UHF Aerial groups (Why C/D) ?

Ulsterman 1690

OK so weve all heard of aerial groups

Ch21 to Ch37 Group A RED
Ch35 to Ch53 Group B YELLOW
Ch48 to Ch68 Group C/D GREEN
Ch35 to Ch68 Group E BROWN
Ch21 to Ch48 Group K GREY
Ch21 to Ch68 Group W BLACK

But why is the middle one called "Group C/D" presumably its a combination of "Group C" and "Group D" but when/where did it originate and what were the channel ranges/colour codes for C and D ?

lawhec

I believe it's down to a couple of factors.

1. Seperate group C and Group D aerials did exist for a short time but channel allocations being what they were (especially when BBC1 and ITV started on UHF in late 1969) the channel allocations on the high end of the UHF band didn't suit either group and therefore they were combined into Group C/D.

On a very rough memory Group C covered E48-E60 and Group D E55-E68.

2. The original Stockholm 61 plan to allocate UHF frequencies for TV did go up to frequencies of around 950MHz (as opposed to 854MHz right now) and the original plan for Group C and Group D "groupings" were much wider than what they became because the UHF broadcast band was very shortly cut to 854Mhz. My guess is at the time the countries thought that they wouldn't need so much bandwidth for future services therefore sacrificed the top end for future use which nowadays includes GSM mobile phones. Certainly if these frequencies had still been available for TV use Channel 5 could have had full UHF coverage in the UK, DTT would also have better coverage etc. but that's all hindsight.

Ulsterman 1690

The original Stockholm 61 plan to allocate UHF frequencies for TV did go up to frequencies of around 950MHz....countries thought that they wouldn't need so much bandwidth for future services therefore sacrificed the top end for future use which nowadays includes GSM mobile phones.

Good point The US initially went for the for 470-890MHz (Channels 21-83) then lobbed off 70-83 for (among other things) analouge callphones 14-20 for two way radio and are talking about taking away a few more channels (as are the UK) after the analouge switchoff

LOTTOWINNER

I don't want to sound like I'm sucking up! But you two guys certainly know your stuff, I've read numerous replies to questions from both of you and I'm always impressed by how detailed and easy to understand the threads are!
Keep up the good work lads.

Ulsterman 1690

Aw shucks

but Dont forget Tony (pretty knowledgable on satellite stuff) and Watty (general RF comms) as well

watty

Thanks.. Next time I'm visting the folks on GI land I'll think of you.

Must be the high quality of Northern Education

Ulsterman 1690

Came across the answer to the original question herehttp://www.pembers.freeserve.co.uk/World-TV-Standards/Transmission-Systems.html if anyones interested

.....therefore only three sizes of aerial needed to be manufactured, and these were called
Group A, marked red, channels 21-34,
Group B, marked yellow, channels 39-51 and
Group C, marked green, channels 52-68.

As the network spread, however, it became necessary to depart from the nine clusters, and use a channel-spread greater than ten at some transmitters. Further aerial groups were added:
Group D, marked blue, channels 49-68 and
Group E, marked brown, channels 39-68.

Group C was changed to cover channels 50-66 before Groups C and D were eventually merged to give Group C/D, marked green, channels 48-68.

Group K, marked grey, channels 21-48, is used widely on the Continent, but also suits some UK situations.

When the fifth uhf network, Channel Five, began broadcasting in 1997, using mainly the previously vacant channels 35 and 37, aerial Groups A, B and E were enlarged so that all could receive those channels

Antenna

What European countries use UHF channel 69 for TV?

In this country it is used by some licenced 'deflectors', but not by any of the national networks.

In the UK - it is not used. (Ch69, if it had been made available for UK TV transmission, would obviously have been very useful to 'Channel Five' for transmission in many of the areas that are group C/D for the 4 main networks.)

what about elsewhere?

lawhec

Antenna wrote:

What European countries use UHF channel 69 for TV?

In this country it is used by some licenced 'deflectors', but not by any of the national networks.

In the UK - it is not used. (Ch69, if it had been made available for UK TV transmission, would obviously have been very useful to 'Channel Five' for transmission in many of the areas that are group C/D for the 4 main networks.)

what about elsewhere?

According to the article that Ulsterman linked to, it has been used in Switzerland. I think I remember it being used in Austria too. It has also been used for DTT in Spain.

I like Channel 69 (ooh, err! ) as for a UHF distrubution system its a clear channel provided you don't receive RTÉ from Clermont Carn or Maghera (or any station on channels 67 or 68).

Hissing Sideban

Heres a link to a site which for TV aerial anoraks (like me!)

Full of interesting info and pictures!

http://www.wrightsaerials.tv/

byte

Hissing Sideban wrote:

Heres a link to a site which for TV aerial anoraks (like me!)

Full of interesting info and pictures!

http://www.wrightsaerials.tv/

Great site there Hissing Sideban. Makes some interesting reading!