Greystones DTT services off the air?

liamf

Hi,

some time ago I got DTT working using MythTV, Hauppauge HDR4000 card, Ubuntu 9.10, and much driver trouble.

This was pointing at Greystones DTT transmitter, loft UHF antenna.

Then I promptly forgot all about it.

So now, when I go back to this, I get signal lock from the transmitter but not services at all.

Can anyone else confirm that the services are not on-air currently from the greystones transmitter? Or has something in the (somewhat delicate) MythTV setup got broke?

Thanks
Liam

rurs

Just did a scan on ch.52, all services available.
Maybe RTENL have changed IDs or something, and you'll need to rescan?

liamf

Ah.

Well that would explain it.

When I had it working previously, it was on 738MHz which I think is channel53 or 54 ... that must have been a test transmission.

I will rescan this evening.

Thanks
Liam

fat-tony

738MHz is channel 54, which is Three Rock. Greystones is 722MHz - channel 52 as stated by other poster. This hasn't changed in the last two years.

liamf

Curiouser and curiouser.

Because I use a directional UHF C/D antenna which I am sure is pointed at the Greystones transmitter (I can practically see the Greystones transmitter from my house).

And it was saying 738Mhz back in the day. Channels perfectly clear too.

I will do some scanning later.

So it is safe to assume that the Greystones transmitter is never off the air these days?

rurs

My grid aerial is aligned for 3 Rock, so it's getting Greystones from behind, (with occasional break up)... plus it's the wrong polarization, but it seems the DTT signals are very forgiving...I don't have line of sight to either.

Maybe the fact that it's in the attic is affecting reception from Greystones? It is only a relay, I believe, much lower power than 3 Rock. Are you sure you have it vertically polarized?

I don't check Greystones that often, so I can't tell you if it's constant, I did do a full scan today, got ch. 47 (Cairn Hill from Longford?) for the first time, the current high pressure weather might give you strange results if you scan tonight.

liamf

OK, I have conducted some experiments and based on the evidence I am forced to come to a startling conclusion;

Someone has gone and moved Three Rock when I wasn't looking.

Or, I suppose, that actually what I am receiving is a signal reflection off Bray Head or something.

But my money is on someone moving Three Rock and not telling us.

I only get reception now by pointing the directional antenna about mid way between Three Rock and Greystones from here.

I bet it was aliens.

fat-tony

liamf wrote: »

Curiouser and curiouser.

Because I use a directional UHF C/D antenna which I am sure is pointed at the Greystones transmitter (I can practically see the Greystones transmitter from my house).

And it was saying 738Mhz back in the day. Channels perfectly clear too.

I will do some scanning later.

So it is safe to assume that the Greystones transmitter is never off the air these days?

What was saying 738MHz? The tuner? Or were you looking at the info in the data stream? The NIT has a descriptor (0x62 Frequency List) which gives the frequency as 738000KHz and a descriptor (0x5A Terrestrial Delivery System) which has a value of the centre frequency of 198500KHz:rolleyes: I would assume this info is the same for all transmitters, but it may be that the Greystones relay is being fed from Three Rock and inherits the values? Maybe someone at another main transmitter - Mt. Leinster or Mullaghanish or whatever could check the values.

The Greystones relay has been very solid, no significant outages that I noticed.

liamf

What was saying 738MHz? The tuner? Or were you looking at the info in the data stream? The NIT has a descriptor (0x62 Frequency List) which gives the frequency as 738000KHz and a descriptor (0x5A Terrestrial Delivery System) which has a value of the centre frequency of 198500KHz:rolleyes:

The tuner was saying 738MHz.

Most amusing about the 198500KHz .. I was wondering where that was coming from ... if you scan using me-tv it will find all the services on 738. They promptly disappear off to 198500KHz and timeout looking for some more ...

I had not bothered to capture some stream and analyse it.

I still get 738Mhz, but not great quality to be honest, and it's being reflected off something so not necessarily reliable at the moment - the antenna is pointing in completely the wrong direction, at least 90 degrees from the "real" direcion of Three Rock.

I can't get 722 (Greystones) at all ... I had looked with mpeg4ireland and it looked like I should be able to get it ... but probably there are too many houses in the way for an indoor antenna.

