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Aerial groups - new feature

There has been a lot of debate about aerial "groups" over the last few years...

There has been a lot of debate about aerial groups over the l
Published on by on UK Free TV

In the olden days of black and white, 405-line television, when the frequencies used were "very high" (VHF), the UK two-channel television service was provided using a just 100 transmitters and reception needed a standard aerial.

Later the system was upgraded to "ultra high frequencies" (UHF) for colour and now uses over 1,120 transmitters with more channels on more frequencies.

To enable the best quality reception possible, UHF television aerials are produced in a number of "groups". Each group is designed to operate on a range of channels, blocking all others. This is to prevent interference from "other" transmitters and to decrease losses on those required.

Each group is designated a colour, which is used to mark the aerial. Whilst wideband (black) aerials are designed to receive on all frequencies, their performance can be below a grouped aerial.

The transmitter pages now show a table like this:



The three sections show the three phases. The first is that before digital TV was introduced. This example shows that a group A (red) aerial would have received the original four channels but a group K was required to also receive FIVE. The channel number for FIVE on analogue is shown with an asterisk because it is "out of designated group", group A.

The second section shows the "digital with analogue" phase, where the transmitter has the analogue services from above with the new low power digital services. It can be clearly seen that on this transmitter a group A aerial will not receive any digital services at all, and that even a group K aerial will not receive the multiplex B service on C67. The only choice for digital reception here is a wideband (black) aerial because it is the only coloured band that crosses from left to right.

(You can also see that some of the digital services have plus and minus symbols. This indicates these transmissions use a 166.67kHz offset.)

The final section shows the designated frequencies that will be used for digital television after switchover. Whilst the public service multiplexes BBCA, BBCB, D3+4 are back "in group" (group A), to receive all the multiplexes, including the two potential new ones, the only choice here is wideband.

The performance of grouped aerials for each transmission channel was defined by the old Independent Television Commission (ITC) and is:



The larger the value, the lower the signal level possible.







Your comments: most recent posts are at the bottom


Your comments are always welcome. Please use the form below to add your thoughts or questions to this page. We will get back to you as soon as we can.

S
Stephen Phillips
Thursday 12 March 2009 10:27AM Nuneaton
When you sat 100/1120 TRANSMITTERS are you counting locations, or actual transmitters, one per frequency?
Briantist
Thursday 12 March 2009 11:16AM
Stephen Phillips: In this context it is masts.

There were 74 BBC VHF transmitter elements, 40 ITV VHF transmitter elements on 102 sites.

There are 1,129 UHF transmitter sites, 80 carry also carry six digital multiplexes and 55 have analogue FIVE, 8 have only analogue FIVE.

Roughly, that's 4,540 analogue transmitter elements plus 480 DVB-T elements.

After switchover there will be around 3,646 transmitter elements on around 1,117 sites.
C
Chrism
Thursday 12 March 2009 2:32PM Cambridge
Brian, our transmitter is Sandy Heath (conveniently, the one you've used in your example above). Even with a wideband aerial, we suffer from poor MuxB (Channel 67) performance. Given that we don't watch analogue any more, and digital switchover is still over 2 years away round here, would it be worth installing a group E (C35-C68) aerial to get better C67 performance?
I
Iain Davies
Thursday 12 March 2009 3:15PM Weston-super-mare
As I have commented before, if you can use a "grouped" aerial for Freeview use one as the gain is higher, the bandwidth and directional properties (to reject unwanted signals) are all better than wideband aerials.
J
Jordy
Friday 13 March 2009 4:27PM
Alright gents - Yes there has been a lot of debate over the years with regard to aerial groups and a good piece by the way Brian... Iain what is you say is correct but i'm gonna throw a spanner into the works and what Nero Aerials has pointed out to me and quite rightly so is unfortunately wideband aerials are going to have to be the way forward from here in certain if not most areas, take an area like North Staff's were reception is decided by what street you live on, the same can be said for Ballymena. Which depending on what street you live you get Limavady or Divis and i'm quite sure there are many examples up and down the land... Darvel, Blackhill, Rosneath is another... Another twist in the tail is the group A transmitter broadcasting in the low mhz, widebands can't cope with low channeled muxes they drop off to quickly up the gain, flatline then you have to masthead them and overload occurs and and excellent point that was made to me was Do we do away with the masthead amp?, will DTT not overload them...
Briantist
Friday 13 March 2009 4:48PM
Chrism: If you do install a group E aerial, then you will block out the three public service multiplexes at switchover, and possibly one other!

The example I used was Sandy Heath because this is one of the most complicated transmitters...

