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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Alarms, Phones, Aerials, CCTV & Datacomms >> Digital switch over https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1252404059 Message started by CWatters on Sep 8^th, 2009, 11:00am

Title: Digital switch over
Post by CWatters on Sep 8^th, 2009, 11:00am

So you think changing your aerial is a problem... Nice photos here of an upgrade being done to our local transmitter....

http://tx.mb21.co.uk/gallery/sandyheath/dso/index.php

Title: Re: Digital switch over
Post by londonman on Sep 9^th, 2009, 10:55am

Great site..thanks for that. Reminds me why I always stuck to baseband! None of that RF trickery for me.

Did you lose signal while the work was going on?

Title: Re: Digital switch over
Post by big_all on Sep 9^th, 2009, 11:33am

its worth mentioning that each picture is an album on its own so theres around 90 pictures there

Title: Re: Digital switch over
Post by Joiner on Sep 9^th, 2009, 12:51pm

That chopper got around a bit!

http://news.bbc.co.uk/local/shropshire/hi/tv_and_radio/newsid_8237000/8237051.stm

Title: Re: Digital switch over
Post by Lectrician on Sep 9^th, 2009, 6:47pm

Well, they did our masts with good old fashioned ropes and pulleys!

Title: Re: Digital switch over
Post by CWatters on Sep 9^th, 2009, 6:48pm

londonman wrote on Sep 9^th, 2009, 10:55am:

Did you lose signal while the work was going on?

Not that I can recall but I don't watch daytime TV much.

Sandy Heath is on slightly reduced power this week and some people have reported problems with the low power muxes (Ch4 and ITV) so looks like some more work being done.

Title: Re: Digital switch over
Post by Lectrician on Sep 9^th, 2009, 8:32pm

As far as I know, they fit the reserve digital transmitter lower down the mast (to be used when the main top transmitter is being serviced etc). This transmitter can be switched on and the main one turned off without loss of service - just a 'blip' or 'chirp' from your set.

The lower reserve transmitter (digital) is used for a short time to transmit the analouge while the top main transmitter is replaced. The current digitial signals are being transmitted by even lower transmitters on the mast while all this work is going on, these have been inplace for years and are what transmit the digital signals while the analouge is still on, they are only low powered and where only ever temporary.....for years. (hence the digital signals being low in all areas while analouge is still around).

Once a mast switches off analouge (being transmitted through the new top main digital transmitter), this top main transmitter then transmits the digital, still at a lower power, until all other in area transmitters are switched over, when the power will then be increased to the maximum.

Title: Re: Digital switch over
Post by CWatters on Sep 9^th, 2009, 11:10pm

Yes exactly. One of the main reasons the digital transmitters are on low power is to avoid interference with analogue and digital transmitters in other areas.

Years ago it was thought that the available TV spectrum was full - each TV frequency was already being reused something like 40 times elsewhere around the country. You may recall that to fit in Channel 5 they had to use frequencies normally reserved for the UHF output of VCRs and computer games (It cost channel 5 something like £150 million to retune them all to free up capacity). They also had to move some aircraft radar to other channels.... Yet despite this they still managed work out how to fit in enough to allow extra frequencies to allow dual running in most areas during the changeover.

Title: Re: Digital switch over
Post by Joiner on Dec 20^th, 2009, 10:49am

We're experiencing horrendous problems with (some) Freeview channels, ironically mostly with what are the "terrestrial" channels, 3, 4, and 5, which have vanished completely. We've got a 42" Samsung with all the bells and whistles and, following an earlier post when Cwatters told me that the signal from Sutton Coldfield was crap at the best of times, we've had two aerial blokes here who have, variously, replaced old cables and fitted a line-booster, both of which worked for about a day and then might just as well not have been there.

To watch 3, 4, or 5, we have to go through the recorder and watch via terrestrial and its rubbish picture quality.

I've gone through the channel search procedure many times (about once a day, in the vain hope that whoever threw the switch on the transmitter originally would realise what he'd done and put it back again) but those channels are still nowhere to be found. What can be had is so badly pixellated (with broken audio to boot) that they're unwatchable.

Yet all the BBC channels are fine. What do they know that the commercial operators don't??

With the full switch over so far away we're now seriously considering going the satellite route, which I've always resisted on principle - why pay for more channels when we only watch a fraction of what we can get now for free (OK, for the licence fee)? There's also the question of recording a different channel to the one we're watching.

Title: Re: Digital switch over
Post by CWatters on Dec 21^st, 2009, 10:11am

Not all stations are created equal. My understanding is that the BBC put in much of the money to upgrade the transmitters because they have a public service obligation. Other channels don't.

