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

[Brian Sharrock]

Chipping in, again, I can't quite parse what you're saying; is the aerial array; -

Case A:

-- -- -- -- < four off dipoles

--------------------------- < mesh reflector

or;-

Case B: -- -- -- < four 'dipoles' = one dipole and three directors(?) --

------------- < mesh reflector

In both Case A and Case B the transmitter is normal and on the 'dipole' side of the mesh. BTW, the 'mesh' (reflector) is theoretically infinitely large and stops all signals from behind ... luckily for us, the Lord ensured that the reflectors could be attacked with tin-snips and didn't need infinite dimensions; turns out that one only _needs_ the reflector to be this* big and the mesh only has to be this* far behind the dipoles

[*this is a function of frequency]

Case B would be normal and what RTE intend when they call for a UHF Band A aerial; CASE A is highly unusual - what RF Engineers describes as a phased array with 'intriguing' possibilities of gain, bandwidth and beamwidth as a function of frequency!

[Andy Hall]

If there's foil it might be CT 100 but no guarantee.

I would arrange for the whole thing to be done in known CT100 all the way then you know what you have.

That they are equal.

Probably that it;s too small.

You would need to ask a known good local installer, but I would expect that a 90-100cm round dish with good LNB and CT100 cables all the way to the receiver would be the expectation.

[ephraim_pule]

Adrian May I add that the people that I recommend also found it difficult to understand the losses between my dish and set. So they slung a good length of new "satelite" cable from the roof straight from the dish and in thru' the sitting-room window to by-pass the installed older co-ax.

Lo and behold, v good signal/reception. So up into the roof space where the old cable ran. Mixtures of old coax with copper braid and better "satellite" cable with foil, jointed by twisting inners to inners and outers to outers with lots of insulating tape!

Whole lot sorted and signal OK despite rain and locality.

I understand that "T" did the job before but if they argue I'll withdraw, without reserve, after all folks in IE are v litigious :-)

I am not impressed with posh vans with logos claiming excellence painted on the outside. Much better to work with an honest bloke who arrives in a beat-up old estate but knows the physics, 'cos he's an real specialist, trained but also a personal enthusiast. Have a look at the TVs in their shop, the serious folk deal with them despite it looking a tiny outfit.

Adrian, this is getting to be something of a minority interest. If you want further chat, I suggest you send me a note to the address I gave you earlier this year when you announced your move to W Cork.

For those who are finding this boring, I think there's a more general issue, it's really about a plea to use good, well-trained, honest folks who need a fair day's pay rather that the big Co. with lots of adverts who employ lads who can just about do a SKY instal on a S facing house and not much more.

I think this applies to quite a lot of DIY... honest folks, trained, competent and keen, earning a fair return and sod the cowboys. EP

EP

[Adrian]

Yes - that's the one !

No - no directors, just cunningly-phased dipoles and a mesh reflector. Low-gain, wide-angle - methinks

Even better if the mesh is electrically connected to the gurt big I-beam (by virtue of being physically in contact with it !

Had a quick discussion with the installers today and suggested that I might be interested in paying their bill if they might be interested in coming back and doing a proper installation...

..we'll see....

Thanks Adrian

[Brian Sharrock]

snip

Let that be a lesson to me; I assumed that it must be a Yagi. After all, that's what _everybody_ uses. I re-read your ' ... not a Yagi' and thought; - "No! they couldn't use that type ... could they?"

The groundng effect of a lump of steel shouldn't hurt it too much. 'Theoreticaaly' the reflector is the minimum area that one can 'get away with' . Additional material, provided it's behind the dipoles, shouldn't matter.

RF energy is what 'we' call 'funny stuff' (another technical term ) bits of cable, such as co-ax, that seem to be normally resitsive become 'open circuit' and/or 'dead short circuit' at different points along the cable once one starts trying to stuff rf energy along it: technically it's all to do with lambda and halve and quarters but as lambda changes with frequency it all get too hard for humnas to suss out. { partly becaue it's all tto hard to imagine 'receiving' things off an aerial - we utilise the theory of reciprocity and pretend that the aerial is a transmitter } Your Irish installers seem to have attempted to install a phased array, wherein one dipole will 'interfere' with it's adjacent neighbour cauisng nulls and maxima to overlap creating a narrowing of the beam without significantly increasing the received signal . Adding these four signals together in such a manner that they sum accumulatively and not destructively is a non-trivial task. Attempting to transmit such a signal down a non-homogenous cable to a receiver is another minefield. Reflections at junctions and terminations at cable end will almost invariabley caue a 'Standing Wave' to be generated, and Sod's Law [may be known as Murphy's Law in the Republic] will almost guarantee that you may have an minima at the end.

Now to find out if there's any 'good euro' :)

[Christian McArdle]

There's no need to switch to email if the subject is still on topic and doesn't involve personal details. If people are bored, they can ignore the thread.

