menuMENU    UK Free TV logo Archive (2002-)

 

 

Click to see updates

All posts by Mike Dimmick

Below are all of Mike Dimmick's postings, with the most recent are at the bottom of the page.


Vin Richley: The BBC hope that by the end of 2012, new encoders will allow them to squeeze five channels into one multiplex - currently, they carry four channels. I believe they have to offer Channel 5 first refusal on this space.

As the HD multiplex carries Public Service Broadcasting channels, it will be available on all transmitters, including Fenham and Newton. It's called BBCB above.

Fenham currently carries all six multiplexes and will continue to do so after switchover. Newton will be a 'Freeview Light' transmitter carrying only three multiplexes, as the commercial multiplex operators have refused the option to extend their coverage to the relays. The coverage areas of the main transmitters are generally increasing, so it may be possible to get the commercial multiplexes from one of the main transmitters after switchover.

link to this comment
GB

Kieran R: Sorry, for some reason you had a Southend-on-Sea postcode against your post which I assumed was correct.

If you're using Crystal Palace it's even more likely that the fault is somewhere at your end. Black-and-white and fuzzy/snowy indicates low signal levels or high noise levels. Black-and-white, but clear, suggests a problem with your TV. Check the Colour control!

Digital UK's predictor shows that for you, reception from Crystal Palace will be highly variable now, and up to switchover. While the PSB multiplexes are expected to work reasonably well after switchover, the COM multiplexes probably won't - it shows no prediction, because the same channels are used for the commercial multiplexes from Rowridge.

If you just moved your aerial, rather than changing it, it probably won't work very well. Hannington requires a Group E aerial designed to cover channels 35 to 68, while Crystal Palace requires a Group A aerial designed to cover channels 21 to 38. Wideband and semi-wideband aerials like the Group E type are a compromise, and they're particularly poor at lower frequencies compared to a similar-sized aerial designed for the job.

The analogue signals have to be switched off to make digital TV available to the vast majority of the population, and much more reliable for most of the people who have it now. There just isn't space in the UHF TV band for high power digital at all sites alongside analogue on their current frequencies. The Government also wants to sell off a part of the band for other services.

If you really can't avoid the trees, you will have to consider satellite or cable.

link to this comment
GB

Tony: There were no planned power reductions during the last week.

As I understand it, the engineers work to ordinary working hours and if work is required on the mast itself (rather than the transmitter equipment at ground level) it must be carried out during daylight. The exceptions seem to be power testing and the actual switchover itself which are carried out between midnight and 6am.

Problems experienced in evenings and after dark are more usually to do with the changes in how signals reflect off different layers in the atmosphere, as they cool off. On clear nights, there can be an 'inversion', cool layers nearer the ground which cause signals to reflect. This is termed 'tropospheric enhancement'. For more information see http://www.dxinfocentre.com/propagation/tr-modes.htm. (That site is written from the perspective of *wanting* distant transmissions - here, you don't want them because they cause interference.)

Hook is in the sector of Hannington's analogue coverage area that is not intended to be covered by its digital transmissions. Hannington's current low power digital transmissions use the same frequencies as the Guildford transmitter's analogue transmissions which - until switchover - take priority. Digital UK show no prediction for your postcode. It is not expected to work with any reliability at present.

The aim is for post-switchover digital transmissions to cover the same area as pre-switchover analogue transmissions, and Hannington should give you a good service from the middle of next year. If you can't wait that long, consider using Crystal Palace, satellite, or cable. (RG47SH)

link to this comment
GB
M
Emley Moor (Kirklees, England) transmitter
Monday 28 March 2011 5:14PM
Reading

Mr J Moxon: Virtually all existing transmitters will be converted to broadcast digital signals at switchover. A very small number are closing or moving.

Your only option will be the Cop Hill relay, and you're expected to get excellent results. Cop Hill will be a 'Freeview Light' transmitter, broadcasting only the three public service multiplexes. Channel 5 will be carried on the ITV/C4 multiplex.

For more information, see the Cop Hill transmitter page.

link to this comment
GB

Nathalie Daily: Digital UK currently predict that your reception of signals from Angus is expected to be poor. That is, it won't work reliably. This is expected to improve some time next year (it just says 2012). It isn't clear what's causing the problem - it's likely to be a distant transmitter using the same frequencies that will switch next year, though I can't see an obvious clash.

You might get better results from the Tay Bridge relay, but it only transmits the three public service multiplexes, rather than all six.

It shows that you might currently get a better service from the Craigkelly transmitter, but that this will actually get worse after switchover.

It is only a prediction, and the real situation is more complex than the computer model shows. A local installer may be able to provide more advice.

link to this comment
GB

Andy Maltby: I think there's a reasonable chance that any problems you're currently having are caused by too much signal rather than too little. I've plugged the numbers into Megalithia's Field Strength Calculator, which suggests that with a 10dBd aerial and 10m of downlead, you could be getting up to 78-80 dBuV of signal on the digital multiplexes, and well over 100 dBuV on analogue. The recommended levels are 45-65 dBuV for digital (some say 45-60) and 60-80 dBuV for analogue.

Field Strength Calculator - you're 13.7km away.

At switchover, the PSB multiplexes could be up to 92-93 dBuV. Past switchovers, e.g. Mendip, have shown that high digital signal levels cause more problems than the old analogue signal levels did. You may experience more problems after switchover than you had before.

If you have any amplifiers, you should remove them. You will probably need to add an attenuator to bring the levels into spec. (RG47SH)

link to this comment
GB

Gary Plant: Can you provide a full postcode, so we can see what the prediction at your address is? Radio signal levels can change dramatically with just a few centimetres in either direction, so we do need to narrow it down to a very small area. Small changes in elevation can also change whether you get a clear line of sight to the transmitter or not.

