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September 2003

Beechlog
 
The on-line magazine of the Burnham Beeches Radio Club.
Welcome to the on-line magazine of the Burnham Beeches Radio Club. Published whenever I find time to do so, this is the September 2003 issue.

Welcome to the September edition of BeechLog.

Yes, I know it's late again, actually this edition should have been out months ago. These days I don't tend to get access to my PC until after 11pm when everyone else has finished with it. That's my excuse anyway. If you think you could do better, just let me know, and it's all yours!

There have been great changes to the amateur licensing requirements since the last issue. I suppose that as a result, VHF will become deserted. I don't get much time on any bands at the moment, most of my aerials are down, and won't go up again until I've finish rebuilding the roof above which they are mounted. My rotator seems to be quite intact, and just needs a touch of lubrication. But the two metre beam; while the boom and elements are still serviceable, the bit of steel in the middle that joins the two halves together and holds it all aloft has a severe case of rust. Oh well, it's been up there at least 15 years.

This edition of BeechLog looks rather different - I decided to mess it about a bit, hope you like it! The content is the usual sort of stuff, whatever comes into my mind at the time. Articles from readers are always welcome, you know where to send them!

Roger GØHZK, Editor

Contents

The changes brought about in WRC2003
High quality sound recording, is it too late?
New amateurs
CD-Text?
Useful Links.

Some thoughts on WRC2003

After a couple of years of frantic discussion on usenet, WRC2003 has been and gone, bringing changes to amateur radio that some had hoped for, and others had dreaded!

There were many changes, although two have stimulated much discussion. Firstly the 40m amateur band is to be extended in six years time, we will receive an extra 100kHz making the future band from 7.0MHz to 7.2MHz in Europe. 40 metres is quite busy at the moment, so this relief has been welcomed by all.

The other main change is the elimination of the mandatory Morse test for access below 30MHz. From July 4th 2003, the Radio Regulations have changed to allow administrations to make their own decision on this matter. Switzerland was probably the first to drop the Morse requirement, and here in the UK the Radiocommunications Agency did likewise before the end of July. Thus the B intermediate and full licences have disappeared.

At the time of writing this, it is expected that amateurs with B licences will be allowed to keep their current callsigns and get full A licence privileges. This has caused much dismay amongst some amateurs, who had hoped that their imagined superiority over the B licensees would be maintained. For some reason, many amateurs are unable to unite with the others, and try to preserve an aloofness - this is not good for anyone, as we need to speak with one voice to governments and even to the public.

The main reason, to which they will never admit, is that they hate to see others earn licences without jumping through the hoops that they had to. To this day many amateurs refuse to recognise a licence earned by taking a multiple choice RAE, as they feel that the original essay-style exam gave them superiority. The Foundation licence is regarded as a CB licence given away in cornflake packets. Those who passed the 5wpm rather than 12wpm Morse test are second class licensees. And now they will despise and refuse to speak to those who received their A licence after this month. Luckily these folk are in a minority. Newcomers to HF will generally be quite happy not to speak to these gentlemen.

A good many of todays A licensees have always felt that the Morse test was an anachronism, and will be quite pleased that future amateurs will not have to go through what they felt was a pointless and out of date process. Morse seems inpenetrable to those who cannot read it, and since there never has been a compulsion to use it, why was it still required?

Morse is of course a useful mode. For most moonbounce enthusiasts, it is the only mode which survives the severe distortions the signal can suffer. Similarly with VHF contacts via aurora, the Morse 'tune' remains even though any semblence of tone is lost. Morse will survive while it is useful, and while amateurs enjoy using it.

But on HF there are 'new' modes which perform just as well and sometimes better. The capability of computer sound cards to perform FFT (Fast Fourier Transfer) has meant that modes based on contant tones can easily be 'dug' out of the noise. I remember when I was demonstrating PSK31 a while ago - while my radio was connected to a dummy load, I could still get good copy on completely inaudible stations. FFT and PSK have been used outside the amateur sphere for decades. I worked on FFT sound recovery over 20 years ago, and it was also used on other weak-signal systems and deep space projects back in the sixties.