Christian.

[tony sayer]

Not that simple, depends on what directional characteristics you want..

Thats because its a bit difficult to understand, theres nothing "funny" about it!...

Good idea;)

I thought he was a Yank?..

[jg.campbell.ng]

[...]

[...]

[...]

Maybe this has been clarified earlier in the thread ...

It seems likely to me that the OP's aerial is a 'stacked dipole array' as shown in Fi.g 5 of:

They used to be marketed under the product name 'Colour King' (I've forgotten the maker). I have seen them on relatively new houses here in the Donegal area --- which is hilly and has otherwise marginal reception from across the national border. But, as someone speculated, it could be that they are used because they happen to be surplus stock.

They used to be used a lot in Ireland for 'extremely long distance reception' (my term), e.g. receiving BBC, ITV in the Irish midlands --- order of 50-70 miles from the transmitter in the Mournes. You would see them atop gynormously high masts. Incidentally, compared to what went before (huge Yagi-like arrays --- Hirschmann brand --- that weighed a ton), they seemed to be machanically less fragile and offered less wind cross-section. After the stacked dipole array, the same areas switched to what appeared to be a single dipole design, with a dish shaped mesh reflector. Now, of course, everyone in those regions use satellite or cable.

(Regarding terrestial reception.) If the OP is in a flatish area, then find a neighbour with good reception and do as they do --- same aerial type, some band (colour coded?), same polarisation. It could be that you can experiment with aerial mounted on something easily reachable from the ground; five miles from the transmitter was mentioned, I think. If you are in a very undulating area, then all bets are off. As others have noted, skilled aerial installers may be hard to find; for that reason alone, you should be prepared to pay decently for a decent job done, and a job that will last. Installing an aerial on a chimney is easily d.i.y. But you may not have ladders and a head for heights.

Best regards,

Jon C.

[Dave Liquorice]

Not a useful URL that...

By the the "two channels" I take it you mean the two independant ouputs from the LNB. They should be pretty much the same. I suspect your professional cowboys haven't aligned the thing properly, did they use a signal meter of some sort to do the alignment?

the footprint for the various beams. IMHO a properly aligned Zone 1 (the smaller of the two) minidish should be fine, Zone 2 would be better.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Adrian saying something like:

Sorry for the delay, got here as fast as I could.

Right, the sat dish. Fuck the Sky dish, you need a min of 90cm and preferably a 1M dish. Sorted.

As far as the aerials go; if you're in an area where all the Irish channels are on UHF, then you need an outside antenna of the appropriate channel group.

If RTE1 and 2 are still on VHF in your area, you need a box section VHF antenna (it's 2 dipoles and a square reflector) and a UHF one for the other channels (TV3, TG4, C6) and you simply combine them into one at the masthead.

Easy.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Adrian saying something like:

Fuicking hell. You've encountered the Untrained Clowns Satellite Installation Company. They've got branches all over the place.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Adrian saying something like:

Not too much - the recommended dish for most of Ireland is around 80cm, but it's inadequate. Much, much better to simply get a 1M dish in the first place.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Liquorice" saying something like:

[Adrian]

Yes - a truly universal organisation. I queried the 'twist-it-together' approach with the shop manager on the phone - he didn't seem at all concerned - 'Ah no - that's how we always do it'......

Still waiting for them to come back for a sceond attempt..

I'll keep you all updated !

Adrian

[Adrian]

Which I think was the advice I was given when I first asked the question here a couple of months ago...

Can't decide an easy 'exit strategy' from these cowboys. Sorely tempted to dismantle their handywork and take it back to them in a big cardboard box ! Trouble is - the dish is up on the end gable, and it's a bit higher than I'm happy with, without using a roof ladder....

...but I'm tempted

'Spose I could ask the 'other expert' do do an install for me and to take their stuff down at the same time

Regards Adrian

[Adrian]

No problem !.

Might be a bit of a problem - it's up high & I'm not good on ladders... and it's raining

Oh - I see what you mean..... - sounds right....

I'm sure it's UHF - and the antenna they've supplied claims to be wideband - just needs to be outside, I think..

..When you know how..... !

Thanks for the advice Adrian

[Dave Liquorice]

So those coverage maps are crap are they? References for your assertion please.

[tony sayer]

In article , Grimly Curmudgeon writes

What's wrong with a simple multi element Yagi array For Band three then?...

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Liquorice" saying something like:

Personal experience - that do you?

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember tony sayer saying something like:

Not commonly available from what I've seen and is a bit unweildy. The boxy twin element [1] is fairly common and works well, but as Adrian is apparently served by UHF on all channels it's no longer relevant.

[1] Memory nudged, so I had a look at mine; it's a boxy dipole with twin vertical reflectors.