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April 2004


Beechlog
 
The on-line magazine of the Burnham Beeches Radio Club.
Beechlog
The on-line magazine of the
Burnham Beeches Radio Club.

Welcome to the April 2004 edition of BeechLog.

Hopefully this issue should be out on time, as I started it soon after the last issue was finished. As usual, it reflects the thoughts that were going through my head at the time! Honestly though, with redundancies being announced at work, I did wonder whether I would have more free time to write BeechLog, but as it turned out I still have to get up at 5.30am and drive to Reading.

I have been thinking about more radio stuff, particularly ATUs and small HF aerials, but haven't come up with anything interesting. I was thinking of trying some low power PSK working, but the lead with the Tx/Rx switching seems to have caught up in something, and the opto-isolator has gone missing. Since I was made redundant from the company that had stacks of these, I suppose I shall have to get out my wallet.

Roger GØHZK, Editor

Contents

Club web address
More keyboards
Illustrating Beechlog
Dodgy disks and washing machines
WSH?
Some recent contacts

The clubs web address

There was a message on the reflector a while ago regarding the choice of a more intuitive address for our web site. The problem was that all the sensible addresses bbrc.something were already in use. These initials seem to be rather popular, and unless we went for something like bbrc.br we would have to choose something longer.

However a few new top level domains have become available, like .biz, .me and so I grabbed bbrc.info before anyone else did. It seemed appropriate for a site giving information on the BBRC. So far I have just put up a page vaguely similar to the official club site, but when I get a bit of time I shall change this. My idea is to have a single link to the usual club site beam.at/bbrc/ and devote the rest to, well, info on the BBRC aimed at outsiders. What the club does, what amateur radio is, how to get a licence, and so on. Any help will be greatly appreciated - just your ideas, you don't have to write anything (some hope)!

More keyboards

While writing the piece about the Mellotron for the last issue, I couldn't help thinking about the history of keyboard instruments. There has been a very slow evolution over at least ten centuries, and it is surprising to note that the current keyboard layout has not changed much in nearly 600 years. Before then the mechanism for playing notes on a pipe organ was much less sensitive, and it required the action of a heavy fist on a broad key to sound a single note. But apart from that, a millenium ago, organs were getting highly developed, that of Winchester Cathedral had about 400 pipes and required several dozen men to work the blowers.

The forerunners of todays keyboard instruments were the dulcimer and the psaltery (pictured). These instruments, rarely heard today, were small boxes with a number of strings stretched across them. The dulcimer was played with hammers, like a xylophone, and the psaltery was plucked, like a zither. They looked quite similar, and sometimes one intrument served both functions. These were popular instruments 600 years ago, and fulfilled the function that the guitar would in later years.

Eventually the organ keyboard was married to these instruments to produce new instruments, the clavichord and harpsichord families.

Clavichords were descendants of the dulcimer, and produced a quiet but expressive tone. The first ones obtained different notes by hitting the same strings in different places, making many chords impossible. Harpsichords (including virginals and spinets) plucked the strings, and were much louder, and became the foundation of most orchestral music from the seventeenth century.

The harpsichord was limited by the mechanism used to pluck the strings, the attack, decay and volume produced could only be varied a little, so other mechanisms were devised. Knobs like organ stops enabled the player to pluck several strings simultaneously by pressing just one key. Typically there would be a pair of strings tuned as normal, and another pair tuned an octave higher. There might also be another pair of strings tuned an octave lower. Two manuals were usual, and by pulling out knobs above the keyboard, different strings were assigned to each manual. Other knobs and pedals controlled other tricks, like cloth dampers to reduce the decay time of the notes, and venetian blinds to vary the volume. These developments made the harpsichord a vital solo and orchestral instrument.

Before it was superceded, a vast amount of music was written for the harpsichord. Bach, Handel, Vivaldi, Scarlatti were well known exponents, but much Mozart and even Beethoven compositions were written for the harpsichord.

The harpsichord developed into the piano. Although the latter uses struck notes like the clavichord, the piano was devised as an improvement on the harpsichord. Music came to be written with either instrument in mind, such as Beethovens 'Moonlight' sonata, although I've never heard it played on the harpsichord.

