All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
Why all this fuss about HD/SD? Some don't have the HD equipment so enjoy their programmes in SD (625 line/50Hz interlaced). Other with the equipment capable of HD can watch some programmes in 1080 line/100 Hz progressive, giving a somewhat clearer image rendition.
I worked on the Eureka95 project and we had 1250 line/100 Hz progressive running in 1992/3! I also know that Radio Rentals, and maybe other rental companies, offered 1250/100 Wide Screen TVs at around the same time, but public take up was poor.
So for me HD = 1250 line/100 Hz, but 1080/100P is better than 405/50i I reckon.
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Reading these pages shows that some people seem to think that 4G in the 800 MHz band is already running, AFAIK it is yet to start! Though, to be strictly accurate, there are some small scale experiments being performed in a few areas occasionally. The current EE (Orange) 4G is in the 1800 MHz band so cannot directly affect DTTV (Freeview) which operates below 800 MHz. When 4G in the 800+ MHz band does start it is expected that very few viewers will be affected by interference and a few may benefit from a filter. But most people will not need a 4G filter and it could cause more problems than running without - especially as the 800+ MHz services are yet to start commercially. Those most affected could be in areas where Freeview uses the higher frequencies in the 700+ MHz range, few (if any) below that are expected to be affected and will not need a filter.
There also seems to be a confusion between Channel Numbers and Programme Numbers. Channel numbers were allocated by International Convention as an easier way to describe the frequencies used for transmission of sound and vision+colour. The Programme number is entirely at the users' discretion but broadcasters like Freeview and Sky like to predetermine the number used by viewers to display their wanted programmes. So normally BBC1 is on programme 101 (on Freeview and Sky) despite the fact it is actually transmitted on a number of different channels. Further, each channel on Freeview and Sky contains programme information for more than one programme service. So they should not be confused as they are different meanings and usages.
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Steve
Though I didn't see the programme, I can tell you that it is not an offense to ask for a Police Officer's number. As an ex-Special Constable with the Met, I know that we were required to allow any member of the public have and take note of our Divisional Number, that's why they are worn on the shoulders. I can't comment on the reason for the arrest as I didn't see the programme.
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Linda:
Do you mean that you get digital radio services using your Humax Freeview box? Freeview transmit up to 24 digital radio services, see http://www.freeview.co.uk…els, but they are not DAB services.
DAB uses a different way of broadcasting radio services and different transmitters, but the service is not available everywhere. I gather from Huntly Radio, for Radio in Huntly, Aberdeenshire, UK that DAB is available in the Huntly, Aberdeen area but reception depends on proximity to the transmitter and any intervening hills, tall buildings, etc.
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Alphathon:
After 50 years in the TV industry, there is no confusion in my mind! I never stated that frame rate or field rate were other than you say! I never stated how many of those lines contained picture information. That is all defined in the standards for 625 line TV transmission, as it was for 405.
I also never mentioned HD-MAC either! (Plus what is on Wikipedia is not always correct!)
Further, horizontal 'definition' in an analogue service is a product of bandwidth of the transmission channel (5.5 Mhz max for UK UHF TV with 8 MHz channel spacing in transmission) and the amplifiers within the TV set, especially the video output stage. This was traditionally limited to no more than 6 Mhz, but for teletext use it was often increased at the output stage for better clarity of the letters.
The Eureka95 project I was involved with had a horizontal bandwidth of 24 Mhz, 1250 lines total (including the blanking, data, framing pulses, etc) with a non-interlaced vertical scan rate of 100Hz. It never really succeeded as digital techniques were seen by regulators as the way forward. The analogue TV sets offered in the 1990's had to interpolate from 625/50i to 1250/100p and that introduced headaches of its own!
Some of the lines in analogue transmissions contained information to synchronise the horizontal and vertical scans so the image was formed correctly and didn't suffer from rolling (poor frame sync) or skewing (poor line sync). Not specifically required for the CRT but to synchronise the horizontal and vertical scans when shown on any display system. Plus some lines contained the teletext data itself.
Your paragraph on HD-MAC is not relevant as I didn't discuss anywhere the recording of TV programmes at any definition. Judging by the use of a horizontal definition in terms of pixels, I imagine you are discussing a digital system which is not relevant to my discussion about analogue transmissions.
Plus digital TV suffers from significant visual artifacts that many find disturbing and were not present in analogue services.
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The 2 Sky Sports channels are to be replaced with the 2 BT Sport channels in August. Much of the coverage will be football, rugby, tennis, MotoGP etc but many fans of other sports are less interested. BT do not have a price yet for these services after the first year free.
Those hoping to get the service via their broadband connect will, I'm told by BT, need a service of at least 5.6 Mbps, so many rural users will be disappointed. (I'm not despite a 2.1 Mbps ADSL line - I don't like football!).
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Mike Williams
It's worth pointing out that Freeview is not on any satellite so any change of footprint will not affect Freeview. FreeSat on the other hand is transmitted from a satellite at roughly the same orbital position as the Sky satellites.
Worth alos pointing out that to change the footprint of a satellite transmission will require physically moving the transmitting dish or the feedhorn, both mounted on the satellite some 39000 km above the Equator. AFAIK, the transmitting dish and feedhorn are not designed to be movable, not even by remote commands.
I'm not a user of Freesat, so I'm not sure whether there has been a change of frequency or transponder used for Channel 5, as I suspect from what Briantist says, perhaps other can enlighten us.
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Claire:
It is hard for anyone on this forum to help without knowing your postcode, or at least one of a nearby shop/Post Office/etc. An indication of what equipment you are using, such as what Freeview box and/or TV set you are using.
Then some here might know whether 4G has even started in your area yet, most have not yet, or if there has been a transmitter adjustment that may mean a retune is needed. It is hard to advise without the requested information.
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Steve P - and Terry:
In the analogue TV days we had co-channel interference due to troposheric lift and/or inversion layer effects quite often, especially in the summer months with high pressure systems dominating, as is happening currently. The modulation method has no bearing on the known atmospheric effects that give rise to the unwanted transmissions travelling further than normal and affecting normal reception. It has been known for someone living on the North Downs, in Surrey and Kent, to watch French TV programmes that normally are not receivable - except for the inversion effects. (As a TV service engineer in that area in the '60s and '70s we had to gently advise customers about it!) The effect has been well known in RF transmission spheres for many, many years and as it's a natural phenomenon there is nothing anyone can do about it (learn to live with nature and not work against it). It affects many RF transmissions, depending on frequency and the tropospheric conditions. Most large terrestrial TV transmitters are expected to cover not much more than 80 miles radius, but some more powerful sites cover more. But it is well known, in the 'right' conditions, for signals from a transmitter over 300 miles away to be received well enough to watch! The interference will seriously affect digital signals as well as analogue ones, resulting in either poor pictures and sound with pixelation or result in the signal not being decodable, so no picture/sound.
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Friday 14 June 2013 5:07PM
L Welch
Yes! I have never had Sky Sports (not a football fan) but do enjoy British Eurosport on my Sky+ box.