DTT Mt Leinster, Ch45 blocking Presely in the South East

olliewexford

The Cush wrote: »

Here are some links to information I posted previously about frequency allocations.
http://www.boards.ie/vbulletin/showthread.php?p=63482487#post63482487
http://www.boards.ie/vbulletin/showthread.php?p=63330193#post63330193
http://www.boards.ie/vbulletin/showthread.php?p=63090864#post63090864
http://www.boards.ie/vbulletin/showthread.php?p=63081189#post63081189
http://www.boards.ie/vbulletin/showthread.php?p=59890026#post59890026

thanks for the links, i got a good grasp of the arrangement they have in place, thanks

Satdog

Anyone know the current situation with Mt Leinster? Ch 39 seems to have gone and I'm getting a lot of pixelation on Chs 42,45 and 49 - the signal quality for these channels is good but picture quality is only showing as poor. Co channel interference with Preseli methinks which wasn't a problem with Ch 39.

The co channel shouldn't affect your actual reception as with dtt,you either have it decoded or you don't.
I'd guess the lower power,poorer quality and lack of ch39 has more to do with recent weather damage up there than anything else.

This of course begs the question...why are they testing at lower power with faulty equipment if thats the case? Why not switch it off untill one of the muxes are needed and of course power up ch39...

mrdtv

Deleted User wrote: »

The co channel shouldn't affect your actual reception as with dtt,you either have it decoded or you don't.
I'd guess the lower power,poorer quality and lack of ch39 has more to do with recent weather damage up there than anything else.

This of course begs the question...why are they testing at lower power with faulty equipment if thats the case? Why not switch it off untill one of the muxes are needed and of course power up ch39...

Because like any public service quango they think they can burn licence fee payers money. I note with interest a) the lack of a positive statement from OneVision and b) the downgrading of Ireland's economic position on Moody's, EU gilt markets etc today. Talk about fiddling while the economy falls apart. On a purely realistic basis they should run with E39 to provide a test service and reduce operating costs. Cathal Goan & Co need to demonstrate that they are not asleep at the wheel...

marclt

Ch39 Off... Really!? Boo-hiss... and I've a shiny new aerial arriving too!

Still, conditions at Mt.L were especially poor during the last few weeks... but falling ice was the latest issue to disrupt transmissions. I think they managed to keep the lights on!

marclt

Just received a Fracarro Sigma HD aerial. Haven't had a chance to get outside to install properly, so set it up and pointed it outside the window. Was able to get RTENL on Ch.39 here.

So it is back on. Obviously can't get 42, 45 or 49 due to my proximity to Preseli.

mrdtv

marclt wrote: »

Just received a Fracarro Sigma HD aerial. Haven't had a chance to get outside to install properly, so set it up and pointed it outside the window. Was able to get RTENL on Ch.39 here.

So it is back on. Obviously can't get 42, 45 or 49 due to my proximity to Preseli.

Because it is a clear channel and that is a very good compact antenna from Fracarro. How much did you pay for it? BTW another article suggests, rightly, that the use of log-periodics is the way to go to reduce CCI in the digital era citing the well known CCI problem between Ilfracombe and Carmel where there is CCI on three muxes. I'll post a link for that later. Certainly there are new logs with built in amps and they do have very good sidelobe protection. Perhaps you should fix the Sigma on a rotor.

Things will hot up again next month when Blaen-Plwyf starts 40kW DTT on February 10th and it will be the first DVB-T2 station in Wales from March 10th also on 40kW.

Satdog

marclt wrote: »

Just received a Fracarro Sigma HD aerial. Haven't had a chance to get outside to install properly, so set it up and pointed it outside the window. Was able to get RTENL on Ch.39 here.

So it is back on. Obviously can't get 42, 45 or 49 due to my proximity to Preseli.

Chs 39 and 49 appear to back on in full. I tried manualy tuning in Chs 42 and 45 but got nothing from either Mt Leinster or Preseli. Is Mt Leinster still broadcasting a strong signal (but no sound or pictures) that is blocking these channels from Preseli? I don't have the equipment to test this.

Sam Russell

mrdtv wrote: »

BTW another article suggests, rightly, that the use of log-periodics is the way to go to reduce CCI in the digital era citing the well known CCI problem between Ilfracombe and Carmel where there is CCI on three muxes. I'll post a link for that later. Certainly there are new logs with built in amps and they do have very good sidelobe protection. Perhaps you should fix the Sigma on a rotor.
.

