A Bit OT - Satellite & Terrestrial TV in West Cork, Ireland

[Adrian]

HI All

A tiny bit Off Topic - but if I can't get any joy out of the people I've paid to do this job then I may end up DIY-ing it myself !

There was a discussion a few months back about the practicalities of DIY setting up for a sky+ system out here in West Cork. General consensus seemed to be that it wasn't such a difficult task - but, in the end, time constraints cut in and I got a man in

Result is that we have a little (oval - perhaps 80cm ?) sat dish up on the gable end - with a clear view of the sky....

This is mostly OK (signal stength on channel 1 is about 50%, quality about 25%, Stength on channel 2 is lower and quality doesn't even indicate on the scale) - with a little 'stuttering' and picture freezing from time to time.

When we have a heavy downpour the signal disappears altogether - which means that the sky+ box gives up on any recordings that we're trying to do.

Should we expect this situation (about the signal strength) - we're out in the West of County Cork, near a little place called Ballydehob.

The same 'expert installers' ( it says so on their van !) fitted an aerial for Terrestrial Irish TV. We are about 5 miles direct line of sight from the transmitter at Mount Gabriel - and getting a noticeably snowy picture with some ghosting. The aerial is a 4 dipole + reflector arrangement, that they've fitted in the loft (where it has to look through two concrete walls and is about 1ft from an enormous steel 'I-beam' which forms the ridge of the house. To compensate for this, they've added a high-gain amplifier....

To be fair - they did say that if we weren't happy then they'd come back & fit the aerial outside...

So - what should I expect in terms of satellite 'reliability' and terrestrial picture quality?? - given that we are somewhat 'out in the sticks - I don't want to be unreasonable with them, but I also don;'t want to pay good euro for a 2nd-class job...

Advice appreciated - thanks in advance

Adrian

[Brian Sharrock]

SKY , who now seem to broadcast to Irish consumers - judging from the 'Ireland' options when one 'presses the red button' - would be the definitive expert on what signal strength they aniticipate at that Lat Long. {They will have a map of the satellite's broadcast 'footprint'}. however a more practical approach may be to wander around your neighbourhood looking out for 'dishes' on the south-east facades of houses and ask them what their experience is. :) Neighbours with dishes may say ' Our symptoms are precisely as yours! ' OR 'No, we get a perfect picture!' Either way you'll get a rapid response and then now how to proceed.

AIUI, Channel 1 and 2 (off the quad LNB) are irrelevant as you may be watching say Sky-One on Channel 1 or 2 so the signal strength should be the same! Channel 1 AUI is the defaul and feeds the recorder while Channel 2 becomes the alternate. You may have a dodgy Sky+ box and Channel 2's chain is duff (to use a technical term). In UK Sky has a phone-line which will offer advise.

A TV aerial, properly called a Yagi Array, only has one proper dipole (sometimes folded) this dipole is in fornt of the reflector and is where the signal is received. The other elements are properly called 'directors' and contribute to received power by both adding to the signal [Gain] AND making the beam more narrow [Beam width] - requiring 'better' pointing. Four dipoles plus reflector - three directors(?) doesn't seem at first glance to be very directional - glancing out of my window at neighbouring yagi arrays I count seven directors poiting at a transmitter in visual range on top of a hill perhaps six miles away. Three directors might indicate a low gain wide beamwidth array.

A high gain amplifier will increase the noise just as much as the signal and may swamp the input stages of your receivers. It's the wrong way round _ I'd say an oirish way - but that's probably banned by some legislation or other ; so I won't_. :) You need to have a good signal off the dipole.

It's _may_ not be the inide/outside aspectthat's wrong but the GAIN/BEAMWIDTH that's incorrectly supplied. BTW, with direct line-of-sight there's perhaps multiple paths for the signal to reach you You haven't mentioned the juxtapositioning of the 'enormous' steel to the yagi; nor the orientation of the steel to the transmitter (aligned/broadside on/ skewed. Perhaps the signal is bouncing off and your device is 'receiving' a back-lobe?

There are _no_ 'good euro' .... :)

[Andy Hall]

Basically the dish isn't large enough. Signal strength needs to be higher, but more importantly the signal quality.

It may be possible to make *some* improvement with a better quality LNB on the dish but this is usually a second order thing.

This is pointless. Adding an amplifier when the signal is poor adds noise as well and doesn;t improve multipath reception.

I think you should ask them to do that, to be sure.

It should have gone outside in the first place,

[tony sayer]

In article , Adrian writes

Bigger dish required!. See also

and

a post to alt.satellite.tv.europe

Kick them out and try to find someone who knows that their doing or DIY that is a total crap way of going about TV reception!..

Yes what they should have done in the first place. If it were me I'd be demanding my money back at this point!. Unless you told them to put it there against their advice..

And a post to uk.tech.digital-tv

might turn up someone recommendable in your area but good aerial riggers are like finding virgins in Cardiff.)