If you have problems with Mux B you may just have a local interference problem, www.ukfree.tv link icon Single frequency interference | ukfree.tv - independent digital television and switchover advice, since 2002
Mark Aberfan Aerials
Friday 13 March 2009 7:27PM
Hi Guys,

I take the attitude that on group a transmitters of which i have two on my doorstep one digital (aberdare) & one still ani (merthyr tydfil) that unless requested otherwise i fit group a aerials, both transmitters will still be group a after switchover this is my reasoning, The primary reason for a customer to have a tv aerial fitted is to receive tv, not some mythical service that may or may not appear in the future, so to get them the best signal at the minimum cost a group a is the one for the job. To get anywhere near the same gain on a wideband aerial, it would need to be a lot larger (2 to 3 times) or over amplified which may cause other problems & introduce noise. a larger wideband aerial will not only cost more but require larger bracketry & mast all adding to the cost to the customer. So the customer would in my opinion would have to pay more for us to do a rig that goes against all the rules of a good install, i know some big companies view this as profit option & that keeping in stock only widebands makes their lives easier & cheaper, but it dont sit right with me.

Mark Aberfan Aerials
C
Chrism
Friday 13 March 2009 8:07PM Sheffield
brian, no, no, only until switchover then I would reconnect the wideband one! On that basis, what do you think of the band E aerial? Don't forget I've got over 2 years of inadequate service ahead of me...
S
Sally
Friday 13 March 2009 8:31PM Armagh
Hi Guys,

First post, be gentle :)

We have a Sony Bravia with built in freeview.

Two problems ..... in recent weeks we can't get BBC1 or BBC2 digital. Was fine until a few weeks ago. An automatic scan won't pick them up but a manual does, even though its unwatchable and pixelated. Has something changed recently?

Problem 2 - We've never been able to get Mux C (Sky et al) at all, either through Bravia or set-top box. Are we just out of range?

Post Code BT61 9QX pulling from Divis.

Thanks for any advice. :)
Mark Aberfan Aerials
Friday 13 March 2009 8:41PM
Hi Sally,

keep a eye on this thread, with a bit of luck jordy who has local knowledge will be along to give you advice.

Mark Aberfan Aerials
S
Sally
Friday 13 March 2009 8:48PM Armagh
Thanks, Mark, will do :)
J
Jordy
Saturday 14 March 2009 1:29AM
Hi Sally.
I'm an installer in Northern Ireland based around the Dromore direction. It's Richill you're close to... You're slightly out of range out of Divis DTT hence the powerful relay in Armagh... I'm not surprised Mux C dropped off which is channel 48 you must have a group A aerial which meant you never got mux C... You've been able to fine tune the BBC channels but they have not locked to your set top box... A masthead amp may improve the situation but unfortunately the IBA put a relay in Armagh for a reason... I apologise if i've used any language you do not understand. Please do not be afraid to ask...
J
Jordy
Saturday 14 March 2009 1:38AM
Mark - How's the form mate? How's business for you... Was in Bristol there for a few days for a wedding... I truly don't envy what you do down there driving through those valleys, your head must be cut! What's your take on the future of masthead amp's?
Briantist
Saturday 14 March 2009 8:41AM
Chrism: It's probably worth a try as long as you don't mind having to store and reconnect your current one!
Mark Aberfan Aerials
Saturday 14 March 2009 9:31AM
Hi Jordy,

I know what you mean about the valleys, i can be 1 mile away from where i need to be, but have to drive 10 miles to get there !

I think there is a future for mastheads, in my area where there are loads of relays transmitting only half the freeview service, i think a lot of people will want out of area full service from wenvoe & mendips, maybe using grouped mastheads would reduce unwanted over amplification of unwanted services, the selling of the middle part of the band (for undisclosed other uses) wont help & could themselves become a source of unwanted interferance, more so when amplified. It would of made more sense to have sold the bottom of group a or the top of group c/d, a masthead with the sold off channels filtered out could be one answer if it becomes a problem.

Mark Aberfan Aerials
S
Sally
Saturday 14 March 2009 10:22AM Armagh
Hi Jordy,

Thanks for your comments.

We did get BBC1 & BBC2 on the Bravia up until a few weeks ago - its was always a bit flaky but not its unwatchable. The aerial was upgraded to a digital aerial about a year ago by a reputable company in Armagh - is there anything I can check to see what aerial we've now got? There's a red box on my aerial mast which has been there 10 years, so I think I've already got a masthead amp. Any suggestions woud be welcome! Thanks