The log periodic aerial has a better group delay characteristic than a yagi, which might be better for digital signals. Logperiodics are naturally broadband, whereas a yagi is a tuned antenna. However, the mux bandwidth is only 8 mhz, so it probably does not matter, but CCI performance/behaviour could be different.

FWIW.:)

Satdog

Satdog wrote: »

Chs 39 and 49 appear to back on in full. I tried manualy tuning in Chs 42 and 45 but got nothing from either Mt Leinster or Preseli. Is Mt Leinster still broadcasting a strong signal (but no sound or pictures) that is blocking these channels from Preseli? I don't have the equipment to test this.

Both 39 and 49 are on much higher power for the past few days.
39 should be easily receivable by marc in wales now.

49 mt leinster may be interfering with Presely reception in wales with the power it's currently on as thats a low power presely mux.

marclt

Deleted User wrote: »

Both 39 and 49 are on much higher power for the past few days.
39 should be easily receivable by marc in wales now.

49 mt leinster may be interfering with Presely reception in wales with the power it's currently on as thats a low power presely mux.

Well all was fine, till I added it to the array on the mast. Now, I think it is going to require a little more tinkering!

MRDTV... got it on ebay, for a steal! Very good price....

presely 42 is no longer blocked here this evening.
E4,five usa,quest etc are all coming in here fine.

Is presely 42 on higher power or is mt leinster 42 on lower power or switched off?

marclt

Deleted User wrote: »

presely 42 is no longer blocked here this evening.
E4,five usa,quest etc are all coming in here fine.

Is presely 42 on higher power or is mt leinster 42 on lower power or switched off?

There is a bit of a lift - pulling in signals from the east/south east - noticed it this evening. So it could be that.

Barely a signal on 39 for me this evening. So it could be that some changes are being made.

Gerry Wicklow

marclt wrote: »

There is a bit of a lift - pulling in signals from the east/south east - noticed it this evening. So it could be that.

Barely a signal on 39 for me this evening. So it could be that some changes are being made.

Presely 42 and 45 have been coming in for me most afternoons for past week. Better than usual last two days, so presumably atmospherics.
It nice to see Quest and Dave again until them nasty RTE men mess it up again:p

Satdog

Gerry Wicklow wrote: »

Presely 42 and 45 have been coming in for me most afternoons for past week. Better than usual last two days, so presumably atmospherics.
It nice to see Quest and Dave again until them nasty RTE men mess it up again:p

Tried to retune 42 and 45 last night but only got a week PQ (pixelation)from Mt Leinster. Still happily watching Ch39 with no break-up.

marclt

I'm not sure but I think Ch.49 from Preseli may have been switched to it's full power allocation.

I've noticed that the signal strength and quality is the same as the other COM muxes.

Anyone else seeing the same?

M

Gerry Wicklow

All 3 Com muxes from Preseli have been booming in lately. I also got some from West Country so it may well be oddball weather sadly.

Gerry Wicklow

Gerry Wicklow wrote: »

All 3 Com muxes from Preseli have been booming in lately. I also got some from West Country so it may well be oddball weather sadly.

Wherever it is that you are located,you seem to have weaker mt leinster than most of us.
I've only received presely ch42 when presely has been strong.
No ch45 and definitely no ch49.

Also you might want to check if you have an auto tuning tv as llandonna has been a recent regular visitor and on an auto tuning tv [if that feature is on by default like most sony's] you may be picking up llandonna's com muxes.
Mind you -you'd notice this as your tuned BBC mux would be unavailable due to the interference and you'd have the llandonna one.

Satdog

No Chs 42, 45 & 49 Preseli for me either. Mt Leinster on Ch49 is blockly - signal strength good but PQ poor - obviously CCI.

ch 42 presely is working fine here tonight as presely ahead of an approaching weather front[when one of them approaches from the south or southeast,it really lifts presely] is very very strong.
I should imagine presely is making it's way up to Dublin and beyond tonight for anyone without an obvious obstruction to it's path.

llandonna is blasting in on ch60 aswell.

How come the signal is a lot lower on ch 57 though? I'd have thought the higher the channel on the group B,the worse the pick up.

Presely is way too strong for the very strong llandonna to cause a problem so far on ch 43 and 46.