[Christian McArdle]

You need a bigger dish, probably round, not the little ovals you can use in SE England.

Ditch the amplifier. Waste of time. Amplifiers compensate for long downleads or splitting. They are no good for rescuing below par aerial installations.

You have ghosting. There could be two causes of this. Firstly, your noisy loft installation. Secondly, being close to a high power transmitter. I can't say which problem you have.

The first will be fixed by installing outside. The second would be fixed by using a log periodic aerial instead of a Yagi. Log periodics have lowish gain (but do you care?) but, more importantly, are very good at eliminating reflections without all the spurious peaks you get on a Yagi response chart. You basically point at the transmitter and get a good signal.

If you have a really stubborn fixed reflection, such as off a large building or mountain, you might need something more exotic, such as a Yagi phased array, although these can be very problematic to set up (particularly wideband) and are very sensitive to slippage from being blown around.

Christian.

[Adrian]

Hi Brian

Thanks for the reply...

Don't have many neighbours out here - but I have asked a few locals and they seem to be able to get acceptable reception.

It did seem a bit strange to me. Maybe I'll swap the plugs from the wall to the sky-box and see if the fault moves (nail through a cable, anybody ? )

Might also take a look in the loft and see what sort of cable the electrician installed - wonder if it's proper satellite stuff ?

I've a sneaking suspicion that the joins between the existing 'house' cabling and the new dish were of the 'insulation tape & three Hail Marys' variety - could be something odd going on there..?

Nope - I guess this is a form of 'curtain' array - four little 'bow-tie' elements sitting in front of a mesh reflector.

All 'fitted' in the loft by the expedient of nailing the reflector to a roof-joist (!) - although the installer did use a signal-strength meter to set it up....

I thought as much - but thanks for confirming that I'm on the right track...

The house is pretty much 'gable on' to the transmitter - so the aerial is looking through the end gable wall, a small internal wall, and 'along' the line of the big metal beam. Plenty of room for relections / multiple signal paths there !

There are when they are buying petrol at 2/3 the UK price over here !

Many thanks - I'll go investigate

Regards Adrian

[Adrian]

My thoughts entirely

Why would they fit a 'too small' dish ? Seems to be asking for trouble

Thanks - you're confirming my suspicions - wanted to be sure before tackilng them...

To be sure

I guess the only thing in their defence was that it was pouring down at the time - but, working in the Emerald Isle you tend to expect that!

Thanks again Adrian

[Adrian]

Thanks.... Does a 'too small' dish explain why there's the difference in signal strength between the two channels ?

Thought as much....

Nope - didn't advise them either way..... - after all - it says 'expert' on their van

Can't say I've ever tried that

Thanks again Adrian

[Adrian]

So I was told before we moved out here - but I thought the 'experts' would know what they were doing ?

Thanks - you're confirming my own suspicions

Not sure how much power the transmitter is putting out - about 2kw according to Wolfbane

The existing aerial's a sort of '4 dipoles and a single mesh reflector' arrangement - not a Yagi

Wouldn't think we'll need that....

Thanks - I'll call them back in Adrian

[Brian Sharrock]

The SKY+ box has two channels internally but are both fed off the one aerial. This aerial is actually a reflecting dish focussing the teeny-weeny signals off the satellite onto a Quad LNB - the cables -from the SKY+ box are sending a DC signal to the LNB's which sets up each exercised LNB solid -state device to 'tune-into' the desired frequency and orientation of the satellite's many signals. Get a decent signal on Chanell 1, swap over the cables; the signal strength should be exactly the same - it it isn't then you've got a faulty SKY+ box; if they change then you've got a faulty Quad LNB. {Or faulty cables/connectors }

So, if they can get it - so should you ! Complain to SKY!

I haven't been able to sight "Ballydehob " on Google Earth's site! 'Ballydehob' isn't the Gaelic for "valley of no signal" is it? So I don't know where abouts you are in relationship to Mount Gabriel - {Truthfully; I don't now where that is either! Do you ever get trumpet blasts?}

An Irish outfit that claims some expertise in terrestial Television - it probalby says so on their vans :- recommends:-

NEW UHF TRANSMITTER ON AIR AT MOUNT GABRIEL, CO CORK

RTE 1 NETWORK 2 TG4 Channel 29 Channel 33 Channel 23

For best reception for viewers, a UHF Group A or broadband aerial should be used.

For the east and south, aerials should be horizontally polarised.

For the north and west, aerials should be vertically polarised.

[Andy Hall]

Perhaps this is what the distributor had in stock and told them it was OK.

You would. Also, as you've discovered, satellite signal strength drops when it's raining.

However, it's really the error rate that counts.