Sal
J
Jordy
Saturday 14 March 2009 10:56AM
Hi Sally -
Please feel to give me a ring 07734819604. I will see if i can give you some help over the phone.
J
Jordy
Sunday 15 March 2009 10:25AM
Sally - I very much hope that reputable company in Armagh informed you that is there no such thing as a digital aerial... You can get a pair of binoculars and see what coloured tip is on your aerial red is A, black is wideband that is of course if you have no access to the aerial. The red box is a masthead amp when the installers put up your rig i imagine the db (reception) was fairly low mid 40's... In my opinion i'd go straight for the masthead amp and that's were the problem lies... Do you have an RTE aerial?
C
colin
Tuesday 17 March 2009 9:06AM
Clearly nowhere near enough power is being transmitted anywhere.
R
Robin
Friday 20 March 2009 10:27PM
Can I suggest the following solution for Sandy Heath? Retain the existing Group A aerial to optimise C4 on Ch21 and combine it with a Group E (plus amplifier if improvement needed and possible). Post changeover - or at switchoveer if waiting for this before going digital - replace the Group E aerial with a Group B with 3db more gain thean the Group A one thus the input to the recieveer will be uniform accross all channels. A similar solution may also be possible whenever it provides improvement relative to a wide band aerial? Would the availability of a narrower band aerial designed for channels 40 to 52 only be cost effective because a smaller - thus less costly - aerial would be needed for any given gain? There are a lot of homes within the Sandy Heath coverage area!
C
Corin
Tuesday 14 April 2009 12:58PM
Trying to reach this page from the

UK Free TV Latest

right hand menu box generates an incorrect URL of

www.ukfree.tv link icon http://www.ukfree.tv/tran…1549

and the resultant 404 Error Not Found.


S
steve
Tuesday 14 April 2009 2:50PM Nuneaton
Zut alors!
D
Derek Dray
Sunday 3 May 2009 10:04AM
Why has ITV stopped tranmitting in Eastbourne (2 day's now).
S
steve
Sunday 3 May 2009 11:15AM Nuneaton
Lost interest in the geriatric market?

Are both analogue and digital off? Other channels on same mux off?
M
michael scott
Wednesday 6 May 2009 11:38PM
I am amazed how many people in the industry are recommending only wideband television aerials as a simplistic,and rewarding,non-answer to a DSO complex geographic situation.
I went last year to one of the biggest international wholesalers nearby to purchase a group E aerial:"no mate we don't have one,all you need is a wideband one" !!!!!.
Where ignorance is bliss it is folly to be wise......
E
Ernest Jones
Thursday 11 June 2009 11:48AM Llanrwst
We were in LLanrwst the other week for our holidays and we were just a few miles from the Bettws-y-Coed mast, in fact we could see it from our campsite. I pointed the aerial(Vertically) straight at the mast but the picture was terrible. I tried to use my laptop with a dongle but did not get one channel.
We go every year to this particular campsite so I hope things improve enormously by next year.
S
Stephen Phillips
Friday 12 June 2009 5:09PM Llanrwst
B-y-c does not transmit digital so far as I can tell from info here!

Try putting the campite's postode in the box.
I
Iain Davies
Saturday 13 June 2009 5:57PM Haverfordwest
As I have said before,only use a wideband aerial if you have to, due to "out of group" channels.If your transmitter's channels are in a group,use a grouped aerial as the bandwidth,directivity and gain are far better than a wideband aerial.
D
David
Sunday 13 February 2011 6:12PM
Does anybody know about the little red box at the bottom of analogue aerials? are they obtainable if damaged and do we actually need it?
Briantist
Sunday 13 February 2011 6:40PM
David: OK, an aerial is an aerial is an aerial. They are not "analogue" or "digital".

There are plenty of things a "red box" could be, what is inside?
Mark Aberfan Aerials
Sunday 13 February 2011 8:26PM
Hi Guys,

It might be a group a masthead, I seem to remember mastheads with group colours in the distant past ! if it is a group a masthead then yes they are still available but only in black !

Mark Aberfan Aerials
C
Chrism
Monday 14 February 2011 3:17PM Sheffield
Long time since I last posted on here. Back in March 2009 my problem (on the west side of Cambridge) was the MuxB/C67 signal from Sandy Heath, which was dreadful. Now, with a month or 2 to go until Sandy Heath cutover, C67 is the best and most reliable, and Mux 1/C42 and MuxC/C40 are the poorest, on a consistent basis; seems to me they've rearranged the transmitter in some way over the last year and a half. Ideas? Anyway, my real question was:- do I need to know about the +/- offset of some Muxes, as there doesn't seem to be any fine-tuning available on any freeview box I've ever owned?
Briantist
Monday 14 February 2011 3:41PM
Chrism: No, you don't need to use the offsets, your equipment will automatically check them.

J
John
Sunday 10 April 2011 10:49PM Belvedere
Can anyone help me please?

I have bought Sony tv with HD freeview but I can only get freeview channels and not HD channels when auto and manual tuning channel 30. I live in DA17 area so crystal palace mast. some freeview channels have poor signal but most are fine. Aerial is in my loft.