I understand a constituent has informed Liz McManus T.D about the triplicate rebroadcasting of RTE at Mount Leinster.
She is putting down a Dáil question asking the green minister for Energy and communications what the purpose of this is and how much electricity has been used 24:7 on the project since last November at a time when theres no commercial broadcasts likely and at a time when RTE are losing money hand over fist.

I presume this is the only tx with 4 muxes instead of one contantly broadcasting at the moment?
Theres only one reason for it 8 months in now 24:7 and thats jamming.

The Dáil question should be interesting.

STB

Deleted User wrote: »

I understand a constituent has informed Liz McManus T.D about the triplicate rebroadcasting of RTE at Mount Leinster.
She is putting down a Dáil question asking the green minister for Energy and communications what the purpose of this is and how much electricity has been used 24:7 on the project since last November at a time when theres no commercial broadcasts likely and at a time when RTE are losing money hand over fist.

I presume this is the only tx with 4 muxes instead of one contantly broadcasting at the moment?
Theres only one reason for it 8 months in now 24:7 and thats jamming.

The Dáil question should be interesting.

Jamming ? Jamming who ?

Jamming as in the deliberate use of noise or signals in an attempt to disrupt communications ?

Arent these licensed frequencies that RTENL are test broadcasting on ?

Eamon Ryan surely doesnt run the transmission end of RTE. Day to day operational matters etc would be outside political interference would they not.

SRB

Hummmm.....

They'll probably reply they are running the Muxes to do a full study into the impact of the Welsh DTT Transmitters on the Irish DTT service. Wouldn't want to the Irish System wiped out by DTT from across the water in certain weather conditions, so need to leave it running to "get the full picture". Ministers will be horrifed that the Welsh DTT could be a problem and impact on the roll out of services in Ireland and will thank them for their deligence on the project.

STB

STB wrote: »

Jamming ? Jamming who ?

Jamming as in the deliberate use of noise or signals in an attempt to disrupt communications ?

Arent these licensed frequencies that RTENL are test broadcasting on ?

Indeed...they should fire up Athlone and Tullamore again at say 500kw each...with probably more listeners than 9 months of the deliberate jamming down at mt leinster...if as it seems the point is to for no good reason just broadcast on allocated frequencies for the crack like.

Eamon Ryan surely doesnt run the transmission end of RTE. Day to day operational matters etc would be outside political interference would they not.

The minister can impose a licence fee decrease however unlikely but certainly can demand due diligence in how it's spent to the point of freezing it.

srb wrote:

They'll probably reply they are running the Muxes to do a full study into the impact of the Welsh DTT Transmitters on the Irish DTT service. Wouldn't want to the Irish System wiped out by DTT from across the water in certain weather conditions, so need to leave it running to "get the full picture". Ministers will be horrifed that the Welsh DTT could be a problem and impact on the roll out of services in Ireland and will thank them for their deligence on the project.

They can't do it ad infinitum at a time when RTE has no money and there are no services on the way.
The impact of welsh services on their broadcasts on presely channels in wexford and wicklow is simple.Nothing receivable from mt leinster on the 3 spare muxes for 10's of 1000's of homes with aerials pointed to wales.
Only ch39 works.
You don't need 9 months of electricity bills and counting to work that one out.
For anyone else,probably similar coverage across all four muxes in the mt leinster service area.
I'm not an engineer but I'd have figured that out after a month...actually a few days.

As for the need for infill relays,one mux from mt leinster would be suffecient to work that out...It's a service area no different to any other part of the country.

STB

BB

Power usage:

DTT transmitters themselves are likely to be anything between 1 and 3kw.

CC Inteference with Wales:

The BBC etc do not have any remit to broadcast In ROI. Neither do RTE have any remit to broadacast into UK outside of government agreements.

Overflow reception from Wales may be inevitable but it is important not to become dependant on it. More importantly it is not a given right IMO. RTE are the national broadcaster for this country and the frequencies have been allocated to broadcast as such. If you want solid free reception of the UK stations you could buy a sat receiver and sat dish like the majority of peeps in ROI. Having said that, it is likely that Mt Leinsters's muxes will reduce to one when the service launches.

Using words like jamming is a little daft though. They are licensed to broadcast on the frequencies. That it intefers with your enjoyment of overflow reception of UK terrestrial freeview is unfortunate. I dont have that luxury myself so I suppose its a case of I will never miss it. I'll have to put up with the combo of sat and dtt.