So from me, good riddance to the Morse test. Morse can now 'stand on its own feet'.

High quality sound recording, is it too late?

Having changed my car recently to one fitted with a CD changer, I have been going through my CD collection and making copies for the car. The intention here is not to deprive the copyright holders of their justified income, but to avoid the loss of my CDs to any light-fingered member of the public who may decide that my car or CD changer is better off liberated from my ownership.

I have mentioned before that some CDs are copy-protected, which would mess up my good idea. I recently thought that I had found such a disk - Pink Floyds 30 year old Dark Side Of The Moon, as the disk failed to play in the DVD drive I use as the source in my copying process. But finding it played OK in my CD writer, I looked more closely.

It turns out that the disk in question is not a normal CD - in fact it's a Hybrid SACD, so a bit of research was required - I hadn't realised that such products were available in ordinary shops. There are in fact two rival CD replacement technologies being introduced: SACD and DVD-A.

The object of these products is to build on the current CD technology and eliminate the drawbacks of current CDs. The basic idea is to eliminate the "CD sound" that upsets many purists. This has been done by increasing the resolution of recording, both in sample rate and ample resolution. But these two products are very different in how they do this. SACD uses a new bitstream process that removes the need for the heavy filtration necessary in CD systems, while DVD-A preserves the Pulse Code Modulation of CD but relies on new technology to reduce the side effects of this process.

Browsing the net for information is quite interesting. There is a large amount of misinformation published there, which draws attention to the fact that these systems are rivals. The DVD-A camp seems to be the major culprit here, and I read a great deal of information that was simply untrue. Of course the SACD side drew attention to what it claimed were deficiencies of DVD-A. Ordinary people can make their own judgements - look around and see what is actually available, music and equipment.

In practice, the musical qualities provided by both these technologies show an improvement on CD. Each have their strengths and weaknesses. It seems to me that each will appeal to different groups of people. In particular DVD-A is a more versatile specification and will indulge in all sorts of things which will apeal to the Home Cinema enthusiast. It can store a varying amount of music depending on data rates and resolutions, from 40 minutes at the highest quality, to almost 24 hours of CD quality stereo. Using many tricks inherited from DVD video, there are interactive menus and graphics, and a bewildering range of setting for both playback and at the recording stage. It is not surprising that almost all DVD-A players are also DVD video machines. Do not expect these machines to produce the best quality audio however. SACD plays few tricks but concentrates on audio quality. I suspect that it will be geared towards hi-fi enthusiasts - standalone players and audio systems are likely to be the norm, although some Sony DVD videos will also play SACD disks.

The latter point shows how things are polarising. It is interesting to consider who makes what, and much more interesting to see who does not! Sony does not make DVD-A disks. Warner does not produce SACD disks! SACD hybrid disks (which have a CD layer and thus can play as ordinary CDs) are available, like my Pink Floyd disk. The DVD-A spec also caters for similar hybrids, but its proponents do not produce them for commercial reasons!

What do SACD and DVD-A have in common?

Both systems are basically designed to meet the same requirement for high quality audio. So a good number of properties are the same or very similar. Both use a DVD style disk, the same diameter and using the same manufacturing technology.

Both are designed to play both conventional stereo and/or 6 channel audio. In most cases the latter is configured as 5.1 surround sound. Both systems can store full titling information, i.e. track titles, performers, indexes etc.

They can also store text, graphics, video and additional data. Copyright information, copy protection, and other anti-piracy measures are available.

Both support dual layer recording.

SACD properties.

The SACD uses a completely different system to record its audio data. This is called Direct Stream Digital (DSD). Normal CD uses Pulse Code Modulation, where the audio is split up into voltage samples stored as a 16-bit word. These samples are taken at a rate of 44.1 kHz.

DSD doesn't use PCM, instead it samples the audio at 2.8224MHz, and records a "1" if the voltage is higher than the previous sample, and "0" if the voltage is lower. This process eliminates one of CDs biggest obstacles to high quality sound - the brickwall analogue anti-aliasing filter is no longer required. Instead filtration can be much more modest, and can even be carried out in the digital domain. The problem with this 1-bit data stream is that it generates quite a bit of noise. However the solution was discovered in 1954 (DSD was conceived in 1946!). You simply design a feedback loop around the quantizer, measure the error from one sample and subtract it from the next. This apparently pushes the noise up to very high frequencies. This system is called "oversampling delta-sigma modulation".

