Beechlog
The on-line magazine of the
Burnham Beeches Radio Club.
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Beechlog
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The on-line magazine of the
Burnham Beeches Radio Club.
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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.
Club web address
More keyboards
Illustrating Beechlog
Dodgy disks and washing machines
WSH?
Some recent contacts
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)!
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!
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.
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| 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!
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.
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.
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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.
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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. |
BeechLog is Copyright Burnham Beeches Radio Club 2004.
Copyright of individual articles and pictures remains with the
authors.
Any opinions inside this issue of BeechLog are those of the
authors, and must not be assumed to be also of the BBRC.
Roger GØHZK, Editor