What's this got to do with radio? Well nothing really, although I could have written about the concertina, an instrument invented by Sir Charles Wheatstone, who also invented the electric telegraph and of course the resistance bridge.

But back to the harpsichord. Last time I mentioned J S Bach's Goldberg Variations, written in the eighteenth century for one of Bach's pupils. This was written for the harpsichord, and consisted of a air, thirty variations (I miscounted last time!), and the air again. Being quite a difficult piece to play, it became neglected as there were plenty of showy solo pieces that performers could play. In 1955 a Canadian pianist, Glenn Gould, recorded the Goldbergs played on a piano. Both Gould and this music were relatively unknown at the time, but not for long. In fact Gould recorded it again many years later, and I think both recordings have been available ever since. The Goldbergs benefit from a particular sort of performer, and few have produced music to equal Goulds performances. Gould himself was a unique player, you can hear him humming, grunting and singing as he plays. To some people, this is awful, but there is no doubting that the music comes alive. Last year a new recording was issued, the piano again, played by Murray Perahia, an American who has recently produced some superb recordings of Bach concertos. Although a modern pianist, Perahia does not show off, nor does he distort Bach's composition to suit his style. And he keeps his mouth shut while he plays! I'm no musician and would not attempt to judge which performance is the best, but I wouldn't mind betting that Perahia's Goldbergs will satisfy all but those who must find fault with everything.

On to a different sort of recording, White Noise's An Electric Storm. I played this to my 19 year old son, who gave me a funny look. No it's not like Black Sabbath or Metallica. In fact it's not like anything else.

This recording was published in 1968. A number of musicians were involved, probably none that you have ever heard of. There are various singers, a drummer, and the other 'instruments' were 'played' by Brian Hodgeson and Delia Derbyshire. These two had a day job in the BBC's Radiophonic Workshop, Delia is best known for the Doctor Who theme which she produced from Ron Grainers score.

There is quite a story to this recording. In fact it is another reminder of the age of the Mellotron, as in these pre-synthesiser days, the sounds were produced by tape recorded samples. The Mellotron tapes contain recordings of conventional instruments and voices, but the tapes on this recording contain many unrecognisable sounds. These samples were slowed down or sped up, filtered, modified and whatever, and played by cutting and splicing short lengths of tape to produce each layer of sound.

An Electric Storm is not a musical masterpiece. But for old folk like me, who also messed about with splicing tapes and playing instuments through ring modulators, it's wonderful. One of those recordings which brings a silly grin to my face.

Finally, a couple of weeks ago, a 'Roger must have' film was released on DVD. This is another black & white affair, 4:3 aspect ration, no surround sound. By now you will realise that my tastes are not like yours. This one is not in English but Czech, directed by Jiri Menzel in 1967, Closely Observed Trains. It's about Milos, an apprentice working on a railway station in German occupied Czechoslovakia. Made under the communist regime, it's a wonder that it was allowed at all. Milos is trying to learn about girls, while his boss is learning about the military munitions trains.

This is nothing like anything Hollwood has produced. But it won the Oscar for the best foreign film in 1968. Like many British films of the late fifties, it's about ordinary people living ordinary lives. I'm not going to describe the plot, this film has to be seen right through. It has been on the telly, my wife walked out halfway through, but she likes Hollywood stuff where no-one has a proper job and yet live sumptuous lives, and which you can watch with your brain shut down.

It's a fabulous film, one of my top 10 of all time. Don't worry about the Czech language, the subtitles are fine.

The next few DVDs I plan to buy are all black & white too. Do they make anything worthwhile these days? Doesn't seem like it to me, I suppose it's my age. I never thought I'd get like this!

Illustrating BeechLog

Beechlog has been a bit bland in appearance recently, I suppose it's partly because all this stuff has been written at the last moment, without time to find suitable illustrations. So is this issue I thought I could go on a bit about pictures and how to make them.

