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| Can I receive Freeview? Get a free report by clicking HERE. When you have a Freeview reception problem, the first thing to do is to look here: http://www.bbc.co.uk/reception/transmitters/ If there's no mention of transmitter work then a lower than usual transmitted signal is unlikely. When you have a problem the LAST thing you should do is "rescan channels". The reason is simple. If, for whatever reason, your receiver is not seeing full signal strength for one or more multiplexes, then rescanning is likely to lose it altogether. What you ought to do is to check everything, starting with the "fly-lead". 1. Replace all fly-leads with decent ones. (Not the cheap Hardware Store "clothes line" type.) For DIY see this page: 2. Check behind wall plate(s) for bad connections. It's not uncommon for wires to snap. It happened to me. (People ask me "but if the wire's broken, how come some channels are OK?" Well, RF signals can jump small gaps. It manages to jump the gap between the transmitter and your aerial!) 3. If the system uses an amplifier, make sure it's still receiving power. The power supply is often plugged in downstairs. Check all plug connections. Where they have to pass power to an amplifier, they should be soldered or crimped. 4. If the aerial is in the loft, make sure it hasn't been moved and nothing has fallen on it. 5. Test your receiver at a nearby house or buy/borrow another (cheap) one and try it. 6. If the aerial is inaccessible to you, get a professional to check it. Replace it and the cable as necessary. Use satellite TV cable which is double-screened copper-on-copper. Ordinary "aerial cable" is greatly inferior and will inevitably give problems with digital signals. The cable should preferably be one continuous run, since connectors and wall plates can cause "signal reflections", resulting in loss or poor performance of some channels. This effect can also be caused by kinks or water in the cable! How? Many aerial fitters don't secure the cable. I've seen lots of cases where the cable was simply thrown over the roof and left to flap in the wind - with inevitable results. The outer PVC sheath wears away on the tiles and rainwater gets in. If you are lucky, the water won't have reached your receiver - yet! In addition, they don't waterproof the aerial connections. I recommend pressing some nice gooey "Blu-Tack" over the cable terminations on the aerial before fitting the plastic rain cover. Make sure that no moisture can enter the end of the cable. Keep the aerial and cable away from traffic. Keep the cable away from mains power cables. Digital terrestrial signals from the aerial are extremely weak and are very susceptible to electrical "noise" generated by motor vehicles, trains, thermostats, kettles, light switches, dimmers, etc. This can cause momentary picture "freeze" which is most undesirable. If interference is getting in to the cable and you can't replace it with fully-screened cable, fit an aerial amplifier as close to the aerial as you can get (the loft may do if the aerial is immediately above). At the lower end of the cable, you can then fit an attenuator, which will help reduce unwanted electrical noise. Satellite TV cable like WC100, H109, CT100 attenuates the aerial signal at 600 MHz by approximately 0.15dB per metre. So a 20 metre run of cable will lose 3dB (= half the signal available at the aerial). You can compensate by fitting a 3dB amplifier near the aerial. Better still, fit a 9dB amplifier at the aerial and a 6dB attenuator at the receiver. This means that the receiver will see exactly the same amount of signal as received by the aerial but any interference picked up by the cable will be reduced by at least 6dB. |
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| Will a booster help? Probably not. Read the technical explanation here.
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| What is a "mux"? "Mux" is short for "multiplex". A multiplex is equivalent to a single channel frequency which, due to the wonders of digital compression, carries several programmes "multiplexed" together. The job of a Freeview receiver is to tune to that multiplex frequency then unmix a single programme from the mux. See http://www.ukfree.tv/txdetail.php?a=NS828647 You'll see the 6 multiplexes listed for the Black Hill transmitter near Glasgow, together with the number of the UHF channel that each one uses (from 21 to 68). | |
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| What is Ariel? It's a brand name for washing powder. (OK, it's also a brand of motorbike and a deer-like animal). |
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| What is Arial It's a computer typeface (font). | |
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| What is an aerial? It's a bunch of metal sticks. What is a "digital aerial"? There's no such thing! |
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| Typical question: My location is at CM6 3HT Answer: Use the Wolfbane site: http://www.wolfbane.com/cgi-bin/tvd.exe? Type in your postcode and click GO. Select your desired transmitter and note down the "Field" value in dBuV. Call this value "D". Note down the letter under "Gp". This is your aerial group. Then http://www.wolfbane.com/cgi-bin/tva.exe? From the top table note down the "Field" value in dBuV. Call this value "A". Measure the approximate length of cable required in metres (from aerial to Freeview receiver). Multiply it by 0.2. Call this value "L". 75 + L - A = your maximum aerial gain. 50 + L - D = your minimum aerial gain. Now you should aim to get your aerial gain somewhere near the middle. Suppose it works out as 9dB min and 16dB max, you need an aerial gain of about 12dB. This is typical of an ordinary aerial. If it works out as 20db min and 22dB max, then you might need a 16dB aerial (massive) with a masthead amplifier to make up the difference (21 - 16 = 5dB). Explanation: A typical Freeview receiver needs at least 50dBuV of signal to work reliably. But at 80dBuV it will be swamped. (But the signal goes up after dusk so I reduce the safe limit to 75). The analogue signal is usually stronger than the digital so we must make sure that the analogue signal is below 80 and the Freeview is above 50 (not forgetting to take into account the losses in the cable). Full discussion here: http://www.avforums.com/forums/showthread.php?t=480832 More here: http://www.avforums.com/forums/showthread.php?t=472874 And here: http://p206.ezboard.com/fsatcureforumfrm9.showMessage?topicID=181.topic Some really useful info HERE. | |
Sam's Black Museum | |
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| This type of flimsy "Yagi" aerial might be OK in a loft but you are asking for trouble if you mount it outside. You'll notice that a fat pigeon has jumped on it and knocked off the top reflector element. It won't be long before the rest come off. In addition, the cable isn't routed tidily and secured with cable-ties. The pole's diameter is too small. It should be at least 1.5" diameter for this size of aerial. |
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| The dish is nicely mounted on a large bracket and a 1.5" diameter pole which is bolted to the brick wall. But some twit has mounted an aerial on a flimsy loft bracket and screwed it to the wood fascia panel. You'll notice that the aerial is pointing at the ground and the cable has never been secured properly. |
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| Another cowboy job! Someone has mounted two aerials on a flimsy 1" diameter tube. The flimsy bracket is falling off the wood fascia panel. The cables are simply hanging down and draped across the tiles. |
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| Two aerials are mounted so close together that they can't possibly work without interfering with each other's signal. And why use TWO aerials pointing at the same transmitter? One is a high-gain and one is a low-gain contract aerial. Has the installer never heard of masthead amplifier/splitters? |
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| This large X-beam aerial has been stuck on a 1 inch diameter tube and nailed to the fascia board - with inevitable results. |
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| It's obvious to you and me that the brackets aren't far enough apart. They should be a minimum of 1/5 of the mast length apart. In addition, the cable has simply been thrown down the roof. Another cowboy earns his spurs.
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