Now the result of this system gives us a frequency response of DC to 100kHz, and a dynamic range of 120dB! In order to reduce high frequency noise being fed to loudspeaker systems, SACD decrees that recordings are made using a 100kHz low pass filter, and that players must use a 50kHz low pass filter on the audio output.

The digital data is compressed using "Digital Stream Transfer" which is a lossless high speed technique. The actual capacity of the high density layer of the disk is 4.7 Gbytes. This is split into several sections. The tracks nearest the centre carry the SACD stereo data, the centre section carries the surround sound data, while the outer tracks carry text, graphics, video etc. The CD compatible property is realised by having a second layer inside the disk. The 780 nm CD laser passes through the SACD high density layer, and reflects off a CD layer in exactly the same place as on a normal CD. To counteract losses through the high density layer, the usual aluminium CD reflective coating is replaced by a more reflective metal (I don't know what this is!). Note that not all SACD recordings have a CD layer, some recordings are SACD only.

The playing time of an SACD is nominally the same as a normal CD. To achieve the high capacity, a 650nm laser is used, with a smaller aperture, closer pitch, and generally tighter tolerances than a CD - these allow a larger playng area.

DVD-A properties.

The DVD-A system is an extension of the techniques used for normal DVD video. The latter gives you a choice of several techniques - Linear PCM, Dolby Digital, MPEG-2 and DTS. The usual is Dolby, with a 48kHz sampling rate and 24-bit audio. A lossy compression system is used. DVD-A has a similar range of choices, several may be present on one disk. There is a range of sampling rates between 44.1kHz and 192kHz, and word lengths of 16, 20 and 24 bits. Any number of channels between 2 and 6 are allowed.

The actual choices available are limited by the maximum bit rate of 9.6 Mbit/s. Thus the highest quality cannot be achieved for surround sound. However 96kHz 24bit surround sound is possible due to the adoption of Meridian Lossless Packing, the compression system adopted. DVD-A can also derive a stereo output from the surround sound track. A system called SMART is used. This stores the bit mapping coefficients in the audio tracks, i.e. an individually tailored recipe is available for each music track. This eliminates the need for a stereo track, although the latter track is possible.

Also the bit rate and word length may vary between surround sound channels, thus saving data on the less significant channels. At its highest sampling and bit rates, DVD-A is capable of an audio bandwidth of 96kHz, and a signal to noise ratio of 144dB. What you actually get may be less, as a DVD Video compatible track may be included, and maybe video, graphics etc.

Like SACD, a single layer can hold 4.7 Gbytes. This is achieved by similar means as SACD. The directory structure is identical to that of DVD-video. Two layers may be present, giving nearly double the capacity. CD compatible layers are not used however.

Which is the best?

Not an easy question, it depends what you are expecting from the new media. The success of either will also depend on the skill with which they are marketed, remember the VHS vs Betamax contest of 20 years ago. SACD is backed by Sony and Philips, and DVD-A by Warner and Panasonic/Technics. There are probably more SACD titles around, which cover more music genres, aided by possible 'stealth' introduction of hybrid disks - like me, you may already own SACD disks without realising it.

In order to play these disks, you will need a player, and once again you may already own one without realising! Your DVD video player will most likely play DVD-Audio disks. It will probably play DVD-Video compatible tracks which may also be provided on the disk, but more advanced DVD players will play the higher quality DVD-A tracks. If you have a Philips or Sony DVD player, this may also play SACD disks at full resolution, and this facility may also extend to other DVD manufacturers by now (probably excluding Technics/Panasonic!). Pioneer and others also manufacture machines that play both formats.

The only drawback with using a DVD player is that the circuit design may not take full advantage of the high performance media. Even now some CD players sound better than others - years ago it was discovered that by the simple act of replacing electrolytic capacitors by better quality items could actually improve CD replay quality. You pay for what you get.

