All posts by Mike Dimmick
Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.
R.Strawson: I would strongly advise against getting an aerial from a high-street retailer or DIY store. They don't know what they're selling. The MZ40T is a 'contract' type: these tend to have very uneven response across the band - the gain on one channel may be very different to that on another, giving strange results.
At your location I would go for a small log-periodic such as the DM Log or Log40 at Online TV FM DAB Aerial sales . You are in a very strong signal area and should have no trouble unless trees block line-of-sight to the transmitter.
If you have a booster, you should remove it. It's very unlikely to be doing anything useful and could easily be overloaded. You may find that you need to use attenuation even with a lower-gain aerial.
I would also check that the cables are in good condition. If they've been up for more than 10 years, replace them. Use 'satellite-grade' cable with copper-braid-over-copper-foil screening, such as Webro type WF100. Ensure that you clip down the cable as it passes over brickwork and tiles - see Satellite, Television, FM, DAB, Aerial, Coaxial Cable, Plugs, Sockets, Connectors & Leads for ensuring it can't move.
Your problem could well be that water has got into the cable, which changes the cable's performance, increasing losses but increasing losses at higher frequencies to a much greater extent than lower ones. Or, the cable run could just be too long - the longer the cable, the more signal is lost, and it's worse at higher frequencies than low ones.
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Brian Barron: howtoreceive only lists analogue, and various internet video sites. It isn't available on Freeview (it would appear on DMOL Pre-DSO Multiplex Channel Allocations if it were on one of the regular multiplexes, and the Manchester local multiplex is listed on DMOL Post-DSO Multiplex Channel Allocations ).
Because it's right up at C62, you're likely to need a wideband aerial, Divis uses mostly Group A except for Mux C on C48. (You also need a wideband for TG4, on C59.)
Ofcom list Restricted Television Service Licensees at Ofcom | Restricted television service licences , where they indicate that a digital service licence may be possible, though probably not until after DSO. One thing's for certain - they won't be staying on C62, that channel is being cleared for 4G mobiles. Now the main UTV-region plans have been published (25 May), it may be possible to plan the new location, although an RT multiplex (carrying at least RT One, RT Two, TV3 and TG4) is due to be fitted in somewhere as well.
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Jane Stevens: Digital UK shows a very high 99-100% probability of reliable reception with a roof-top aerial. A well-sited loft aerial is still quite likely to give good reception.
If you have an amplifier, try it without - you really shouldn't need one at that distance.
If you've just retuned in order to pick up a new channel - I know 'Really' launched recently - your box may have picked up the wrong transmitter, particularly if you retuned in weather conditions that cause signals to travel further than usual.
Otherwise, I'd suspect that something is no longer connected - again, signals could still be strong enough for something to be detected even without the aerial. Check for any breaks in the cable, that the connector on the end is making good contact with the input on the TV or receiver, and that it's securely connected at the aerial.
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Peter: Beardsley Way looks like blocks of flats on the Birds Eye view on Bing Maps, are you using a communal aerial system?
If you are, you may find that your building's owner has used a channelised system, which filters and distributes only the channels that Crystal Palace used before HD was added. It would need to be extended for HD, to include C31 as well as all the others. You may find that they're not willing to do this, given it's now less than a year before the whole thing will need to be reconfigured for switchover.
If you have your own aerial, I can't see what the problem would be, as this is a very strong signal area. See Single Frequency Interference for thoughts on what might be blocking this one frequency.
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P.JONES: Check for 'sharpness' settings in the TV's configuration menu - though usually they come configured with too sharp a setting.
A new TV will usually have a native HD resolution, and have to upscale SD broadcasts, so some blurring is inevitable as the screen resolution is not an exact multiple of the SD picture's resolution. Again, worth seeing what options are available to correct this.
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There's a new list of proposed channel numbers and maps in Ofcom's PDF at http://maps.ofcom.org.uk/….pdf .
Not convinced about using the same channel on two different antennas at Hannington, and three different at Winter Hill!
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Ian: Nottingham is in the East Midlands.
John Robinson: Looks like that paragraph has been written by some political junkie, not someone technical. Very, very careful aerial design and positioning is going to be necessary to avoid co-channel interference on the edges of the petals, between the signal transmitted on each antenna for each sector. Of course they may have taken this into account and not expect any real coverage in the edges of the petals, note that The Wrekin petal A and 2 are on different frequencies.
There is no channel zero, someone forgot to fill it in. Given what they've done elsewhere I assume it will be C56 as on the other two petals from Winter Hill.
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Briantist: True, but that's confusing UHF channels with Logical Channel Numbers. The document clearly means UHF channel numbers.
Ian: MATV is still licensed in Leicester under a Restricted Television Service Licence, though there are reports that it has now shut down. It's possible that they will be offered a chance to bid for an interleaved frequency, as an existing RTSL for Leicester.
If it is still running, it would be broadcasting on C68 from a mobile phone tower near Ratcliffe College - mb21 - The Transmission Gallery .
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Damian: With the correct aerial, pointed in the correct direction. Check Digital UK's postcode checker to avoid disappointment.
Note that Stockland Hill's commercial multiplexes remain on low power until after London's DSO on 18 April 2012, so you might not be able to get it now, but might be able to after that.
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Tuesday 9 August 2011 1:58PM
Gaetan: It appears that the radiation pattern of the new main antenna at the Oxford transmitter is a bit different from the old one, and this could have had an effect on your reception. I believe it is actually more circular than before, and also the old aerial did not actually allow the ERP of 500kW to be reached, which means you could well be getting more signal than originally intended.
If you're using a booster, remove it. If not, try adding an attenuator. If neither of these helps, complain to the property management company - the Master Antenna TV system should be adjusted so that levels on all channels (analogue and each digital multiplex) are within acceptable ranges at each socket provided.
Do other residents in the building have the same problem? If so, that would definitely point to a problem with the system. Do ensure that you keep your mobile phone well away from any TV aerial cables, whether visible or likely locations for them to be buried in the walls, because GSM phone frequencies are very close to the top of the TV band, where Mux 2 lives.
The management company should definitely be arranging for the system to be adjusted on 14 and 28 September, as the levels required for BBC A are going to be quite different from those for Channel 4 analogue (which the high-power BBC A multiplex replaces on C53), and the commercial multiplexes will use frequencies never before used at Oxford.
If the system is not adjusted you may well end up with too much signal after switchover, and/or be unable to get the commercial multiplexes at all, depending on how the MATV system is constructed.
For general advice on communal TV systems, see PARAS - Professional Aerial Riggers Against The Sharks .
The actual prediction at your location is for 99-100% probability of reliable reception, on all multiplexes, both now and after switchover, so unless there are issues not covered by the predictor - trees or large buildings nearby - there is some problem with the system. There are a few large trees there, but it should have been possible to site the aerial somewhere that they wouldn't block the path to the transmitter.