It looks like what was happening before was I was pointing it in the greystones direction and (by accident) getting three rock from behind or something. I also :rolleyes: had not noticed that Three Rock and Greystones are different polarisations, so I was using horizontal all the time. But it doesn't work vertically either.

I may try to do some outdoor experiments later.

fat-tony

You're confusing me, liamf!
You say that you are using a group C/D aerial in the first and third posts. Now you are saying that you are using an indoor antenna. I take it that this is a set-top aerial and that you are not referring to your original aerial in the attic?
I have a basic wideband contract aerial in the attic and it picks up the Greystones relay analogue and DTT signals fine. For my PC tuner I just use a little home-made quarter wave dipole, but this is outside. I'm about 2km from the transmitter. Polarisation is vertical.
You may be getting 738Mhz signal from Kippure, which is a single frequency network with Three Rock. From my location Kippure is due west and Three Rock is slightly west of north. You may be picking up Kippure - I was getting it (poorly) from a roof aerial when it was on channel 61. I could also receive Three Rock from channel 54, but once Kippure moved to 54 I couldn't distinguish them.
I think your best bet is the Greystones relay. Just orientate your attic aerial for vertical polarisation and you should get the signal ok.

Your location details say that you're in Bray. This, I take it, is to throw us off the scent and you're actually in the metropolis of Greystones!

liamf

You're confusing me, liamf!

sorry 'bout that.

You say that you are using a group C/D aerial in the first and third posts. Now you are saying that you are using an indoor antenna. I take it that this is a set-top aerial and that you are not referring to your original aerial in the attic?

I'm using a C/D aerial ... I just have it mounted in the attic. The wiring is easier ... and it's easier to try than mounting it outside first.

And it used to work just fine, dammit

I tried Greystones with vertical orientation but didn't get anywhere ... this may well be because from my location (and *inside* the attic) I am essentially pointing it through a row of houses. While I might have better luck mounting it outside on the chimney, that, however, will require some kit which I don't have at the moment.

Kippure ... hmm ... an intriguing idea. I will try that too.

fat-tony

OK now it's my turn to eat humble pie. Greystones has gone off the air sometime since mid morning. All the more of a bummer as I have just moved my home-made antenna to a "better" location and have routed the cable through a drilled hole in the wall. When I couldn't get a signal on the PC, I assumed I'd bodged a connection somewhere, took everything down to check and couldn't find a problem. Then I turned on the main TV which is connected to a separate loft aerial and.... no signal. Well, feck it anyway:o:o:o


18:05 - just checked the signal - it's back. My antenna is pulling in the signal well in its new location.

liamf

OK, thanks.

With some judicious antenna positioning I got Three Rock to work (and pointing in the expected direction too, not getting a reflection off something).

Of course it took an hour of messing with MythTV settings to get it to playback smoothly.

Now if I could just get satellite HD to playback live in Myth, I'd be all done.
But that would be off topic.

For now I will leave it pointing at Three Rock.

Thanks
Liam

fat-tony

I'm surprised you got Three Rock working and not Greystones. Where are you located in relation to the centre of Greystones? Three Rock is difficult with an indoor aerial as it's sheltered by Bray Head and the Little Sugar Loaf. I can get it with an outdoor aerial by pointing at the gap between the two obstacles. Greystones relay is low powered, though and is really meant to service the town and environs, but I've heard reports of it being received near Wicklow town.

liamf

Location is more or less here:
http://pininthemap.com/pp86b0367af6b9b4b41

Greystones relay is almost due south of here, and should be visible (but I couldn't get anything at all from it: I expect this is because due south from inside the attic is pointing through 2 or 3 houses. It might work on the chimney)

Three Rock working OK at the moment. I await more challenging weather conditions with interest.

fat-tony

Greystones relay would be shielded from you by Bray Head/Little Sugar Loaf and it probably doesn't beam in your direction. You can see Kippure's aircraft beacon lights from the Southern Cross Road. It's due west - towards the Killarney Road. I reckon that's where you're getting CH 54 (738MHz) signal from. Three Rock is also visible, but Kippure bangs out a lot more power I think.