View Full Version : Aerial help for Terrestrial DTV please...
Hi all,
As noticed mentioned in another post, I am also a Telewest customer but have bought a little freeview usb adaptor to get freeview on my PC. Thing is I'm having trouble with the reception.
The nearest transmitter is...1km away!
It apparently provides all DTV channels available and www.dtg.org.uk (http://www.dtg.org.uk) says that I need a C/D vertical aerial? Thing is I can't find out anywhere what exactly one of those is? Is my closeness going to be an issue, i.e. need an attenuator or something?
My house already had a sky dish on the back when I bought it as well as practically the biggest most obvious aerial in the neighbourhood! I bought a sky box for a fiver which can get free satellite channels (stuff like Zone Horror for example) and the freeview thing can get Sky Three until Telewest gets it (having nagged them about Sky Two and Three recently to a very confident advisor who knew in depth about their agreements with Sky etc. Great to have a knowledgeable advisor!)
---------- Post added at 17:52 ---------- Previous post was at 17:07 ----------
Quick follow on to this...
I tried connecting the cable from my big roof aerial to the usb adaptor and it showed good signal but didn't find any channels...
I take it from that the aerial isn't compatible with digital?
All TV transmitters in the UK operate within certain sections of the available UHF spectrum. The sections are assigned to transmitters in such a way that no transmitter interferes with the broadcasts from any of its neighbouring transmitters. The chunk of the UHF spectrum assigned to any given transmitter is denoted by a letter. When buying a TV aerial, you need to know the code letter of your local transmitter, and then when you go to the TV shop, buy an aerial with a matching letter. Aerials - large, rooftop ones, certainly - have a colour-coded plastic bung in their nose that corresponds to their code letter.
Frequency group C/D broadcasts on UHF channels 48-68 and the appropriate aerial's colour code is green. Full details here: http://www.bbc.co.uk/reception/factsheets/text/tv_aerials_factsheet.html
Digital and analogue transmissions from the same transmitter may be broadcast from different frequency groups - hence the usual advice, if you want to receive both analogue and digital signals from the same aerial, is to get a 'wideband' aerial, that receives signals across all channels (21-68, code letter W, colour black). However there would be no point getting a wideband aerial for a digital-only USB receiver, so follow its advice and go get yourself a C/D aerial. Any high street stockist will understand what you're asking for, as would any online retailer.
If you want to doube-check what channel group your rooftop aerial is receiving, without going on your roof and peering at the end of it, go to the Wolfbane analogue transmitter database here:
http://www.wolfbane.com/cgi-bin/tva.exe?
Put in your postcode and it will tell you what your local transmitter is, where it is, and what its analogue channel group is. There is also a digital database here if you're interested:
http://www.wolfbane.com/cgi-bin/tvd.exe? (http://www.wolfbane.com/cgi-bin/tva.exe?)
---------- Post added at 18:28 ---------- Previous post was at 18:17 ----------
Edit
Horizontal / Vertical simply denotes which way you hang it on your wall - with the metal bars lying horizontally or vertically. Normally, any aerial you buy will be able to hang either way up. This information is mainly to help you erect rather than buy it.
Main transmitters are polarized to emit vertical waves, smaller local fill-in transmitters emit horizontally, so you position your aerial to match.
Excellent, really helpful stuff, Cheers Chris :o)
Just popped out to have a look at my aerial. I couldn't see anything coloured on it though. There's the circular bit where the coaxial cable comes out but that's grey. Bit difficult to see properly as it's too dark at the moment...
I'll have another look tomorrow
Just had a look at those two links, the aerial suggestion is a set-top for both as my transmitter is 1 mile away at 117 degrees. My aerial is attached vertically.
All TV transmitters in the UK operate within certain sections of the available UHF spectrum. The sections are assigned to transmitters in such a way that no transmitter interferes with the broadcasts from any of its neighbouring transmitters. The chunk of the UHF spectrum assigned to any given transmitter is denoted by a letter. When buying a TV aerial, you need to know the code letter of your local transmitter, and then when you go to the TV shop, buy an aerial with a matching letter. Aerials - large, rooftop ones, certainly - have a colour-coded plastic bung in their nose that corresponds to their code letter.
Frequency group C/D broadcasts on UHF channels 48-68 and the appropriate aerial's colour code is green. Full details here: http://www.bbc.co.uk/reception/factsheets/text/tv_aerials_factsheet.html
Digital and analogue transmissions from the same transmitter may be broadcast from different frequency groups - hence the usual advice, if you want to receive both analogue and digital signals from the same aerial, is to get a 'wideband' aerial, that receives signals across all channels (21-68, code letter W, colour black). However there would be no point getting a wideband aerial for a digital-only USB receiver, so follow its advice and go get yourself a C/D aerial. Any high street stockist will understand what you're asking for, as would any online retailer.
If you want to doube-check what channel group your rooftop aerial is receiving, without going on your roof and peering at the end of it, go to the Wolfbane analogue transmitter database here:
http://www.wolfbane.com/cgi-bin/tva.exe?
Put in your postcode and it will tell you what your local transmitter is, where it is, and what its analogue channel group is. There is also a digital database here if you're interested:
http://www.wolfbane.com/cgi-bin/tvd.exe? (http://www.wolfbane.com/cgi-bin/tva.exe?)
---------- Post added at 18:28 ---------- Previous post was at 18:17 ----------
Edit
Horizontal / Vertical simply denotes which way you hang it on your wall - with the metal bars lying horizontally or vertically. Normally, any aerial you buy will be able to hang either way up. This information is mainly to help you erect rather than buy it.
Main transmitters are polarized to emit vertical waves, smaller local fill-in transmitters emit horizontally, so you position your aerial to match.
Wrong way round Chris. Aerials to main transmitters have the bars horizontally, the relays are V-pol.
Wrong way round Chris. Aerials to main transmitters have the bars horizontally, the relays are V-pol.
D'oh!
tvout said:Quick follow on to this...
I tried connecting the cable from my big roof aerial to the usb adaptor and it showed good signal but didn't find any channels...
I take it from that the aerial isn't compatible with digital?
i just went out and got a cheapo £12 external Yagi arial and stuffed it inside the loft,works fine, but may stick it outside at some point as a few stations have a little pixelation from time to time as the weather changes.
whats the brand & product no., or rather does it have a BDA driver as standard?. link?
if its supplyed with a BDA driver (or you can find a driver for it that is)then you can use many apps
to run it with, look in its driver section and see if it mentions BDA.
as for the 1 mile or even the 1km away then thats a good thing for DVB-T reception.
when you said "it showed good signal" what do you mean by this if you couldnt lock onto a station?.
rather than retype all my advice again read pauls thread (dont know if he just gave up in the end lol)
assuming a BDA driver:
the simplest DVB-T tuner/app to try first is probably this one
http://www.dsp-worx.de/?n=11
http://www.cableforum.co.uk/board/showthread.php?t=48164&highlight=bda+driver
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