I have been grumbling on Cix about the lack of progress in photography, particularly the digital variety. Well, not many people agreed with me, and I had to conceed that they did have a point. The problem as I see it is that as cameras evolve, they get more controls and functions and it becomes an ergonomic nightmare to find where to put them. My film cameras are pretty simple - there are shutter, aperture, focus, timer, film advance, and not that much else. But in the electronic realm, there are numerous variations around these, particularly with regard to automation.

For example there is white balance. On a film camera this was adjusted in two ways - by choosing a 'tungsten' or 'daylight' film, and doing further correction in the darkroom. Electronic cameras don't have film, so they have to cover the full range of possible variations. This means having an 'auto' setting, individual settings for daylight, fluorescent, flash, etc, and then a manual procedure for when none of the fixed settings seem to work.

Then there are numerous auto and manual focus settings, metering settings, image size and compression, contrast, sharpness, saturation, exposure compensation, flash modes, and much more.

Arranging all this so that you can find the setting you need leads to all sorts of different designs. More often than not the information and settings are displayed on a screen in characters one millimetre high, OK for 18 year olds with perfect eyesight, but no good for radio amateurs whose eyes can only focus on a Yaesu tuning dial or beer pumps.

Well, if you wish to buy a camera that will suit you, you have a problem. There are lots of glossy magazines in the shops, which have maybe up to two pages of 'review' copied from the camera distributors handouts, but these are generally a waste of time. Luckily there are a few good web sites which contain extremely detailed reviews uninfluenced by manufacturers. For example Digital Photography Review and and Imaging Resource. These sites contain extremely critical comment, and reading through them you see everything that's wrong with the cameras as well as what's right. So you need to be a bit careful with your interpretation, and avoid getting too concerned with stuff that isn't really going to affect you. There are also plenty of comments from owners in various forums. These often show dramatic disagreement with each other, "all the pictures were blurred and out of focus" was an unlikely review of a camera costing nearly £1000. Some of the stuff in these forums is quite useful, with clarifications of the Japanese "English" text in the sometimes baffling owners manuals, and "how to" information on getting round apparent limitations and problems. But the reviews in the forums just serve to confuse.

If you have owned an electronic camera for a while, you soon find out what is important to you. With me it is focus verification, exposure, ergonomics (you soon forget how to set certain things, even if the manual was clear and understandable), and seeing what's on the display. Finding a camera that improves on these things isn't easy, even if there is unlimited cash to spend! With some of these it is really a matter of reading the manual and learning to use the camera. For others, like the displays, you have to annoy the sales droids in all the local shops, and try them out. I'm currently experimenting with a camera with an elecronic viewfinder. These are despised by many users, as the displays are not perfect, but have the advantage of being adjustable to suit eyesight defects - I can really see the settings! They are also good in bright light, which can make lcd screens difficult to see because of reflections. And you can compose through them, and steady the camera against your face rather than have to hold the thing out in front of you.

Incidentally the price of digital SLRs is coming down. You can focus properly through these, as they have a normal ground glass type of screen. The Canon EOS300D set the ball rolling, it's now about £800 in the shops, and there is a Nikon competitor on the way.

You can't really focus through electronic viewfinders, but some cameras have little markers that 'light up' and show you what part of the picture is in focus. Mine has a "manual automatic" mode where you can move between these preset markers with a control, and choose which part of the picture is used for focussing.

There are numerous exposure modes on cameras too. There are matrix systems, where the picture is divided into maybe hundreds of areas, the results of which are used to calculate exposure. Then there are centre weighted systems, spot metering, exposure based on the area chosen for autofocus, and manual focussing. Probably more too. When you select one of these, a little icon appears on the screen, but whether you can remember what the icon means is another matter!

However there is one aid that is useful for judging exposure, the histogram. This is simple a graph showing the distribution of light and dark areas on the screen. The left extremity shows absolute black, the right is maximum white. Ideally a well exposed picture will tail away at each extreme, with one or more peaks in between. If the graph is squashed up the left side, then the picture may be underexposed, and likewise overexposed if the graph is up against the right side. You need to use your loaf here, if there is a large black or white area in the picture, then all may be well. Some pictures may need careful interpretation - a large area of luminous cloudy sky may make the range of brightnesses too great for the sensor, so you may have to put up with over- or underexposure in parts of the picture.