Best sound performance will be obtained by using a dedicated player. There are standalone SACD players, designed to replace the CD player in a high quality audio setup. These players are also designed to play CDs at the highest quality. There are also SACD players that also play DVD video. Regarding DVD-A, most players are designed to play DVD video too, this is probably necessary anyway in order to exploit the menu system and other visual enhancements.

There are some players that cope with SACD, DVD and DVD-A. Reviews seem to suggest that these too are a compromise, but still able to show improvement over CD.

These players are priced over a wide range. Those that are based on domestic DVD video players are not expensive - say £150 upwards. However the standalone versions can be very expensive!

While the audio quality of the cheaper players may not be as good as the best CD players, they will play your disks in Surround Sound, which may be all that you want. While this probably benefits all music, some types will take advantage of this capability. Popular music genres may well use Surround Sound to achieve spectacular effects. Any any music with a spatial aspect may be enhance - for example opera and oratorio. Centuries ago composers like Handel used groups of singers located all around churches - in front, at the rear, at ground level and in balconies - the new media should be able to reproduce these arrangents as the composer intended.

Surround Sound does place some obstacles to the average householder - like where to put the speakers. The small size of modern rooms poses limitations, it's difficult enough even for stereo! But since the proponents of DVD-A say that 25% of all DVD systems are already connected as Surround Sound, who am I to argue?

So what's the audio like? Does it give "The closest approach to the original sound"? My ears are aged, probably blown up in the "1832", a progressive music venue of around 1970 (actually a crypt under a Windsor church). So I can only report what others have said.

Both flavours offer improved results, provided of course that the recording, and the playback equipment is up to scratch. SACD is reported to give an analogue sound, smoother than before and lacking the CD effects caused by PCM and filtration. DVD-A is apparently more "transparent", but still shows the occasional CD effect. There are some recordings available in both formats, but it's still difficult to compare because the resolution of DVD-A will vary according to how much the producers want to fit on the disk.

Playing time.

DVD-A has the advantage of greater playing times. Those who listen to opera may well benefit from this. The drawback is that as you increase playing time, the sample rate and/or word length may have to reduce, i.e. quality may be less.

This is not so easy with SACD, because the resolution is fixed at the highest possible. More playing time would be possible by reducing the number of tracks, e.g. ditching either Stereo or 5.1 Surround Sound. Of course, if you buy an SACD changer, playing time is less important.

Whether this is important is a personal matter. The only time I get to listen to a whole CD is when I'm driving long distances!

The media.

Both DVD-A and SACD use similar media. The former is the same as DVD video, and the latter is very similar. My SACD costs £9.99 in the high street, there are some cheaper titles too. The average price of both media is similar to full-price CD.

Production.

Original digital recordings were made using PCM, and more recently recording has switched to DSD. The reissue of older recordings in the new format poses interesting issues. Remastering to the new formats is possible entirely in the digital domain, so CD sound can be reduced substantially. Those PCM masters produced with higher sampling rates and 20-bit (or more) data are more likely to to improve on the original CD when released as DVD-A or SACD, and reports of reissues bear this out. However mixing an original stereo or multitrack source to Surround Sound is unlikely to produce natural results. This won't matter much with popular titles, where natural sound is rarely required. But for classical and purely acoustic music it's a different matter.

Producers of new recordings will have to consider Surround Sound from day one. It's quite possible that this is happening now, as there is a growing market for DVD videos of classical and popular music.

Other formats.

When researching this article, I discovered that there are several other extended CD formats in production. There is HDCD, a 20-bit/44.1kHz extension of the CD standard, and XRCD, which is similar. The extra bits are encoded using smoke and mirrors, in such a way that the disks will play as 16 bit on ordinary CD players. I suspect that this actually reduces the CD playback quality, although playback on dedicated machines (are there any?) is better. But these are still PCM, and presumably suffer from the effects of 20 bit D-A conversion and brickwall filtering. With the introduction of SACD and DVD-A, these formats will surely die.

It's probably worth noting that there has been effort to improve the sound of currect CDs. The sound defects associated with PCM at 44.1kHz were realised many years ago, and two processes were developed to reduce them. Initially oversampling was used, in an effort to push the nasties well above the audio bandwidth. Digital filtration was adopted in the hope that it might sound better. Then bitstream players were introduced, which convert the PCM to a DSD-like stream before creating the analogue output.

