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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 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.

Help with Freeview, aerials?
Can I attach a Freeview digibox to a Combi TV/Video unit?1
My high gain aerial can't get all the Freeview channels I expected2
I can't get Freeview yet, when will it start in my area?3
Are there plans to extend the range of regional variations on Freeview?4
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In this section
Help receiving BBC TV - Transmitter work2
List of digital switchover exceptions 3
Brierley Hill transmitter all TV services 8am-6pm, 2nd February4
List of all UK TV transmitters5
Freeview search by frequency6

Tuesday, 29 November 2016
10:58 AM

Brian Scott: You can check the transmitter for yourself, but its unlikely. Everyone blames the transmitter or the weather, but its seldom the case.

On the other hand, the thin bit of coax cable that makes your system work is highly likely to suffer from the effects of the weather, old age or simply falling of the back of the TV.

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MikeB's 2,559 posts Platinum Platinum GB
Friday, 23 February 2018
David Bascombe
10:26 AM Lyndhurst

how do you position roof aerial to get better picture quality without tech stuff??????

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David Bascombe's 1 post GB
10:50 AM

David Bascombe: Use a compass to aim the aerial in the direction of the transmitter and use a signal meter to make fine adjustments until you find the sweet spot with the best signal strength.

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StevensOnln1's 2,221 posts Platinum Platinum GB
Tuesday, 10 April 2018
leonard Horsfall
9:16 AM

I would like to know the grouping of my local transmitter which is Mankinholes Transmitter in Todmorden

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leonard Horsfall's 1 post GB
12:06 PM

leonard Horsfall: Todmorden is current a Group B transmitter, however if you are having a new aerial it would be advisable to fit a wideband type in most instances in order to ensure your aerial will remain suitable for any future frequency changes.

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StevensOnln1's 2,221 posts Platinum Platinum GB
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