The building & grass occupy the first hump, the sky is of mainly even brightness and is concentrated into the spike on the right. Here most detail is preserved, but the sky is partly overexposed. The black areas in the sky actually flash on the camera display to indicate what parts are overexposed. This picture has a limited brightness range, and shows how the camera exposes the picture to put the subject in the middle of the brightness range.

If the graph is squashed up one end, you can operate the exposure compensation control to increase or decrease the exposure a little. Bringing the range of brightesses within the range of the sensor may mean the result looks wrong, but this is easily put right on the PC - if you had not adjusted the exposure you would not be able to recover the information lost in the overexposed highlights or underexposed shadows.

So looking at the histogram gives you lots of useful information - and some cameras have a live histogram display to enable you to get it right first shot (hopefully).

One other problem that annoys me is the tendency for digital cameras to exhibit chromatic abberation in certain conditions. The is easy to demonstrate at this time of the year, by photographing the bare branches of a tree against a bright sky, with the sun at the side or back. This effect usually shows as a purple border where there is the high contast between the thin near-black branches and the pale, bright sky. Sometimes you get a green border too, although this is usually less noticeable.

Chromatic abberation is well known in film cameras and is due to shortcomings in the lens. I'm not so sure this is the same in digital cameras, as the sensor may play a part here. But all digital cameras have this problem to some extent, some worse than others. One of the latest cameras is reported to suffer from this problem - the Sony F828. Its predecessor the F717 was a particularly fine camera, used widely by the press, but this recent upgrade seems to have regressed, even some magazine reviews have noticed this. Whether this is a worry depends on the type of pictures you take. If you like trees in winter sunshine, you need to borrow various cameras to see how they perform. Find a camera shop in a road with trees, and take along a selection of memory cards! It's fair to say that most 'normal' photographs will not show this effect, even trees photographed from the sunny side may reduce the contrast enough to prevent it.

I mentioned focussing earlier. Modern cameras can be very good at doing this automatically, but it helps to know how the process works, especially in situations where the camera may have problems. This may occur on low light, for example. Cameras focus by measuring the contrast between two adjacent areas as the lens moves. If you imagine a white string dangling down a dark grey fence, the string appears narrowest when in perfect focus - it spreads out when out of focus. The camera reads the values of a row of pixels, and varies the focus to the point at which the geatest changes are seen. Image a line through the string, and plot a graph of the brightness of each pixel - when the string is correctly focussed there will be a higher, narrower peak than when the string is out of focus.

When plenty of light is shining on the subject, contrasts are high, but when the light is dim they are low. Some photographers shine a laser pointer on the subject while the cameras is focussing, and some cameras have a 'focus assist' light. Both these methods can focus in complete darkness! But if you can't do this, there are other tricks. If you can restrict the area of view used for focussing, do this - you can often set cameras to focus on just a small central area. Then point the camera at something contrasty at the right distance, and press the release button half way down to lock focus on this. In dim pub lighting you may be able to focus on the light reflected from a glass or bottle. If it's a distant scene at night, just set the camera to focus close to infinity. Or in the worst case, use manual focus.

As you can see, there are usually ways around camera shortcomings, if you learn these then you can improve your photographs. Read the manual regularly, search the net for useful techniques, take plenty of practice shots (after seeing some of my practice shots, my wife went away shaking her head).

As you can see, there are a few pictures illustrating this article. I know there are no shots of aerials and the like, it's difficult to get a good composition of a G5RV or similar dipole! Getting these to a suitable file size is another story, browsing amateur sites on the web reveals that many people can't do this. Recently there was some comment (in the uk amateur radio newsgroup) about clickable thumbnails on one amateurs web site, he had used the large photos as thumbnails by specifying the display size in html. I posted some code which enabled him to fix his problem, but was chided by the others for helping him and spoiling their game!

Dodgy disks and washing machines

Recently I wrote about installing a new DVD writer into my PC. One of the reasons for doing this was to simplify the process of making backup copies of the data I fancy I don't want to lose.

I have actually paid out real money on buying software help with this job, so now all my 'vital' data gets automatically copied to a different hard disk every few hours, which in theory enables me to write it all to CD or DVD in just a few clicks.

