FAQ: Analogue, DTT, Aerials

Tom Slick

watty wrote: »

Discussed earlier,

1) It doesn't work any better than a 6 Euro indoor aerial in Euro bargain store
2) Only any use inside attic. One puff of wind and it falls to bits.
3) The five "directors" are badly designed and thus makes virtually no difference if they all removed.

All these "X-beam" aerials look the same to me.How are the directors badly designed?

DSOMAN

Tom Slick wrote: »

All these "X-beam" aerials look the same to me.How are the directors badly designed?

Inverse Square Law - There's such a thing as too much metal in the capture area of a yagi type aerial. They tend to widen the gain curve out, if you're using a "grouped transmitter" and your local aerial installer has fitted a Tri-boom or "X type Wideband High Gain" aerial to impress you chances are when we put the Tx's on reduced power you're going to have problems.

Divis is a good example of what not to install when trying to get the best results from an aerial, i see in NI "High Gain Wideband" aerials for a Group A/ K Transmitter when they're not designed to work over those frequencies.

STB

DSOMAN wrote: »

and your local aerial installer has fitted a Tri-boom or "X type Wideband High Gain" aerial to impress you chances are when we put the Tx's on reduced power you're going to have problems.

Which side of the border ?

watty

See http://www.boards.ie/vbulletin/showpost.php?p=67952689&postcount=38

DSOMAN

This is as much about standards, and the compromises we are prepared to tolerate, as anything. It's as much philosophy as science! My gut reaction is that we should not suggest to anyone that they should attempt to use an aerial of the wrong group. A big advantage of that is that it would keep things simple. However, we must be pragmatic and consider the following facts:

1. Replacement of an aerial for one of a different group will probably end up with the whole thing being replaced, so the cost could be £150. That certainly suggests to me that the advice should be 'suck it and see' if there's a significant chance of an old grouped aerial working. But of course advice all along has been 'don't be hassled into buying a new aerial, wait until after DSO and then suck it and see.' After all, we are only talking about people missing out on the COM channels here; they are almost certain to get the PSB stuff on their old aerial, and it would make sense to buy a new aerial once all the dust has settled and the riggers, having had their bonanza, have drunk all the profits and are once again reduced to penury and begging in the streets.

2. Historically our abhorrence of the use of aerials of the incorrect group is based largely on the likelihood of ghosting, which is not an issue with DTT (but CCI is of course).

3. In the post-DSO world anyone who has been using an old aerial
successfully to receive in-group DTT will have perhaps 10dB more signal than they need (so to speak) on the in-group channels. All other things being equal, that 10dB could well equal the gain difference of the aerial between in-group and out-of-group signals. This applies particularly when the out-of-group signals are LF of the group, for reasons of cable performance, yagi behaviour, and propagation. Post-DSO will never, allegedly, have half power tx working.

I have never experimented with the out-of-group response of
aerials. As my GP said when I asked him about the use of time-expired drugs, "I don't know because no-one's ever done the research, because it's just basically a very daft idea." However, I can generalise.

4. 1. The response of Gp A aerials is really very poor above channel 42. I'd say that we could never suggest that a Group A would be any good for the top of Gp B or Gp CD.
2. The response of a Gp B aerial is likely to be very poor above ch58. Again, it's a no-go.
3. The response of a Gp B aerial can be perhaps only 7dB down on ch31, but ch21 would be problematic. Many years ago when the Emley Moor mast fell down half the inhabitants of Doncaster turned their GpB aerials to Belmont, and most received a slightly grainy but watchable BBC2 on ch28. A lot of these
aerials were not replaced until BBC1 started from Belmont on ch22, and actually some are still in use. No doubt the owners were well pleased when they bought DTT and found it worked better than analogue ever had!
4. Gp CD aerials seem to work fairly well down to ch44, but fall off badly in Gp A. However, it's interesting that a great many Waltham viewers with GpCD aerials have good reception of analogue C5 on ch35 and even of the Gp A muxes. In Mansfield this is very common indeed. It's the result of propagation differences mostly, Waltham C5 appearing here in S Yorkshire good 10dB above the Gp CD analogues.

lucernarian

I'm afraid digital spy is over here

rebeve

Living in the Kilworth co Cork .Very poor reception on rte 1 and 2 .Tv3 and the rest ok ,so anyone recommend a decent vhf aerial.
Thx

STB

Have you tried DTT rebeve ? Dont go buying a VHF aerial now.

rebeve

STB wrote: »

Have you tried DTT rebeve ? Dont go buying a VHF aerial now.

Have `nt tried anything yet .I use freesat , but my rte 1 and 2 has degraded over time, now its very bad .I went up on the roof yesterday and stood next to the aerial and touched the last reflector the picture was now perfect .But when I move away from the aerial the picture gets very bad again . Tv3 is fine on UHF .Both aerials are pointing towards mullinganish I presume.Dont really know anything about dtt.
Slan

STB

rebeve wrote: »

Have `nt tried anything yet .I use freesat , but my rte 1 and 2 has degraded over time, now its very bad .I went up on the roof yesterday and stood next to the aerial and touched the last reflector the picture was now perfect .But when I move away from the aerial the picture gets very bad again . Tv3 is fine on UHF .Both aerials are pointing towards mullinganish I presume.Dont really know anything about dtt.
Slan

What type TV do you have ? Model No ?

DTT is Digital Terrestrial Television = clear. no snowy reception like satellite quality. Its on at the moment!

