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Name                          Colm Scimone-Davies, Newport, Gwent            

Kit                               Sony KV29F1U TV, Panasonic NV-HD610 VCR, Yamaha DSP A1092 AV amp, Kef, Mordaunt Short & Tannoy speakers

Problem                      Colm is in a quandary; he is torn between a 36-inch Panasonic widescreen TV and a 41-inch Sony back projector. He has three questions. The first is which one produces the biggest image when displaying a 16:9 widescreen picture? Number two is which one has the best picture quality in widescreen mode, and number three, when will recordable DVD players be on the market?


Expert Reply             The big Sony TV wins hands down on picture size. According to our back of a fag packet calculations a 16:9 image on the Panasonic TV will be an inch and a bit narrower and almost two inches shorter than the one on the Sony screen. It gets even worse with 4:3 material, which on the Panasonic TV is going to be about the same size as you would get on a 28-inch 4:3 set. Picture quality is a tough one to call. A lot depends on the viewing conditions; back projectors work best in slightly subdued light, and the viewing angle is shallower, compared with a CRT. Picture tubes produce a brighter and contrastier image, colour fidelity is better too, compared with LCD projectors, but the impact of a big screen shouldn't be underestimated. We'll take the cowards way out on this one and suggest Colm uses his own judgement. The answer to question number three is probably within the next five years. The technology is available -- you can now buy DVD-RAM drives for PCs -- but the Hollywood studios are not keen on the technology, which has enormous potential for piracy.



Name                          James Broughton, Yately, Hampshire                 

Kit                               waiting for digital terrestrial

Problem                      James is curious about the frequencies that will be used to broadcast terrestrial digital TV signals; he also wants to know if he's going to need a new aerial?


Expert Reply             You would think it was a state secret after speaking to On Digital (the new name for British Digital Broadcasting) its press office told us curtly that such infomration won't be released until late September. That's odd because the frequency allocations have been on the ITC and DTG (Digital Television Group) web sites for some time. You can find them at: www.dtg.co.uk and www.itc.org.uk There's rather a lot of it, so please excuse us for not printing the whole list… Assuming James is already getting a good picture from his local transmitter (probably Guildford) he should be okay with the digital signal.





Name                          Gary Cheshire, via Email              

Kit                               buying a Philips 32PW6322 32-inch widescreen

Problem                      The spec for this TV are not very clear about its ability, or otherwise, to handle NTSC formatted signals. Gary says he has seen mention of 4.43 NTSC, but not the 3.38MHz system, he want's to know what the numbers mean as he's planning to buy a Region 1 DVD player? 


Expert Reply             The numbers refer to the frequency of the colour sub-carrier in a colour video signal. It is the difference in frequency between the colour and brightness components in the signal and it plays a vital role in the colour signal demodulation process. The NTSC system uses in the US is more correctly referred to as NTSC-M; this has a colour sub-carrier frequency of 3.38MHz.  NTSC 4.43(MHz) is another name for the partially decoded signal that comes from VCRs which have an 'NTSC replay' feature. The PAL colour television system used in the UK and much of Europe has a sub-carrier frequency of 4.43361875MHz (to be precise). In order to display an NTSC colour picture on a PAL TV the sub-carrier frequency has to be shifted, which is what NTSC replay VCRs do. All the TV has to do then is change the scan rate, to compensate for the reduced number of picture lines. The scan control microchips used in most recent TVs are common to both NTSC and PAL models -- this helps reduce the cost, most TV makers supply an international market -- so provided the colour signal has the correct sub-carrier information, it can be displayed.  Now as far as Philips TVs are concerned, we understand that all of their 50Hz models can handle NTSC 4.43 without any problems. NTSC 3.38 display (i.e. pure NTSC from US VCRs, DVD, LD players etc), is a feature on most -- but not all --of their 100Hz sets -- it is clearly stated in the brochures. Needless to say all 100Hz models can all handle NTSC 4.43 as well. Since the 32PW6322 is a 50Hz TV, you can take it as read that it won't work with an NTSC-only Region 1 player.



Name                          A. J. Datson, Newmarket, Suffolk

Kit                               Toshiba 3377DB Dolby Pro Logic TV, Panasonic NV-625 NICAM VCR

Problem                      A 'purring' sound on the centre-channel has been bothering Mr Datson. It only affects some recordings, and he tried the VCR on another TV (Philips) with the same results, which points to the VCR. However, this has been checked and pronounced healthy. So what is it, he asks, the tapes or the VCR?