However, I have just read an article by someone who suddenly found that his DVDs no longer worked, he could not read the data on them!

He decided that the most likely cause was faulty media. I must admit that I have had a similar problem - a couple of recent batches on CDR disks had problems on the innermost tracks. I discovered this when I found that music CDs I had made to play in the car often had problems on the first tracks. These CDRs were well known branded types - I must admit that they were quite cheap to buy, but I am not going to tell you which ones! Suffice it to say that switching to other cheap brands cured my problems. CDRs are really quite flimsy things, I wedged a couple under the foot of my washing machine and watched the aluminium coating just peel away.

I don't keep all my disks there, I hasten to add. But it has caused me to think hard about my backups and what brand disks I should use. With CDs it's not a difficult choice, as there are plenty of good brands at reasonable prices. There are also medical and studio grade CDR & DVD types which may be more reliable, but I've not seen these in the shops, or found them offered by UK based dealers on the web. DVD media is still quite expensive. At the moment I save money by buying slower versions - you can find these at about half the cost of the current fast disks, but who knows how reliable they are?

The author of the article wrote that he had decided to back up everything twice, using different media brands, and revert to CD which seemed more robust that the dodgy DVD-RAM disks he had the problems with. I am currently trying to rotate ten CD-RW disks for my weekly backup, which means that once a file is 10 weeks old, I will always have copies on 10 different disks. And I suppose every 10 weeks I could make an additional copy on a top branded CDR, to keep for eternity.

The stuff I write to DVD is kept in a single directory on my hard disk. This gets added to now and then, and when it gets too big to fit onto a single DVD I suppose I shall prune it - the older stuff is written to several disks already. What I shall have to do is monitor the disks for deterioration. If these disks really do fail after a while, it might not be a bad move to replace them every few years. I have a few CDs that I wrote perhaps over 5 years ago. So if there really are any that I don't want to lose, I think I shall write them to hard disk and then produce new CD or DVDs.

Of course when I die someone will chuck the whole lot in the dustbin.

WSH?

A while ago I produced some locator software for various Psion computers, and at someones request I started to write some Windows versions too. I didn't really get very far, and was distracted by other things, such as the thought of running the stuff in a browser window. These actually exists on http://www.carabus.co.uk where you can find versions for standard computers and for PDAs that have browsers that support Javascript.

I've often bemoaned the lack of a programming language on Windows computers. With my Psion it has always been easy to knock up a short program to solve some problem that was bugging me, but on my Windows PC it didn't seem so easy without additional software. Back in the days of DOS, and in the early days of Windows, there was GWBasic and QBasic provided as standard, but these didn't really fit into Windows so I didn't bother. However, after messing with Javascript running in my browser, I wondered if it would run outside. I had seen odd little configuration files with the extension .js, so what runs them?

I was surprised to discover that a standard built in program called Windows Scripting Host (WSH) does the job. As supplied in Windows 2000 and XP, it already understands Javascript and VBScript. And there are plugins to allow WSH to run Python, Perl, and numerous other script languages. (WSH does not come with Windows 98, but is available as a download).

This scripting facility is really intended for jobs such as program installations, startup configuration, and other stuff that corporate system administrators might want to do on networked computers. But the languages are rich enough for a wide variety of tasks, and provided the requirement for user interfaces is not too complicated, there are possibilities for more general use.

VBScript has only two native graphic interfaces, InputBox and MsgBox. The former allows a single item of data to be typed in, and the latter can present results and present a choice of buttons to press. And of course it can read several parameters passed to a script on a command line, if you like that sort of thing.

JScript (Microsofts version of Javascript) is even more limiting - it has no means of inputting data! Fortunately it is easy to get it to run a VBScript function (in the same file) to provide an input dialog.

Javascript was intended as a safe language to use over the internet, so no means was provided for it to play with files, change settings, or run programs. However VBScript was not designed with safety in mind, hence its usefulness for doing such things. In fact it can manipulate many Windows objects. And to an extent, any script language can be extended to do such things. For example, the Javascript accompanying this article calls a standard Windows popup dialog rather that the Javascript version.

