All posts by Dave Lindsay
Below are all of Dave Lindsay's postings, with the most recent are at the bottom of the page.
Brian Aldridge: The above explanation does not say that the News channels are moving on 17th October. They will move when "General Entertainment" reaches greater capacity:
"The Children's and News channel numbers will move on the Wednesday that follows 16 weeks after LCN 65 is allocated (ie when the General Entertainment genre nears full capacity). In the event that the move date falls during a change freeze then the move would take effect on the Wednesday that follows the end of the change freeze."
| link to this comment |
Michael: All transmitters broadcast the HD services as these are carried on one of the PSB (Public Service) multiplexes. It is the COM (Commercial) multiplexes which have less coverage due to them not being carried by small relays such as Weymouth and because there are locations where they can't be picked up from the 81 transmitters that do carry them but where the PSBs (from the same transmitters) can be.
It is worth having a look around your area to see where others are receiving from this might yield some clues, although be mindful that it doesn't necessarily mean that COM channels are available (see explanation below).
The reason being that the COM channels often use UHF channels (frequencies) that are re-used in closer proximity than the those used by the PSBs. In the case of Stockland Hill's COMs, they are co-channel (same UHF channels) as Rowridge's COMs. The PSBs from these transmitters aren't co-channel though. As a result, so as to reduce or avoid interference the transmission powers of the COM transmitters aren't as great as those of the PSBs. Consequently, some fringe viewers will find that COMs are intermittant or unavailable. Clearly you aren't in a great coverage area, so you "may" potentially find that you can receive Stockland's PSBs, but not COMs which would obviously make you no better off than you are now.
Stockland's PSBs are at 50kW horizontally and Rowridge's PSBs are 200kW horizontally and vertically (Rowridge is a unique main station in that it broadcasts using mixed polarity). But Stockland's COMs are 25kW and Rowridge's are 50kW horizontally and 200kW vertically.
Whether you get interference from Rowridge's COMs and/or whether you suffer due to the lower power Stockland COMs is obviously really only something that can be determined by an installer on-site. These are potential issues I am making you aware of.
The Digital UK Postcode Checker "thinks" that reception of the PSBs from Rowridge (horizontally and vertically) and Stockland's PSBs are "good", but "thinks" no reception for both transmitter's COMs. Unfortunately we don't know on what basis it considers this. It could be that lack of reception of Stockland's COMs is purely because of the predicted interference from Rowridge. So in practice "if" it isn't an issue for you (i.e. somehow you happen to be screened from Rowridge more than the predictor "thinks"), then perhaps you will have a better chance of reception from Stockland.
Prediction of the propagation of RF signals is very rough and therefore the Predictor should be used as a guide and taken with a pinch of salt. Measurement on-site is the only real way of knowing what can be received.
All Stockland Hill's UHF channels are in Group A, and therefore a wideband aerial isn't necessary. Wideband yagis have much less gain on Group A channels, so only use a Group A yagi aerial (if you use a yagi).
See ATV's site for information and products:
Digital TV Transmitters Nationwide Page 2
Rowridge Transmitter
Failing that, I wonder what the likelihood of reception of Rowridge's COMs is (vertically, of course)...
| link to this comment |
Briantist: Thanks.
So Freeview HD (PSB3 mux) uses DVB-T2 with 256QAM. Is the reason that the NIMM is much more robust (and can therefore carry further with much less ERP) because it uses 16QAM?
| link to this comment |
John: The principle of a receiver tuning to a neighbouring transmitter existed in the days of analogue as well.
No tuner will ever be totally infallible to this. However, it is really down to the tuner's design as to whether it tunes to the first signals it finds or some other method that is particularly prone to choosing the "wrong" signals.
It is the case that the design of some receivers leave a lot to be desired. They have evidently only ever been tested in a lab when presented with signals from one transmitter. Every receiver should offer manual tuning which is particularly useful in situations where automatic tuning doesn't produce the correct result.
You blame Freeview yet it is your aerial system which is picking up the Welsh signals. I am not sure what you think Freeview should do put up an iron curtain between England and Wales to ensure that RF signals do not carry further? If your aerial system if picking up Welsh signals then you could of course filter them out, and indeed filter out all but Winter Hill. But this would only prevent them from being found in the first place. Manual tuning would appear to work around the issue for much less cost.
Freesat asks for your postcode so as to provide the regional programming associated with that postcode.
It is absurd to suggest that a sensible step is that the Freeview system should ask for the viewer's postcode. This is because the Royal Mail does not deliver RF signals!
At any one postcode there may be viewers with aerials facing different transmitters, this being particularly the case in areas of poor reception on more than one transmitter, but where no one single one is good.
Also, the fact that there is now "Freeview Lite" where many small relay transmitters carry only Public Service channels means that some people will wish to tune to a full-service transmitter that isn't as good a signal as the local relay.
| link to this comment |
John: There are two differing objectives of the postcode system employed by Freesat and that of any proposed for Freeview.
For Freesat, as you identify, all signals come from the same point, which is the satellite. All signals (for all regions) are available in places where the satellite can be received. Entrance of the viewer's postcode is simply so as to select the regional programming designated for that postcode.