Fact is,they don't have to broadcast on the frequencies they are using at the moment.
9 months testing on 3 extra muxes only in the south east can only have 1 motive and thats jamming.

Power is way more than 1 to 3 kw.I'd say 20 to 25kw going on field strengths here and yes with a professional meter.

What an utter carry on.

watty

Take tinfoil hat off head and fit as a larger reflector

Seriously though, have you tried a Yagi with a large piece of chicken wire on the rear reflector or rear reflector replaced by an MMDS dish?

I'd bet a 3.7m c-band mesh dish with a set-top yagi instead of horn would pickup Wales without the dreaded Mt. Leinster.

Also "Repeater" installtions etc. I found that a second screen earthed at one end only minimises Coax pickup. Also do a 3 turn loop about 10cm diameter as an RF choke on Coax downlead near receiver.

You could be right. Or it could be a test for Wales to see long term effect of Co-Channel interference vs weather across the Irish sea.

Longford Analogue when it started interfered with Divis Rebroadcast reception of Scotland (same channel). We can only guess at what the real motives and purposes of Engineering transmissions.

It's time it stopped.
You and I are paying for it to at best satisfy the curiosity of a few RTENL engineers if thats the reason for the test.
I suspect that jamming is the real reason.


They might as well be pointing the tx to the moon and applying for a research grant to test reception in weightless conditions :rolleyes:

STB

Deleted User wrote: »

Power is way more than 1 to 3 kw.I'd say 20 to 25kw going on field strengths here and yes with a professional meter.

What an utter carry on.

The ERP may be but the tx's arent.

watty

Actually about 20W of feed power at 144MHz was bounced off moon from Arecibo telescope. Ordinary SSB voice and Morse was received in UK with 13 element yagi and portable radio hand pointed at moon.

So if you used 10KW on Arecibo pointed at moon you could receive on "rubber duck"/Headphone cable type aerials on Band II FM!

I boggle at what gain the Radio Telescope must have.

mrdtv2010

Deleted User wrote: »

It's time it stopped.
You and I are paying for it to at best satisfy the curiosity of a few RTENL engineers if thats the reason for the test.
I suspect that jamming is the real reason.


They might as well be pointing the tx to the moon and applying for a research grant to test reception in weightless conditions :rolleyes:

I do find it extraordinary that this bleeding of red ink on balance sheets continues because:

a) its crystal clear, as it was years ago, that Irish commercial DTT is DOA.

b) the BCI could have learnt from the UK experience with DTT eight years ago. To paraphrase Bill Clinton: 'Its the economy stupid, it has to be free'.

c) The fannying about with different technical standards from the UK in the past twelve years has cost Ireland dear: they could have had a DTT service in 2000. Now the UK is changing standards; you can get a Sony Freeview 32 inch HD DVB-T2 TV from Tesco for £549 this month, as advertised in the UK Times on Saturday. Its all about economics. And today its all about Tesco economics.

d) The addressable Irish DTT market has shrunk to 200,000 homes MAX.

e) Sky have capitalised beautifully on their satellite RTE distribution monopoly.

f) Freesat is the perfect multichannel free digital system outside UPC areas.

g) The extended Mount Leinster tests on multiple channels are a King Canute like response to the overspill tide: they are incurring operating costs on a system which will now never be built in Ireland. It is time to pull the plug on this waste of RTE licence fee payers money.

h) RTE is very poorly positioned now to offer even a basic FTA DTT offer. Who is going to underwrite software development, marketing costs, staffing costs. operating costs and maintenance costs? The market is FAR FAR TOO SMALL for a standalone offer which derisks the platform. That is why RTE don't do anything.

Prediction: More talk and more inaction. Comme d'habitude...

CORRECTION on Freeview HD prices: Sony 32 inch KDL32EX403HD, Freeview HD, £499. With trade in of old TV is now £399. Page 18, full page add in Saturday's UK Times.

Sponge Bob

mrdtv2010 wrote: »

.Its all about economics. And today its all about Tesco economics.

CORRECTION on Freeview HD prices: Sony 32 inch KDL32EX403HD, Freeview HD, £499. With trade in of old TV is now £399. Page 18, full page add in Saturday's UK Times.