Expert Reply             It's probably a bit of both, and not at all uncommon as we've had several similar enquiries in the past few months. The VCR alignment could be close to the limit and the affected tapes are probably slightly out of bonk, but still within the specification. When the two get together they react. What Mr Datson is hearing is undoubtedly the result of a minor tracking error. Accurate tracking is vital on VHS hi-fi sound system, which is why pretty well all hi-fi VCRs have dynamic auto-tracking systems that continually adjust for small errors. VHS stereo hi-fi sound uses the depth frequency multiplexing system, where the audio signals are buried deep in the tape's magnetic layer, a fraction of a second later they're overwritten by the higher-frequency video tracks. This weakens the audio signals, which have to read through the vision signals during replay. If the spinning heads are out by even the tiniest fraction -- whether due to a fault on the recording or mechanical misalignment on the VCR deck, the tape mis-tracks and the end result is usually a buzzing or 'purring sound. If it's only happening on a couple of commercially made recordings take them back and ask for an exchange. If it happens on lots of tapes including ones recorded on the VCR then it requires attention.



Name                          Dennis Spencer, Watford, Herts              

Kit                               buying a new VCR

Problem                      With digital TV just around the corner and a dead VCR in her living room Dennis wants to know if she should be thing about a future-proof model, or will existing VCRs cope with the new technology?


Expert Reply             Future-proofing in consumer electronics, you have to be joking, there's no such thing… Any VHS VCR will be able to make off-air recordings of digital broadcasts -- satellite or terrestrial -- picture and sound quality will be the same as you get on analogue TV. The only recording system that can do full justice to digital television is D-VHS, the first machines should be with us later this year, and prices should start at around £800. However, before you start placing your order it might be worth waiting a while, at least until you've got a digital decoder or TV and things will have settled down. Until then stick with good old VHS, or check out the new JVC HR-S7500 Super VHS machine, which has just gone on sale for just under £350



Name                          Janet Deeley, Nunhead, London                       

Kit                               combi TV/VCR query

Problem                      Janet quite likes the idea of a combined television and video. She has seen some Philips and Samsung models in a local dealer, but she want's to know if there's any problems with reliability, how big do they get, and do they have the same features as a separate TV and video recorder?


Expert Reply             A 'televideo' is no more or less prone to faults than an individual TV or VCR, though it's fair to say that some very early models were a bit cheaply made. Janet's concern is easy to understand though, if the one part packs up you loose both TV and video. Whilst that's possible reliability is improving all the time and we wouldn't rate it as a major consideration these days. Size wise, 20 and 21-inches is as about as big as they get, in the UK at least. There are rumours that at least one manufacturer may be working on a 25-inch model, but don't hold your breath, and if you can find room for a 25-inch TV, you probably have room for a VCR as well. Televideos aren't necessarily any cheaper…


Philips are leading the way with features, the 21 PV 688 is currently the biggest and best specified model on the market. It has NICAM stereo sound, hi-fi stereo recording, teletext and multi-standard operation.




You stare at them for several hours each day, but how much do you really know about TV picture tubes? The cathode ray tube or CRT has been with us in one form or another for over 100 years. The tube, as we know it today dates from the 1930s, the first colour CRTs were developed in the 1950s. Inside a colour tube there are three electron guns, one for each primary colour (red green and blue), (some designs split the output from a single gun into three streams). The electrons are accelerated towards the front of the tube by a high voltage charge, where they strike microscopic coloured phosphor dots or stripes, which then emit red, green or blue light. The trick is to make sure the right electron beam hits the right coloured dot or stripe. Inside the tube there's a thin perforated metal sheet, called a shadow mask or aperture grille, that makes sure the beams and the dots (or stripes) all line up. Aperture grilles are a feature of the Sony Trintron tube, they have slots in stead of holes, which let through more electrons to give a brighter picture. Shadow masks and aperture grilles get very hot and to prevent them from distorting, and generating colour faults, they're made of a nickel-steel alloy called Invar. Trinitron (and Mitsubishi Diamondtron) tubes have fine wires running across the grille, their faint shadows can sometimes be seen against a bright background.   


Tube manufacturers love teccy-sounding names, here's a couple to look out for. Black Matrix is a favourite but it tends to be a bit of a moveable feast. It usually means more closely spaced groups of phosphor dots, or 'triads'. Reducing the gaps increases contrast and colour fidelity. Black Matrix tubes can also have darker glass faceplates, also to improve contrast. The FST or flatter, squarer tube has a reduced radius on the faceplate, this cuts down annoying reflections, and allows manufacturers greater flexibility on cabinet design. However, the trade-off is a tube with a longer neck, which is why modern TVs are deeper than models of ten to fifteen years ago.





Name              John Nunez, via Email                                      

Kit                   Sharp XV-315P LCD projector, Panasonic A-110 DVD player 

Problem            When playing NTSC DVDs on his imported Region 1 player John notices that the intensity of the image slowly fluctuates, getting lighter and darker every 5 to 10 seconds. It doesn't happen when the DVD is connected other display devices, or when the projector is used with a PAL VCR, so what's going on?     