You say that viewers "expect" to receive programming relevant to their area and this is true. If that is the object of a Freeview postcode system then clearly some will not only be disappointed, but without reception unless they resort to manual tuning which is something that I thought that postcode system was meant to alleviate!
In the real world, reception from a particular terrestrial transmitter requires there to be a good enough path from it to the base (receiving) location. Whilst Winter Hill may be clear-cut in your location, in others it is not so. Simply "wanting" a particular regional variant is not enough.
Some people receive regional programming that they do not consider relevant to their area because they cannot receive from a transmitter which broadcasts their designated regional output. In some areas, one house may be on one transmitter and another house on another, both of which are in the same postcode, and this may be because it is a poor reception area. Some may have a local obstruction such as a tree, building or land formation. As I say, the Royal Mail does not deliver RF signals.
If a Freeview postcode system were be put in place, then presumably each transmitter would broadcast the postcodes that it serves. This would mean that relays would broadcast the same postcodes which means that areas where relays and their parents (or multiple relays) overlap may have to manually tune. Thus the issue that you experience would still be so for some. However, it would mean that the "wanted" region would be selected even if it were being received from a transmitter other than that for which the aerial faces.
It is possible to select the correct region now and this appears as if it would produce the result you are looking for. But it is down to the design of the set-top box as to whether this is available. Every transmitter belongs to a Region/Network for which some receivers present the user with a list of those found. This achieves the same objective that you seek.
| link to this comment |
James Gardiner: Your receiver may have tuned to the transmitter for which the aerial was not installed for.
At your location, the bearings of the transmitters at Bristol Kings Western and Wenvoe are close, although the former is vertically polarised and the latter is horizontally polarised.
Look through to see if there is an option to change the region. Each transmitter will be designated as being of a particular "region".
Failing that, manually tuning to Kings Western, assuming that your aerial is vertical. Wenvoe's channels are interleaved so the unplugging aerial trick during part of the scan won't work here.
UHF channels are:
Kings Western: 43, 50, 46(HD), 53, 57, 60
Wenvoe: 41, 44, 47(HD), 42, 45, 49
For the HD multiplex, you may have to set the mode to DVB-T2, instead of DVB-T (for standard definition).
| link to this comment |
Steve Loble: No. Follow the link to HD Ready which means that a TV can show HD pictures but does not have the means to receive them off the air.
| link to this comment |
Mark G: Turn your aerial for vertical polarisation.
Rowridge uses mixed polarisation. PSB channels are 200kW vertically and horizontally whereas the COMs are 50kW horizontally and 200kW vertically.
There is no such thing as a "digital" aerial. In some cases a replacement aerial is required to receive digital (almost always the COM channels).
For Rowridge this isn't generally expected* to be necessary. By switching to vertical polarisation should benefit you will be expected to be taking advantage of the 200kW signals for all six multiplexes.
Rowridge uses only Group A channels and wideband yagi aerials have less gain on those channels. For this reason, a wideband yagi aerial is not advised and a Group A yagi may be the better bet. See here for more information:
Rowridge Transmitter
One final thing, the COM channel don't have as good coverage area. Small relays don't carry them, and of those that do, some viewers will only be expected to receive PSBs. See which predicts that around one third of Rowridge viewers will be PSB-only:
The commercial multiplex after switchover: ArqA, ArqB and SDN | ukfree.tv - 10 years of independent, free digital TV advice
Unfortunately the powers that be won't release the radiation patterns of the transmitters. This indicate how much signal is thrown out in each direction.
We had a report from someone a few miles south of Rowridge who lives in a dip and therefore can't "see" the top of the transmitter. He could receive the PSBs well but couldn't get anything on the COMs. We can only speculate as to whether this is because the COMs are severly restricted to the south, probably so as not to interfere on the Continent.
| link to this comment |
jay: All transmitters carry HD; it is the Commercial (COM) channels that carry the likes of ITV3, Pick TV, Dave, Film4 and Yesterday that don't have as great a coverage.
The only possibility appears to be from Saddleworth (of which Brook Bottom transmitter is a relay).
See if any of your neighbours have their aerials pointing at 41 degrees. They will be vertical, just as with Brook Bottom transmitter. Granted the difference in bearings isn't great at your location.
The Digital UK predictor suggests that you might be able to receive from Saddleworth, but it must be pointed out that such predictions are in no way an exact science and therefore should be taken with a pinch of salt. The difficulty being, well, you live in the "bottom" and as a result, you don't have line-of-sight to Saddleworth, Quick Edge being in the way.
If you can go down this route, then a replacement aerial will probably be required as Saddleworth uses Group B channels exclusively whereas Brook Bottom uses C/Ds.
For more information on aerials, see:
Digital TV Transmitters Nationwide Page 2
| link to this comment |
Tuesday 16 October 2012 11:43AM
Briantist: Does this mean that, theoretically, if the UK was to change from MPEG2 to MPEG4, then there would be room for more services (due to using less bandwidth)?
The Republic of Ireland has a single multiplex which carries standard definition services and RT Two HD so it is possible to mix them. Does Saorview use DVB-T or DVB-T2?
Is the advantage of DVB-T2 that it offers greater bitrate than DVB-T?