All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Richard Harrison: Does your booster have a variable amplification control on it? If so, then it wants turning down.
Attentuation is the opposite of amplication. So if you decide to keep the booster, and you (for example) put -6dB attenuators on each output, then that is the same as reducing its amplification level by 6dB (assuming that the device allows reduction of its level).
What I would do (and I remind you I'm not a professional) is do some experimentation. Remove the booster and connect the aerial straight through to one of the outlets. The one with the longest cable would be the best as it is going to be the one with the least signal. You could try doing the same to others and see what you get.
If the TV still shows 100% strength, then you can be pretty sure that the -8dB attentuation will not put it below what the TV needs to work.
I say this because I have 90% strength from my loft aerial (at 25 miles from Emley Moor) and when I insert my variable attenuator and turn it to max attenuation (-20dB), all muxes are still receivable (strength 40-odd percent). So I know that with my 10m of WF100 coax, the signal level is still at least 20dB over what the TV needs to start to work.
More info on splitters here:
Television Aerial Boosters / Amplifiers, Splitters, Diplexers & Triplexers
Also see the page on cable types:
Satellite, Television, FM, DAB, Aerial, Coaxial Cable, Plugs, Sockets, Connectors & Leads (DN31NJ)
| link to this comment |
Aaron: I suggest that you stop using the booster for a start off. Read this page:
Freeview signals: too much of a good thing is bad for you | ukfree.tv - independent free digital TV advice
Get yourself a variable attentuator from eBay.
Tune the devices in using the loft aerial as it's known to work. Then take them to the rooftop aerial.
Bear in mind that, as explained on that page, that receivers that indicate "no signal" or "low signal" could in fact be being fed too much signal which effectively blinds them. (DN31NJ)
| link to this comment |
The thing to note about Sudbury is that it actually consists of two masts, as shown:
The Big Tower Sudbury Transmitter
mb21 - The Transmission Gallery
MB21 explains that Sudbury B mast (the shorter one) was built in 1997 to facilitate broadcast of digital TV. It says that the signal is not omnidirectional. That is, it doesn't throw out as much signal in all directions (where as the main Sudbury mast does). It is to the south east of the mast where the signal isn't as strong.
At switchover, the main mast (that previously broadcast analogue) became the transmitter for the digital PSB muxes. The COMs remained on Sudbury B:
Sudbury Transmitter
How this may be of relevance here, I'm unsure. Perhaps those who could pick up ArqB prior to the other day were on the fringe and a slight change of frequency has pushed them over the edge.
It has occured to me that they might have switched antenna for ArqB from Sudbury B top array to the one which broadcast Mux 2 (pre-DSO) which is below the others, but what can clearly be seen in some of those photographs (see ATV and mb21 links) as having a gap in one face (I can't make out which direction it is though). I would be surprised if they would have done this simply because this would obviously leave some without a signal who had it post-DSO. The question is, is this what has happened? (DN31NJ)
| link to this comment |
Sudbury Arqiva multiplex B changes 16 November - retune require
Thursday 17 November 2011 11:39AM
Doncaster
Thursday 17 November 2011 11:39AM
Doncaster
yes: The plan is to move the COM muxes to the main mast as well (this will happen in June).
| link to this comment |
Chrissy: Don't expect sparkling results; a rooftop aerial is generally best. Conversely, a low indoor aerial is not going to work as well.
That said, if you are going to try, then if you have a fixed aerial (or one you know works), take the new receiver to it and tune it in.
The issue you've got (I think you've worked this out) is that in order to tune the device you need an aerial that picks up the signal and in order to put the aerial in a suitable position to receive the signal you need your receiver tuned in. It's catch 22 (as there are two unknowns, as it were).
That is why I would always tune with an aerial known to be good (fixed/rooftop preferred).
Once your receiver is tuned, look where to site your aerial. You might need an extension if it works best on a high shelf, for example.
It needs pointing in the direction of Crystal Palace, which is west from your location (see the direction neighbours' aerials for a clue).
You need to site it where the signal is best. The more walls it has to go through, the weaker it will be. Ideally it wants to be at the side of the house that faces the transmitter, although neighbouring buildings will cause a shadow (thus weaker signal), which is why I said not to expect sparkling results.
As your area hasn't switched over to digital yet, it is probably easiest to tune with an analogue TV and analogue pictures act much more of a gauge as to where the signal is warmest in the room. You might find one general area of the room where signal is the best. That gives you a general idea of where your aerial will work best.
One final thing, be mindful that having the booster turned up full doesn't necessarily mean that you will be more likely to get the best signal (better than if it was lower).
| link to this comment |
David Meadows: Digital UK Tradeview coverage predictor and Ofcom info says it is C29.
If you have a booster? If so, try removing it.
| link to this comment |
Kevin Hodges: You're not alone!
See:
Sudbury Arqiva multiplex B changes 16 November - retune required | ukfree.tv - independent free digital TV advice
What I would do if I were you is either take the STB that doesn't find the channel to an aerial outlet that has been used to successfully tune in another receiver.
You could even try taking the 'working' STB or TV to the aerial socket where the one that won't pick it up.
Not all tuners are as sensitive as one another. If the cable from the amplifier to the wall socket is longer for one, then more signal will be lost along its length.
If the booster has a variable control on it, you might be able to adjust it. (DN31NJ)
| link to this comment |
Paul: I have assumed the model number to start "GD" instead of "GB" and I've found the instructions for it here:
http://www.thesupportsite….pdf
The issue would appear to be caused by the receiver picking up more than one transmitter's signal.
I note that page 23 of the manual says that it will ask you for your "preferred region". Perhaps the problem would be fixed by selecting an alternative region (are there multiple regions on the list?) as each entry on that list probably pertains to a different transmitter.
I suspect that you're aerial is on Sutton Coldfield. Based on the Digital UK predictor, Lark Stone also probably comes in quite strong in your area. The PSB muxes (BBC/ITV/C4/C5/HD) from Lark Stone are on lower frequencies than that of all those from Sutton Coldfield.
It might be worth carrying out the procedure at the top of this page and then starting another scan, again with the aerial unplugged, but plugging it in when progress gets to 25%. (DN31NJ)
| link to this comment |
Faye: Try re-plugging your SCART lead. Or try swapping it end to end.
Turn down the sound first though!
| link to this comment |
Wednesday 16 November 2011 2:06PM
Richard Harrison: See this site's explanation:
Usage and abusage of DTT TV booster amplifiers
It is possible that there will be too much signal going into your booster. So the problem isn't necessarily too much signal into your TV; it could be one or the other or both.
*Perhaps* you could remove it all together and replace with a four way splitter:
Online TV Splitters, Amps & Diplexers sales
As you can see, there is 8dB attentuation on each output when a 4-way is used.
Whether you can do away with the powered amplified obviously depends on the signal level from your aerial.
Bear in mind that there will be a certain amount of loss in the cables, so the longer they are, the more attenuation they give.
As a non-professional myself, I suggest that you have a look at the information on www.aerialsandtv.com (DN31NJ)