Expert Reply             This one is a bit of a mystery. The effect John describes is quite similar to that caused by some copy protection systems, when an attempt is made to duplicate a recording on a VCR. It may be that the video processing circuitry in the Sharp projector is sensitive to the protection measures, whereas a TV would normally be immune. The only way to check this theory is view an unprotected disc on this set up.            



Name                          Stephen Newton, Oldham, Lancs

Kit                               thinking of buying a Region 1 DVD player

Problem                      Stephen has noticed that a lot of the DVD players he's seen have a menu option for switching between PAL and NTSC, he would like to know what this does?


Expert Reply             Usually it's for setting the playback norms, in other words, specifying the type of discs that will be played, and the sort of TV to which the player is connected. In fact all DVD players automatically detect what type of disc type that has been loaded, but they cannot tell what kind of TV they're being used with. In some situations you may want to play back an NTSC disc on a PAL TV, or vice versa, (assuming the regional coding or the player will let you), this switch will allow you set the video output format. We have also come across players with PAL/NTSC switches on the back. There's one on the Grundig deck, the instructions somewhat confusingly refers to it as a switch for setting the on-screen display; though this also switches between NTSC and PAL output.



Name                          Clive Richards, Croydon, Surrey            

Kit                               Panasonic DVD-A100

Problem                      DVD has proved a frustrating experience for Clive. It's nothing to do with the performance, which he says he's very happy with, but as his collection of discs grows he's noticed the discs are coming in a variety of different shapes library cases. His problem is where to keep them all, and do we know of anyone who's making 'universal' racking systems?


Expert Reply             We can understand Clive's irritation. Looking through the discs we have in the office there are at least five different styles, including the standard CD 'jewel case', extended jewel case, and even a cardboard box... There doesn't appear to be an industry standard as such, though a lot of software companies now seem to be favouring the 'paperback' type, which opens like a book and is slightly smaller than an A5 sheet of paper. We have no doubt suitable stacking and racking systems will begin to appear once the format is off the ground. Several manufacturers we've spoken to say they're keeping a close eye on the situation. In the meantime there's nothing to stop Clive from using standard CD jewel cases for his DVDs and keeping them in a normal CD rack.



Name                          Terry Layham, Exeter, Devon            

Kit                               Sony SLV-E90 VCR, Hitachi C2848 TV

Problem                      No-one seems able to give Terry a straight answer. Whilst out and about looking at DVD players he has been asking dealers whether or not it is possible to make VHS copies from DVD discs. He says his question got mixed answers, from don't know, to can't be done. Can we settle the matter?


Expert Reply             From the technical point of view there's nothing to stop Terry from making analogue copies of DVDs on his VCR. All he has to do is connect the AV output from the DVD player into the AV input on his video recorder, using an ordinary SCART to SCART lead. However, there are a few points to bear in mind. Obviously it is illegal to duplicate copyright material, and if Terry tried to sell copies he could even end up spending time pleasuring Her Majesty, at the very least he would get a very heavy fine if caught. A lot of DVDs

contain copy protection signals that make analogue VHS recordings virtually unwatchable, but the question is why? There's no good reason to want to do it, apart from piracy. VHS copies will be a shadow of the DVD original, and you don't get any of the benefits the format has to offer, namely rapid access, multi-channel soundtrack, and interactivity.





You probably won't be surprised to learn that DVD has been having a bumpy ride in its other incarnation, as a high-capacity carrier of computer data and software. There's also some confusion over whether or not PCs will be able to replay DVD movies and the role the Windows 98 operating system has to play in all this.


There are now no less than four recordable DVD formats, either in production, or in the pipeline, which makes the fuss over regional coding and audio schemes look like small beer. The first product to reach the market is the Panasonic LF-D101 DVD-RAM drive, costing around £470. It looks like a regular CD ROM drive and it comes with 2.6 Gb rewritable disc. Two sided discs, with 5.2Gb capacity are also available. They're sealed inside plastic caddies, so they won't play on ordinary DVD-ROM/RAM or home deck drives. There is also a type of single-sided DVD-RAM disc that can be removed from its caddy. It gets worse, Hewlett Packard, Mitsubishi, Philips, Ricoh and Sony have stepped outside the DVD Forum -- the organisation which is supposed to maintain the standard -- and come up with another type of recordable DVD, called DVD+RW. The discs are as nature intended - i.e. no caddy -- but the sting in the tail is they can't be played on homedeck DVD players. Then there's the system developed by Pioneer, called DVD-RW, which apparently is endorsed by the DVD Forum, and lastly there's DVD-R, which is a write-once system, but somewhat specialist in nature and unlikely to have much of an impact in the consumer market.    


The answer to the other question is yes, PCs will be able to replay DVD movie discs, but only if they've (a) got a drive and (b) a suitable MPEG 2 decoder board. Rumours that Windows 98 would feature software MPEG 2 decoding are unfounded. If you really want to watch movies on a 14-inch screen it's cheaper to buy a DVD homedeck and a portable TV…



ã R. Maybury 1998 0708


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