The high-end versions of the latter do improve matters, but they cannot put back whatever was lost in producing the original 16-bit master.

Final choice.

For me it's SACD. One: I can play the hybrid disks on almost any CD player now, and get a SACD player later. Two: Following from point one, I can play the disks as CD in my car (I've already made a CD-R copy of the Pink Floyd SACD for the car). Three: I can rip the CD tracks to mp3 or similar (ripping high resolution tracks to the PC is an interesting proposition!). I can play the disks on my PC (as CD) too. Four: I can't see me being allowed (by my family) to play Bach or 1970 underground on the DVD player using the telly! But for others, DVD-A may make more sense. For me, the lack of a CD compatible layer means it's a no-no. Why did they do this? Maybe one day cars will have DVD-A players, there'll be DVD-A walkmen, and DVD-A Winamp. But the mp3 revolution is growing, who's going to buy a DVD-A if they can't rip it to their iPod or Zen! Perhaps Warner are doing this as an anti-piracy measure? But it seems to me like an anti-sales measure.

New Amateurs

At the beginning of August the club held another course for the foundation licence. Our thanks go to everyone who made this possible. This time there were nine students, and it's good to report that everyone passed the final exam.

The Foundation syllabus has changed a little since then, and the exam will have more questions. But this is mainly fine-tuning, as the intentions and the basic requirements are still much the same.

Helping out in whatever way you can is an opportunity to put something back into amateur radio. Don't listen to the moaners, who talk about this being the final nail in the coffin, but come along and help next time we run a course. Even if you just informally talk to the students, this is a great help, as they are full of questions that can only be answered by real amateurs.

Much of the resentment from the moaners comes from the fact that many of the students have a CB background. Is this so bad? At least it shows that they have an interest in radio, and a desire to progress. SSB CBers, provided that they don't blot out the neighbours TV reception, can carry on with little liklihood of a visit from the RIS. So they don't have to join our ranks, but many have chosen to, so they should be welcomed.

Of course, we will find some CB lingo on the bands. But remember that thousands of CBers joined us in the early eighties, and in my opinion, they have benefitted us. Looking back at my old logs, it seems that there were plenty to speak to on the bands, even 70cm, plenty of VHF DX, and you were never alone if you had a two metre radio in the car. The CB lingo will slowly disappear, as it did before. Some of the newcomers will become very technically proficient (if they aren't already), and many other will repay us by encouraging the next generation.

CD-Text

Sorry to harp on again about audio - I've been playing with rcording it since I could use a soldering iron. I recently made a discovery after buying a new portable CD player. It's a Sony model which also plays mp3 and ATRAC recordings.

The mp3 recording technique really caught on after the Napster file sharing system appeared. Forgetting the stuff about copyright, mp3 appeared to be a really useful way of circulating audio. File sizes were reasonable, and the audio quality quite acceptible.

ATRAC is a system invented by Sony for its Minidisc. This started out with the intention of compressing the music from a CD onto a Minidisc with about a quarter of the CD capacity, without any noticeable quality loss. More recently the compression was developed to further reduce file sizes so as to enable the storing of about 5 hours of audio on a minidisk, and about 24 hours on a CDR..

Anyway the player works as expected, but has a capability that Sony do not advertise - popping in my Pink Floyd SACD, I was surprised to see the track titles appear on the display! I initially thought that it was reading titles from the SACD data, but this was dispelled when I tried playing a CDR copy of the disc - the titles were still displayed.

I had never seen this before - the SACD was using a little-known CD property called CD-Text. So far I have found only three CDs that do this, although no doubt there are others. I guess that most CD players do not have an alphanumeric display, so there's been no incentive to add titles.

Useful Links

Here is some information on Direct Stream Digital, on DVD-Audio, and SACD.

Rogers Locator calculators, I'm slowly getting the bugs out, and one day should be able to refine the code a bit.

If you want to find out more about messing with GPS and mapping systems, here is the place for reliable info on the UK systems.

The BBRC Events List.