Or buy online

http://direct.tesco.com/product/default.aspx?R=208-1669

I can confirm Tesco are aware that the firmware in any 'cheap' Freeview HD box should be compatible with Saorview. Watch out for them around the £99/€99 mark at christmas.

STB

mrdtv2010 wrote: »

c) The fannying about with different technical standards from the UK in the past twelve years has cost Ireland dear: they could have had a DTT service in 2000. Now the UK is changing standards; you can get a Sony Freeview 32 inch HD DVB-T2 TV from Tesco for £549 this month, as advertised in the UK Times on Saturday. Its all about economics. And today its all about Tesco economics.

The UK have and do continue to fanny about with DVB-T standards. MPEG4 on DVB-T2 for a handful of HD stations and MPEG2 on DVB-T for all the SD stations in parallel for the forseeable future! Such confusion for the poor UK consumer!

However that has little or no interest to little old Ireland as we have adopted the standard that the rest of Europe have in Mpeg4 on DVB-T.

mrdtv2010 wrote: »

h) RTE is very poorly positioned now to offer even a basic FTA DTT offer. Who is going to underwrite software development, marketing costs, staffing costs. operating costs and maintenance costs? The market is FAR FAR TOO SMALL for a standalone offer which derisks the platform. That is why RTE don't do anything.

DTT is a given. The majority of the infrastructure is in place.

ASO is also a given.

Oh if only RTE had the licence fee income that the BBC collect from its 20 times population.

We Paddys, we can never seem to get it right, Can We.

Tír gan T2, tír gan anam

EDIT: By the way the LG 32 LF7700 will do the same for Irish DVB-T standards and has a Freesat HD tuner too for £350 (more importantly its actually reported as working here).

mrdtv2010

mrdtv2010 wrote: »

CORRECTION on Freeview HD prices: Sony 32 inch KDL32EX403HD, Freeview HD, £499. With trade in of old TV is now £399. Page 18, full page add in Saturday's UK Times.

Which retailer is doing that?
I need a new kitchen tv to replace the old 33" crt.

T'will be interesting to see if it handles mpeg 4 RTENL but I'm not worried as the house is piped with sky at any rate and obviously we have analogue untill 2012 at least and we will have the UK channels off the aerial.

The presely dtt is brilliant for the bed and breakfast guest rooms.
Thats what I use it mainly for.
Small wall hanging flat panel 22" tv's in each of the rooms with digital BBC1,2,3,4,ITV1,2,Ch4,5,More4 and BBC news aswell as RTE1 and 2,TG4 and from the fall TV3 aswell.

Thats 15 channels in perfect digital quality off an aerial with no dish and for free.

Who in this area would be mad enough to pay for those channels?

Of course it will be nice to get the commercial channels back aswell like film four,Dave,Fiver,Five USA [a great channel!] and E4.
I mean how long is a test a test?

mrdtv2010

Deleted User wrote: »

Which retailer is doing that?
I need a new kitchen tv to replace the old 33" crt.

T'will be interesting to see if it handles mpeg 4 RTENL but I'm not worried as the house is piped with sky at any rate and obviously we have analogue untill 2012 at least and we will have the UK channels off the aerial.

The presely dtt is brilliant for the bed and breakfast guest rooms.
Thats what I use it mainly for.
Small wall hanging flat panel 22" tv's in each of the rooms with digital BBC1,2,3,4,ITV1,2,Ch4,5,More4 and BBC news aswell as RTE1 and 2,TG4 and from the fall TV3 aswell.

Thats 15 channels in perfect digital quality off an aerial with no dish and for free.

Who in this area would be mad enough to pay for those channels?

Of course it will be nice to get the commercial channels back aswell like film four,Dave,Fiver,Five USA [a great channel!] and E4.
I mean how long is a test a test?

www.tesco.com, somebody quoted a link on the board in this thread.

The main problem I think is that RTE management and RTENL are very jealous of the success of the UK Freeview system. Its very interesting if you read the UK forums how quickly Freeview HD is being taken up across the UK and, of course, the prices are falling like a stone. It would be far better for them to fess up, launch a one MUX ROI service, and cash in on the coming economics from Freeview HD boxes & Tvs in the UK. That would be a case of realpolitik in the recession but the tragic history in Ireland has been television standards partition!! To absolutely no avail as we survey the trainwreck which is Irish DTT.

