well Multiplex D (no ITV4).

SRB · 15-10-2010 12:15PM

The relay is there for the part of the town in Scrabo's Shadow, Divis is used by the rest of the town. CH 5 isn't on the relay, nor are any DTT services. If they are picking up DTT while pointed at the relay, the home could try pointing their aerial at Divis instead.

Digifriendly · 15-10-2010 06:22PM

SRB wrote: »

The relay is there for the part of the town in Scrabo's Shadow, Divis is used by the rest of the town. CH 5 isn't on the relay, nor are any DTT services. If they are picking up DTT while pointed at the relay, the home could try pointing their aerial at Divis instead.

Thanks very much for that. The channel nos on the TV Tuner menu indicated the analogue signal was from Divis as well as the Freeview signal but obviously signal not strong enough to bring in analogue Five or 2 of the multiplexes on DTT.

SRB · 16-10-2010 02:25PM

Five comes from Black Mountain, so is possibly totally shielded at the home's location - Divis DTT also requires a lesser spotted group K, the home may be using a Group A, which is the analogue "Divis Aerial" group.

Digifriendly · 16-10-2010 09:18PM

SRB wrote: »

Five comes from Black Mountain, so is possibly totally shielded at the home's location - Divis DTT also requires a lesser spotted group K, the home may be using a Group A, which is the analogue "Divis Aerial" group.

You may well be right there as Group A would rule out Multiplex C (ch. 48) and isn't multiplex D weaker compared to the other ones?

Peter Henderson · 17-10-2010 01:07AM

SRB wrote: »

The relay is there for the part of the town in Scrabo's Shadow, Divis is used by the rest of the town. CH 5 isn't on the relay, nor are any DTT services. If they are picking up DTT while pointed at the relay, the home could try pointing their aerial at Divis instead.

Channel 5 will be on the relay after DSO, although the relay will be Freeview Lite.

I would have thought Freeview from Divis in Newtownards would have been quite difficult since the town is in a bit of a dip and shielded by other hills, other than Scrabo. It might be OK after DSO though, when Divis has a dramatic power increase.

Five comes from Black Mountain, so is possibly totally shielded at the home's location - Divis DTT also requires a lesser spotted group K, the home may be using a Group A, which is the analogue "Divis Aerial" group.

I would imagine that might be the case SRB. An upgrade to a wideband aerial might solve the problem.

Digifriendly · 17-10-2010 08:56PM

Peter Henderson wrote: »

Channel 5 will be on the relay after DSO, although the relay will be Freeview Lite.

I would have thought Freeview from Divis in Newtownards would have been quite difficult since the town is in a bit of a dip and shielded by other hills, other than Scrabo. It might be OK after DSO though, when Divis has a dramatic power increase.

Interestingly I bought the TV for my parents in a shop in Newtownards and I was told there that Freeview was available for most in the town and that the only difficult area was that just below the hill between N'ards and Belfast. The aerials on the Movilla road where the nursing home is and the immediate area seem mostly to be aiming at Divis (horizontal polarisation) rather than the local relay (vertical polarisation) but I haven't looked at other parts of the town.

SRB · 18-10-2010 08:07PM

Digifriendly wrote: »

Interestingly I bought the TV for my parents in a shop in Newtownards and I was told there that Freeview was available for most in the town and that the only difficult area was that just below the hill between N'ards and Belfast. The aerials on the Movilla road where the nursing home is and the immediate area seem mostly to be aiming at Divis (horizontal polarisation) rather than the local relay (vertical polarisation) but I haven't looked at other parts of the town.[/QUOTE

Yup, hence the relay. The Movilla Road should be OK, I know a few people in the dip just out the Movilla Road and they have all Muxes. It could well be the "Group A" issue.

Sam the Aerialman · 21-10-2010 12:34AM

To_be_confirmed wrote: »

I didn't want to talk fundamentals per se, I just wanted to know what the SHF chain was in a basic sense (I hadn't previously heard of SHF). Thanks for that. Also, why did you mention guard intervals previously if the problems with Kilkeel and Killowen have nothing to do with guard intervals? I've done my bit of physics in college, so radio waves travelling in straight lines isn't lost on me. But nor is the quirks of propagation where I can receive decent analogue from Divis despite the Cooley Mountains being in the way. I'll put it this way, what's the main reason for a SHF chain being provided for Kilkeel rather than continuing the active deflector setup at Killowen Mountain? And if a SHF chain will be used, does that mean that Killowen Mountain will cease broadcasting on UHF by 2013 after all?

I apologise i wasn't aware you had never heard of SHF transmissions. They generally occur over 3.51 Ghz frequencies and are handy for a point to point UHF link. A standard RBL is only so good were it all comes down to field strength but tidal fading and sea paths can push out the polarisation.
Rumster - Keelylang - Fair Ilse - Bressay is about the best known way this form of point to point link operates, it's also a much cheaper way of getting multiple feeds to a Tx site, feeds were logs and various troughs had to be employed.

I brought up guard intervals because written into OFCOMs own principals and guidelines for DSO that all all transposers and active deflectors much operate a guard interval of 1/32. That won't be possible at Killowen because of the distances involved and they cause a drop in bit rate. Not ideal when the primary source of that transmission is to feed a transposer, that wouldn't equate to a clean feed. You must remember that only two of these experimental type stations exist the other is Bethesda, it was not designed to cope with such distance calculations. In fact i believe and have done for many years that Killowen was done simply done by the Beeb to prove it could be done. A simple transposer would of sufficed, the frequencies were all co-channel so it made little difference in such an isolated part of the world.

watty · 21-10-2010 07:26PM

1GHz upwards is Microwave..

Above 200GHz is Magic.

SHF is vaguely above UHF in Microwaves. It's an ITU type designation

When I worked in BBC Comms we used SHF or Microwave to refer to same thing. I used to service some.

Microwaves often split as L, S, C, X, Ku, K, Ka etc... Radar Designations
L Band is Satellite IF as well as 1st Microwave Band, about 1GHz to 2GHz.
S Band is up to about 3GHz
C band up to about 4.5GHz
Nowadays X is 8 to 10.7
and Ku is 10.7 to 12.6

The Bands are not really exact.

reboot · 26-02-2011 10:33AM

lawhec wrote: »

Of course, parts of the Co. Down and Co. Antrim coasts might be able to get services from Britain and IoM TX's the same way cross-border transmissions carry in Ireland.

Receiving IOM Freeview full strength in S.Down on New Freeview Bravia,But no apparent sign of HD transmissions.What should I be looking for?

TV transmitters in NI post DSO

Comments