As far as the transmitter information goes, this website only republishes the information from Digital UK's Planned Engineering Works page at
Digital UK - Planned Engineering Works
.

In general, all the main transmitters are getting an overhaul and this is happening region-by-region in roughly the order that the transmitters will switch over. As Tyne Tees is the last of the English regions to switch, the transmitter work is only just starting here. At most sites, the main transmitting aerial is being replaced. Depending on whether it had spare capacity, and whether it was allowed to transmit in all directions, sometimes the digital signals were transmitted from the main aerial, or some of them were, sometimes in combination with another aerial.

At Bilsdale, the quoted antenna height (which is an average of all aerials providing the service) for the digital services is a couple of metres higher than the quoted analogue height. This suggests that there are some aerial panels for digital used in conjunction with the main aerial, sat on top of it. Those have to come off to replace the main aerial, so they either have, or are going to, fit a reserve aerial further down the mast to serve as the temporary main aerial. Once this is installed and feeder cables connected, services will move to this reserve aerial, and they will replace the main aerial.

At some sites the FM radio transmission aerials have been immediately below the TV aerials, and the reserve has had to be fitted quite low down. That can cause problems for some people if the terrain prevents a clear line of sight to the reserve aerial.

Generally they are not constructing new buildings for the new high-power transmitters (generating the signal and amplifying it to full power happens at ground level). Instead they are clearing either the existing analogue transmitter halls or the existing low-power digital buildings, if any. Signals may need to be generated by temporary transmitters while that happens, and in some cases they may not be able to produce the full power of the permanent transmitters.

There may be periods of low power when men are working on the mast, or when services are being moved from one aerial to another, or one rack of ground-level transmitter equipment to another. These events will normally occur during daylight hours on weekdays.

Unfortunately Digital UK seem to feel that this information is too technical for the general public, and limit their information to 'possible weak signal' and 'liable to interruption'. (RG47SH)

link to this comment
GB
M
Upgrading from Sky+HD to Freesat+HD | Freesat
Monday 28 March 2011 7:08PM
Reading

Mr S M Davies: I don't have a Freesat box, but I do have a Humax PVR-9200T Freeview+ recorder. If you pause a programme, then later hit record, it will record from the point in the programme that you paused it, which I think is what you mean by 'will record from the buffer'. If you want to keep the whole programme I seem to recall you have to rewind to the beginning, but it's been a while since I've tried it.

The Foxsat-HDR manual does not say that this is possible, but it does not say that it is not. The PVR-9200T manual says that it starts recording from the time you press record, rather than the time on the bar, but this is definitely no longer true!

link to this comment
GB
M
DDR changes for Luton and Dallington Park
Tuesday 29 March 2011 1:20PM

Brian: there are a number of other changes indicated in Ofcom's document at http://licensing.ofcom.org.uk/binaries/tv/sup_dso/version2.pdf. For example, at Andoversford BBC A will start up on C62 and move to C50 at DSO2.

Unfortunately because this is a wide Excel workbook exported as portrait PDF, the notes are truncated, so I don't know what's happening at Lark Stoke between 23 March and 6 April. Would be useful to know! (RG47SH)

link to this comment
GB

Syd Wall: On 6 April, the existing Multiplex 1 closes, as does BBC Two analogue. The new BBC A multiplex (PSB1) starts up on C26, replacing BBC Two analogue. Multiplex B will move to C21 for the two-week period between DSO1 and DSO2.

BBC One, BBC Two, BBC Three, CBBC, BBC News and the other services currently on Multiplex 1 will stop working unless you retune. You will also lose the services on Multiplex B although all the BBC services will be duplicated on BBC A, which is their permanent home. (Sky Sports' permanent home is on the ArqB multiplex.)

Then, on 20th April, Multiplex 2 and B will close, along with BBC One, ITV and Channel 4 analogue. D3+4 starts up on C23 and BBC B (HD channels) starts up on C30. Multiplex A continues unchanged. Multiplexes C and D change to their final mode, becoming ArqA and ArqB, but for now stay at their current power level and channel.

Services will be off-air until 6am on the DSO days. You should retune after that time.

COM/NEW/PSB: There are six multiplexes. Ofcom classifies them as Public Service Broadcasting (PSB), multiplexes operated by the public service broadcasters: the BBC, ITV and Channel 4, and Commercial (COM), operated by SDN Limited and Arqiva Services Limited (two multiplexes). NEW are potential new multiplexes that could be licensed in future: see the Interleaved Spectrum page, although the actual allocations are speculative at this stage and in my view shouldn't be shown here, because they're just confusing.

The multiplexes are also called by the name of the license holder: PSB1 is BBC A, PSB2 is Digital 3 & 4 (D3&4 or D3+4), PSB3 is BBC B or HD (reflecting its use), COM4 is SDN, COM5 is Arqiva A or ArqA, and COM6 is Arqiva B (ArqB).

This webpage ought to be consistent and refer to BBC A rather than PSB1, etc.

Before switchover they were known by numbers and letters, the original PSB multiplexes getting numbers (1 for BBC, 2 for ITV and C4) and the original commercial multiplexes getting letters (A for SDN, B for BBC Free To View Ltd, C for Arqiva A, D for Arqiva B). The BBC has B because originally onDigital/ITV Digital had B, C and D and they were reauctioned when ITV Digital went bust. Ofcom has basically stolen Multiplex B back from the BBC for HD services.

link to this comment
GB