Can anyone help please?
M
Mike Dimmick
Sunday 10 April 2011 11:12PM Reading
John: Pre-switchover HD services are on C31. C30 will be used after switchover - that's currently Channel 4 analogue. You have a pretty good chance of getting HD services now, but not quite as good as the other multiplexes. If you're having trouble with some others, your TV may not be able to see the HD services.

Do check that there is a Freeview HD logo on the TV, and that the manual says it supports DVB-T2. If it just says 'HD Ready' you'll need an external Freeview HD decoder.
J
John
Monday 11 April 2011 1:11AM Belvedere
Yes, it is HD Freeview TV with DVB-T2, and I cant get HD channels on 31.

What can I do please?
A
Andy
Sunday 10 July 2011 7:10PM Edinburgh
Anybody any idea about Edinburgh? Blackhill or Craigkelly? Seems to depend on where you read it.
J
jb38
Sunday 10 July 2011 9:29PM
Andy: Well, the trade predictor indicates Blackhill as being your No1 choice with good reception across the board being seen.

Craigkelly being the second best, but with the problem that only the first three Mux's are considered as being viewable, these covering the main BBC & ITV channels, including the HD one.

It should be said that although the predictor used is reasonably accurate local conditions can upset what is indicated as being possible, and in area's such as anywhere near Dalry Road or similar chimney mounting is really an essential for reliable reception, although a test with the aerial in the loft could be worth a try.
J
jb38
Monday 11 July 2011 7:40AM
Andy: Forgot to add to what was said re you including Edinburgh in the list, that there is a very low powered dual polarity fill in transmitter called Canongate (@ 2 miles from you) transmitting on channels 55-50-59, but its very doubtful if you would receive that in your location, and of course it isn't even mentioned as being a possibility on the trade predictor.
D
Dean Gerstel
Thursday 29 September 2011 2:04PM Barnsley
Hi. My neighbour recently fitted a new external aerial to another neighbours house. At the same time as switch over the old lady swapped her rented tv for another rented tv, but this time one with built in Freeview. This is a Linsar 19LED504.
We live in Hoyland, Barnsley. Our post code is S74 9LR. The aerial that was fitted appears to be a wide band aerial, although I am not entirely sure. The elemants are vertical and it is pointing I believe at Sheffield(Crosspool). There is no line of sight. There is a hill lined with trees about 5 miles away from us and blocking the line of sight. Its is definatly not pointing at Emley Moor.
Anyway the lady's TV keeps getting pixelation and often drops channels, from memory she keeps losing ITV2 and some other non BBC Channels.
I have twice retuned the TV shortly after dropping channels and folling retune the tv finds the missing channels. Why would this be? At first I thought the problem may be co-channel interference. But not so sure now. I have wondered how crucial alignment is. This website says that we are 14 miles away from crosspool transmitter and I was wondering if because you can not see the transmitter to point the aerial at it, if this was the problem. But then why would it find the dropped channels after re-tuning?
Please Help
Many Thanks
J
jb38
Thursday 29 September 2011 5:31PM
Dean Gerstel: You have to carry out a signal check (via tuning menu) to verify what station is being received, this done whilst on BBC1 noting the Mux channel associated with it, then change to ITV1 (ITV2 also on this Mux) and do similar.

If Sheffield (BBC1) Mux Ch 21 - (ITV1) Mux Ch24, whereas if its Emley Moor (BBC1) Mux Ch47 - (ITV1) Mux Ch44.

Unless there is some large obstruction between you and Emley Moor (@12mls) then Emley would appear as a better bet than Sheffield (@ 9mls) Emley Moor being massively more powerful.

Trees can be dastardly as far as reception is concerned, and if they are obstructing a transmitter that's on relatively low power anyway the more of an effect they will have, Sheffield being on 1Kw compared to Emley Moor on 174Kw.

By the way Emley is 308 Degrees - Sheffield being 201.
I
IanP
Friday 11 November 2011 1:05PM Plymouth
I have changed from Ivybridge to Caradon Hill transmitter. Tuning the TV gives excellent reception on all channels (105 channels detected) EXCEPT the BBC channels.
The BBC chanels come up on the display, but say "no signal" When checking signal strength on ITV, it shows full strength, but when on BBC it shows nothing.
Any help on this would be appreiated.
Briantist
Friday 11 November 2011 1:18PM
IanP: Can you please, in the first instance, see the Single frequency interference | ukfree.tv - independent free digital TV advice page?
A
andrew brown
Saturday 8 December 2012 2:45PM Cinderford
Has anyone noticed how difficult it is to get hold of grouped aerials these days?
B
Bill
Saturday 22 December 2012 3:37PM
Is there any planned increase in the number of freeview channels available at the Findon Meridian Transmitter?
Dave Lindsay
Saturday 22 December 2012 3:38PM
Bill: No, it isn't likely at all!

See:

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