The other thing to do before they come back is to take a look at this site

the satellite bands used by Sky, (and many others), there are two bands (high and low) and vertically and horizontally polarised signals. When you select the program you want to watch on the receiver, it sends appropriate control signals up the cable to the LNB at the dish to select which of the 4 permutations should be used - it as actually the LNB that does the band and polarisation selection.

What I would recommend is to choose a program at the bottom, middle and top of each band and of each polarisation (i.e. 12 programs altogether). Note them down with the Sky channel numbers. Then when the installers come back, try them all out and make sure they are OK, ideally when it's raining. If all of this works reliably, then you can be reasonably confident that all channels will.

[Adrian]

Will do that check later on tonight..... (when the box is not 'in use')!

I did take a look in the loft, and the joints between the dish coax and the downlead in the walls are simply 'wrapped & insulating tape' - maybe there's a c*ck-up there ??

Kit was installed by an independant installer - Skybox still thinks it lives in the UK (long & complicated story)

We're pretty much due East of Gabriel. Ballydehob is to be found along the N71 from Skibbereen to Schull - about 1.5 hours drive west of Cork city...

That's the one !

Correct

That'd be us then

Thanks Adrian

[Adrian]

Ooh you cynic !

Yes - understood

Agreed - that'd be the 'quality' reading on the setup screen ?

Fairy nuff - will do some homework - thanks !

Adrian

[ephraim_pule]

Adrain, Some local practicalities, I suggest that you go to Skib, over the bridge past the hotel, turn left and on the left-hand-side about 50 metres on is a v small TV shop. Not very impressive but they are SKY agents, they service trawler radios, are radio enthusiasts and really understand both the basics of satellite and terrestrial.

There are two sons of the fierce older lady, one does TV stuff and the other real radio.

I addition, they understand the special problems of the area, bounce off Gabriel, just how low the satellites are, etc. They have sorted my sat-TV a couple of times after the gales displaced dishes. I have discussed the physics of it all and I am certain that they know their stuff.

Bite the bullet, spend a few Euros and get the local experts. Oh, I think the bigger firm "T" in the centre of Skib much more "impressive" but may not be as good, lots of lads and flash.

I'll be in Ballydehob next week and when I remember the name of the excellent Skib TV folks, I'll put them on this discussion. I really do think that local experts (I do mean experts) will be a better bet than abstract advice from folks who have not had to set up aerials in W Cork. (9deg West).

EP

PS... Although from the furthest West in Europe and a tad remote, the folks I have recommended were trained in good Technical Colleges and go to all the update events in London etc. Have alook at the quality and orice of their HD stuff in their quaint little shop

[Andy Hall]

Ah.... They've used cable that was in the wall?

There is a pretty good chance that this is TV coax. This cable is basically s**te and is marginal for UHF TV which has a frequency range up to about 900MHz. The frequencies used between LNBs and receivers go to around twice that and the effect will be signal loss and possibly cable reflections etc.

The LNB cable should be CT100 and it should be home run all the way to the receiver.

[Andy Hall]

Wouldn't be the first time. Surely you've been to a plumbers merchants when the local trade are in there for the morning mothers meeting. I wouldn't expect a big difference.....

Exactly.

I hadn't spotted that you had a Sky+ box. That doesn't really make a difference to the above. Effectively there are two or possibly 4 independent LNBs in one at the dish.

[Adrian]

Yup !

The electrician (bless him) did go to the trouble of installing a double aerial socket and a single side-by-side - so he was (maybe ?) thinking 'Sky+ and terrestrial'. I looked at the 'built-in' cable last night and couldn't see any info printed on it - it's got braid and foil screening, and is semi-airspaced (the white plastic 'honeycombe' effect) - but I couldn't see any maker's mark....

Hmmm !

I did double-check the signa; strengths etc on the skybox - last night both 'meters' were showing 50% strength, input 1 showed about 40% quality and 2 showed about 30%. Swapping the leads at the wall plate made not difference, also swapping the leads at the bcak of the skybox had no effect.... dunno what that proves ??

That'd be ideal, I agree...

Must try to get up there and measure the size of the dish.... that might prove something.....?

Thanks Adrian

[Adrian]

I've not seen that one...... This isn't the one just up the road from Fields, with the big ham radio beam on the top, is it ??

Excellent - that's what i need..... can even talk some ham radio with them to break the ice !

Many thanks

Those are the 'experts' who put this installation in - losing faith with them (just a bit !)

Yes - please do...

For the time being, confirmation of their whereabouts will do fine - we'll be in Skib later this week

Agreed - though every input is welcome.... Where is your installation, do you have problems with loss of signal during heavy rain - is this a symptom of my poor installation or is it to be expected out here ..?

Will do - many thanks ! Adrian

[Christian McArdle]

Can you identify it? 95% of all TV aerials are Yagis. (And 95% of statistics are made up on the spot).

Christian.

[Christian McArdle]

There are other cables that would be acceptable for this installation, like H109 or RG6 (provided it is indoors).

Christian.