| Non-motoring > TV aerials | Miscellaneous |
| Thread Author: bathtub tom | Replies: 2 |
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New Mon 22 Aug 22 22:47
TV aerials - bathtub tom
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I live within a couple of dozen miles of Sandy Heath and replaced my UHF aerial with a wideband one some years ago. I can see the top lights of the transmitter from the top of my road and suspect my aerial can 'see' it without obstruction. Moving to a new house a mile away, I thought I'd take my wideband aerial with me (it's in the loft). I tried the reception in my old house on the old UHF aerial, found the signal strength and quality were almost as good as the wideband aerial. I also found they were almost the same on the aerial lead with no aerial connected. I don't undersand this stuff, can anyone enlighten me as to why I bought a wideband aerial? Perhaps I'd been better off spending my money on an Ariel Red Hunter/ Arrow/Leader? |
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New Mon 22 Aug 22 23:21
TV aerials - Zero
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Back in the day of analogue transmitters, aerials were grouped, depending on where on the allotted frequency band the broadcasts were on, so they were tuned to a part of the band. Sometimes the channels used were far apart on the band, so you needed a wideband. These days, with digital, you are receiving a lot of channels interleaved - Multiplexed or mux - on a single frequency - or several frequencies but they tend to be closer together. TBH in the old days, unless you lived in a fringe area, wideband aerials were adequate. Today its not about signal strength but signal quality ( or error correction) |
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New Tue 23 Aug 22 08:45
TV aerials - tyrednemotional
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...you need to understand the history, and a small amount of the technology. Both the historic analogue and current digital TV signals utilise the same frequency range and subset of frequencies, which were originally designated Channels 21 to 69. A given Channel could only contain a single analogue transmission (e.g. BBC1), whereas a digtal transmission on a single channel has multiple content (e.g. BBC1, BBC2, ITV, Radio2, etc. etc.) "multiplexed" together, and decoded and split by your TV. So, say 5 Channels on the old analogue system would give you BBC1, BBC2, ITV, CH4 and CH5. 6 multiplexes ("MUX") on the digital system, the equivalent of 6 Channels and thus utilising very little more frequency bandwidth will give you 100+ TV and Radio services. On analogue, picking up more than one transmission on the same frequency could/would cause interference on picture and sound (e.g. ghosting if it was the same transmission from multiple sources). Hence, adjacent transmitters generally used a completely different subset of frequencies for transmission, these were from a given chunk of the frequency range, and aerials were designed (known as banded aerials) that would favour the local transmission frequencies, and reject those "out of band" thereby largely avoiding the issue. When digital services were introduced, they ran alongside the analogue ones for some time. There was a need to find Channels from the 21 to 69 for digital transmissions, and they couldn't be the Channels already in use locally for analogue , nor those different Channels used by adjacent transmitters (a digital signal would interfere with an analogue one on the same frequency). The solution in many places was to go completely out of (local) band with the digital transmissions (often of necessity across a wide frequency range, and sometimes accompanied by a move and re-tune of the existing analogue services). Since many aerials were "banded", they wouldn't receive any out of band new digital signals, and it was common during the digital rollout for an upgrade to a wideband aerial (capable of receiving everything in the 21-69 range) to be required/recommended for digital reception. As we move forward, analogue transmissions have been ceased, and there has been a move to release some of the TV frequency spectrum (it is now channels 21 to 60). Digital to Digital transmission interference is not a significant problem (due to the differing reception technology), and there has been a move around the Channel numbers and consolidation of many digital transmissions over the last 9 years or so. In your case (Sandy Heath) all digital MUXes bar one are now transmitted in frequencies that are covered by Band A aerials (21-37). If, as is likely, the old analogue transmissions were also Band A (and your old aerial) then it will be appropriate for the great majority of the current digital services. The one that is not in the Band A frequencies is the ARQ B MUX, which carries a number of the minor channels ("Yesterday" would be a good test). You may not receive programmes on this MUX with the old aerial (though if you can see the transmitter, a piece of wet string might be enough). All the mainstream stuff should be absolutely fine. |
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