The TV part of the spectrum is very crowded and during change over both Analogue and Digital have to share the available bandwidth. To fit them all in they had to use lower power transmitters and different encoding schemes (64QAM vs 16QAM) for some groups of channels.

Because of the public service obligation BBC channels were allocated the "best" mux. This is Mux 1 (16QAM) which is easier to recieve than say 3,4,5 which are all in mux 2 (64QAM).

Many people in the broadcasting industry thought dual running of digital and analogue would be impossible and it's to be honest it's amazing that it's worked so well.

> we're now seriously considering going the satellite route,
> which I've always resisted on principle - why pay for more
> channels..

Have you consider FreeSat? No subscrption required for that and free HD channels, just needs a box and the dish.

http://www.freesat.co.uk/

Title: Re: Digital switch over
Post by londonman on Dec 21^st, 2009, 5:30pm

Screwfix have a very good cheap dish available for FreeSat.

re recording...Humax FreeSat box - record two channels while playing back something previously recorded.

Title: Re: Digital switch over
Post by Joiner on Dec 21^st, 2009, 6:15pm

Much obliged chaps. It's doing our heads in. >:(

Title: Re: Digital switch over
Post by CWatters on Dec 27^th, 2009, 2:00pm

If you have a lot of hills and trees around google DIY satellite installation to check where the dish would have to go. It needs unobstructed line of site to the south east. Sat reception is usually pretty good except sometimes in really heavy rain or snow.

Title: Re: Digital switch over
Post by Lectrician on Dec 27^th, 2009, 2:05pm

Trees are the main issue with dishes due to hundreds of reflected signals.

Other fixed obstructions are often workable.

A standard sky minidish is 43cm, which has long been classed as too small for free-sat and even sky (it was a sales ploy by sky).

You are best to use a 50cm dish, or ideally a 60cm dish. The larger the dish, the less 'rain fade' you will suffer. 60cm dishes are used as standard up north as the signal is lower due to the footprint. To combat rain fade up north, you need to go larger still.

Title: Re: Digital switch over
Post by Joiner on Dec 29^th, 2009, 1:50pm

When you go on the Freesat site they have the Sagem box on there for £199.99 from Argos. Go onto the Argos site and it's £249.99! :(

Title: Re: Digital switch over
Post by Lectrician on Dec 29^th, 2009, 2:12pm

Humax boxes are the most popular for freesat.

If you want to be able to record, you would be best going for one with an HDD built in, these have a dual tuner (best to double check), and would require two cables from the dish, and a dual LNB at the dish (duals are more expensive than quads these days, so get a quad).

Title: Re: Digital switch over
Post by Joiner on Dec 30^th, 2009, 8:49am

Son-in-law has Sky and the aerial chap (a mate of his) said he could run our system off their dish, but it already has FIVE wires coming out of it because their kids both have freesat. I'm going to insist he fits another dish.

What really pisses me off is that we're forking out £370 for something we shouldn't really need!

Title: Re: Digital switch over
Post by CWatters on Dec 30^th, 2009, 9:19am

I believe you can get an LNB for a sat dish with 8 seperate connections. He may have one already (eg five used with three spare).

Title: Re: Digital switch over
Post by scotspark on Dec 30^th, 2009, 1:51pm

yeah if he has 5 feeds already he must have an octo LNB so 3 free 2 for your freesat then 1 left spare saves having another dish

Title: Re: Digital switch over
Post by Joiner on Dec 30^th, 2009, 3:47pm

Phew!

Title: Re: Digital switch over
Post by Lectrician on Dec 30^th, 2009, 4:20pm

Octo's used to be fairly rare and expensive, but are now fairly common.

They did not used to be available with a mini-dish mount, but do appear to be now.

Once you hit 8, to go above this you need to use a QUATTRO (not quad) LNB and a 'multiswitch', effectively you then have unlimited independant outputs depending on the amount of outputs on the multiswitch, although multiswitches can also be stacked.

Some lower end multiswitches can actually use a quad LNB rather than an expensive quattro, but the budget multiswitches do not have great stats.

Title: Re: Digital switch over
Post by scotspark on Dec 31^st, 2009, 3:14pm

the need for quattro lnbs and multiswitches is rare for domestic

I have fitted a few octos thoi when they put boxes in the bedrooms as well

Title: Re: Digital switch over
Post by Lectrician on Dec 31^st, 2009, 3:26pm

No, QUATTRO and multiswitches are more for flats etc, and can also incorporate terrestrial on the distribution. We have used them in several larger houses and houses with annexes/holiday flats etc.

You need to go for a larger dish (80cm) plus with multiswitch installs as a multiswitch will inherently drop some of the signal, as will the no doubt longer cable runs associated with larger installs. You cannot boost a satellite signal, you need to start off with a nice strong signal before allowing it to 'degrade' down to a useable one.