Do not buy a VHF aerial. Short life span as analogue will be turned off in favour of DTT which used UHF.

rebeve

STB wrote: »

What type TV do you have ? Model No ?

DTT is Digital Terrestrial Television = clear. no snowy reception like satellite quality. Its on at the moment!

Do not buy a VHF aerial. Short life span as analogue will be turned off in favour of DTT which used UHF.

Its a tevion flat screen bought it about 6 months ago in Aldi . So if I buy a dtt aerial I should pick up rte etc .Thanks for the help STB
Slan
Conor

watty

Lidl next week selling TVs that are only monitors.

Aldi and Lidl Digital TVs (sold up to end Sept 2010 so far) are useless for the Irish market. They are only for UK digital.

They are not that cheap anymore either.

STB

rebeve wrote: »

Its a tevion flat screen bought it about 6 months ago in Aldi . So if I buy a dtt aerial I should pick up rte etc .Thanks for the help STB
Slan
Conor

No you will a set top box for DTT. Some not all TVs have MPEG4 tuners. Yours doesnt. If it had you wouldnt need a set top box for Irish DTT.

Your existing aerial will be fine probably.

Infact if you do a scan on the digital tuner of your TV it should find the DTT stations. Unfortunately you will get just sound on the channels and no picture as your TV isnt MPEG4. But if you at least ppick up the stations it will mean that you just need a set top box.

rebeve

STB wrote: »

No you will a set top box for DTT. Some not all TVs have MPEG4 tuners. Yours doesnt. If it had you wouldnt need a set top box for Irish DTT.

Your existing aerial will be fine probably.

Infact if you do a scan on the digital tuner of your TV it should find the DTT stations. Unfortunately you will get just sound on the channels and no picture as your TV isnt MPEG4. But if you at least ppick up the stations it will mean that you just need a set top box.

I only get a picture on rte 1 or 2 if I stand on the roof and hold the last reflector on the aerial, when I move away the picture gets snowy

Tom Slick

If that's analogue VHF RTE from Mullaghanish, it has nothing whatsoever to do with digital reception.

rebeve

Tom Slick wrote: »

If that's analogue VHF RTE from Mullaghanish, it has nothing whatsoever to do with digital reception.

Ya but I am trying to figure if my analogue aerial is fecked .

Tom Slick

Stop quoting the posts about DTT, then.
If your aerial is behaving like that, then there must be something loose/broken. (even the cable connection)

rebeve

Tom Slick wrote: »

Stop quoting the posts about DTT, then.
If your aerial is behaving like that, then there must be something loose/broken. (even the cable connection)

No sh1t Sherlock

Tom Slick

Why did you ask if you had it all figured out yourself?

watty

There is no such thing as analogue or digital aerials.

There are HF, VHF, UHF aerials.

Tom Slick

I took it that Eve was referring to her VHF aerial.

rebeve

Tom Slick wrote: »

I took it that he was referring to his VHF aerial.

Who said I was a he .

rebeve

watty wrote: »

There is no such thing as analogue or digital aerials.

There are HF, VHF, UHF aerials.

Thx for That .

Sam the Aerialman

You should be asking why a balun appears to broaden the response of an aerial?

It's interesting and a bit amusing that Gp B aerials can outperform a wideband
in Gp A. After years of moaning about the unnecessary use of wideband aerials,
and being called a fool for it by many riggers, I feel almost vindicated.

watty

Wide band yagi's don't do Group A (up to 9dB less at Ch21, typically 6dB less). Only a Log Periodic will "really" do Ch 21 to Ch 28. I hope to update this more soon http://www.techtir.ie/radio-tv/uhf-aerials
@ Sam the Aerialman Interested in contributing?

of course a Group B will work better on Group A than most WB aerials.

EdRey

I've read through the thread and lots of people asking which aerial is good for Dundalk, Dublin and Dingle, so I'm going to throw my hat in the ring and ask which one is good for Limerick?

I'm planning to put in in the attic, and I'm looking at this one:

http://www.tvtrade.ie/yellow-group-b-uhf-aerial.html

Reception wise (DTT), I'm not sure how strong my area is (Dooradoyle), but the back of the house faces north. I assume Woodcock Hill is my transmitter? BTW I'm using PlayTV at decoder.

Comments very welcome

watty

Yes, Woodcock hill, Group B. If you have a decent view of the mast then ANY group UHF aerial probably works.

babo9

brian ireland wrote: »

Will this work? Its reduced from 40 to 9 euro in argos
http://www.argos.ie/static/Product/partNumber/9239690/c_1/1%7Ccategory_root%7CHome%2Bentertainment%2Band%2Bsat%2Bnav%7C14419512/c_2/2%7Ccat_14419512%7CClearance%2BHome%2Bentertainment%2Band%2Bsat%2Bnav%7C14520847.htm

Was about to buy that today until I saw the comments here!
What about this one? Apologies if it's been discussed before but can't find it!
23.99 down from 79.99.
http://www.argos.ie/static/Product/partNumber/9239717/Trail/searchtext%3EUHF.htm

Tom Slick

The general consensus here seems to be that Argos aerials are no good.

Depending on where you are/what your signals like, something smaller and tidier looking might work. The huge drop in price probably says it all . . .

watty

Argos aerials are mostly overpriced Junk
That looks like a cheap copy of a Televes DAT75.

It depends where you are as to how big (how much gain) of aerial you need.

You are best to buy aerials from a proper supplier, not general retailer where you pay x2 to x4 for poor design.