To demonstrate its usefulness, I have written a simple locator distance calculator. Click here to download both a Javascript and VBS version. As you can see below, these are just simple text files. WSH treats a .vbs file as VBScript, and a .js file as Javascript. The .wsf file is a special case - it contains both types of script, in this case it uses VBScript only to display the input dialogs, and Javascript to do the calculations.

' VBS locator distance calculator
Dim loca(6)

title = "Locator Distance Calculator"
loc1 = InputBox("Enter locator 1",Title,"")
if (loc1 = null or loc1 = "") then
  WScript.Quit()
End if
loc2 = InputBox("Enter locator 2",Title,"")
if (loc2 = null or loc2 = "") then
  WScript.Quit()
End if
loc1 = Ucase(loc1)
loc2 = Ucase(loc2)
loc2vals(loc1)
lat1 = getlat(loca)
lon1 = getlon(loca)
loc2vals(loc2)
lat2 = getlat(loca)
lon2 = getlon(loca)
dist = calcdist(lat1, lon1, lat2, lon2)
result = MsgBox("Distance between " & loc1 & " and " & loc2 & " is " & dist & "kM.")

Function loc2vals(locator)
  For i = 1 to 6
    loca(i) = Asc(Mid(locator,i,1))-65 
  Next
  loca(3) = loca(3) + 17
  loca(4) = loca(4) + 17
End Function

Function getlat(locvals)
  lat = (loca(2) * 10 + loca(4) + loca(6) / 24 - 90 + 1 / 48) * (3.1415926/180)
  getlat = lat
End Function

Function getlon(locvals)
  lon = (loca(1) * 20 + loca(3) * 2 + loca(5) / 12 - 180 + 1 / 24) * (3.1415926/180)
  getlon = lon
End Function

Function Calcdist(lat1, lon1, lat2, lon2)
  d = acos(sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(lon1 - lon2))
  gc_dm = ((180/3.1415926) * d * 1.852) * 60
  Calcdist = round(gc_dm, 1)
End Function

Function acos(X)
  acos = Atn(-X / Sqr(-X * X + 1)) + 2 * Atn(1)
End Function
' End of script

What use WSH will be to a radio amateur, I can't really say. It might be useful for analysing logbook files - it would be quite easy to read the files and generate a report detailing the sort of stuff the logbook applications cannot handle. But it's interesting; I think so anyway.

Some recent contacts

Just to show that I do sometimes use my radio, here are a fw QSL cards recently received. All VHF of course, dunno why I did the Morse.

EA7RZ was a nice one on two metres. I had just switched on and tuned around and heard a few of the UK big guns calling someone. I dropped in my callsign, and was surprised to get an immediate 59 report. Especially as I had only a small vertical connected at the time, and was using lowish power. It just goes to show that sporadic E skywave signals can be worked on any power and aerial if you just happen to be in the right place! I liked his locator too - mine is IO91RM, his was JO91RM.

OY/DF2SS - I've worked several stations in the Faroes on Six. This one is situated in the red bus! Never heard the Faroes on two metres yet. EI3IX was my first Irish contact on six metres. We were both using FT100's feeding verticals.

EH7DLD in Cordoba, and IV3LNQ in Trieste were the most colourful cards from many contacts around the Med on six metres.

The six metre E's season should be starting soon, so I must put up an aerial again. There's no chance of sticking up the beam this year, but the mobile whip gets plenty of European stuff, so that's what it will have to be. I may be able to set up portable stations later this year, so with any luck I will be able to fill the gaps. The Greeks in particular have eluded me, although I have worked Cyprus on six so there ought not to be any problem.

For any of you M3 folk, all this sort of stuff should be easily workable on six from an FT817 or similar, and a vertical or dipole, during the early summer months. When I started on six in the late eighties, I worked stations in the USA on two and a half watts, although it was a wonderful season back then. Some days there were SSB stations in the US and Canada, wall to wall, all up to 50.5MHz calling the UK, which was the first European country to get a six metre allocation.

This summer it will not be so easy to work the Americans, but you never know - there could be a few short openings, and if you don't listen you won't work anyone. But there should be plenty of European stations around.