BB: for your convenience, here is the link:

http://direct.tesco.com/product/default.aspx?R=208-1669

watty

Also if you NEED a dish, i.e. not near coast or boarder you can feed up to 1024 TVs from one dish and a Quattro LNB. In fact if the Sat Tuners have DISEQC you can have 4x Quattro LNBs 13E, 19E, Freesat 28.2 on one dish and anything on 2nd dish. The cost excluding cables, Quattros and Dish is about 30 Eur per Tuner for a large trunk AMP + multiswitch system for 4 satellites.

icdg

Spongebob, play the ball and not the man please. No more potentially libelous comments that might get boards.ie in trouble.

Mr McBoatface

I posted it in another thread earlier but it seem appropriate to mention it here too. I think Mount Leinster have turned off the extra muxes. I lost all channels on all muxes earlier today only to have them reappear about 20 minutes later on just one mux.

Can anybody else confirm that the extra muxes are now gone ?

bothyhead

jobyrne30 wrote: »

I posted it in another thread earlier but it seem appropriate to mention it here too. I think Mount Leinster have turned off the extra muxes. I lost all channels on all muxes earlier today only to have them reappear about 20 minutes later on just one mux.

Can anybody else confirm that the extra muxes are now gone ?

Yes, I can

I haven't had a chance to see exactly how many are gone, but I did a quick flick and some of the previously blocked channels are now coming in with a quality of 100%.

Happy days - let's hope it remains that way!

yes!!!!!!!!!!!
ch49 and ch 42 are blasting in and it's not a lift.

RTE are on 45 only and have switched off ch39 which is a bit stupid as they should be on 39 not 45 as co wexford and south wicklow will have no digital service.

Wonder how long this will last?

Sponge Bob

Deleted User wrote: »

Wonder how long this will last?

All week, Eamon Ryan is in Japan and is unavailable to deal with frequency co-ordination issues while he peddles the standard Smart Green waffle in Asia.

"9:40～10:10 Lecture "Ireland: Smart Economy, Green Innovation"

http://www.ict-summit.jp/2010/en/program/index.html


OMG , look who is listening :eek:

lol

marclt

Oh great!

Back to analogue for me!! :rolleyes:

marclt

marclt wrote: »

Oh great!

Back to analogue for me!! :rolleyes:

Same here for RTE...

bothyhead

I'm not sure if this is related, but I lost radio reception (RTE, Radio 1) today for about half an hour. This also happened with the last two weeks as well. Presumably our Radio reception is also coming from Mt Leinster. I wonder if they are re-configuring, or perhaps having transmitter problems. Could this be tied up with yesterday's switch-off of the TV muxes ...

Antenna

I did hear that Radio 1 from Mt leinster had a long outage last Thursday for a time during the afternoon, but other radio channels (from there) were OK.

This situation would have nothing to do with DTT.

PyeContinental

It seems to be only using channel 45 now.
This is no good though, it needs to be channel 39. :mad:

I'm guessing and this is only a guess that they are taking down the extra mux tx equipment in preparation for using it for some of the many infill relays.

I shall have the ear of one of the engineers in the next week in the flesh which could be a very interesting chat!

RTENL will have to be told that ch39 is the only practical solution to the widespread usage of presely.
I can get ch45 here no bother if I unplug presely but I won't be doing that.

If they don't do something on that front aswell,RTE in this household and TV3 will be restricted to one tv at a time via sky.
Another solution would be to separately wire a mt leinster aerial to a decoder and pipe this receiver without rf pass through to other tv's.
I'm not sure how you would do that and it would be just simpler if RTENL switched to 39.

Sponge Bob

Deleted User wrote: »

I'm guessing and this is only a guess that they are taking down the extra mux tx equipment in preparation for using it for some of the many infill relays.

Would the TX gear not be a tad Massive for a relay

I shall have the ear of one of the engineers in the next week in the flesh which could be a very interesting chat!

Do tell us how it goes, I shall await agog!

Macy0161

It'll be interesting to see how this plays out, as Preseli would be my natural option for freeview. Pre-aso I was getting weak Preseli ITV through the back of a wideband grid, in the loft, pointing at Kippure!

What channel are the HD channels on/ down for, channel 50?

If most of Preseli channels are free from interference from Mount Leinster, are channels 50 and 54 too close to use a combiner?