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Welcome to the on-line magazine of the Burnham Beeches Radio Club.
Published whenever I find time to do so, this is the November 2003 issue. |
Hello to all of you. This month I've actually managed to get Beechlog out
in the right month, so I hope that there's something to interest you inside.
A welcome to anyone who has stumbled upon this issue. In the past I've
had emails from people far away, since all this lot is indexed in various
search engines. I don't put meta-tags in the xhtml, but it still gets
read by various robots! Thinking about it, most of those links will
now be dead, as Beechlog has moved domain, but no doubt it will be picked
up in time.
This issue is mainly text, with few pictures. Some of the articles are not
easy to illustrate. But that'll make it easier to read the mag on your phone,
or whatever people use these days.
I've not been along to the club for a while now. This is because I work
shifts, so if I'm not there, you can bet that I'm slaving away repairing
some part from an airliner. I don't expect to get along before the new year,
although I might have a day off work on a club night - I've still got 35.5
days left for this financial year (October-October). I don't mind the shifts,
although getting up at 5.30 is not exactly enjoyable, especially when it's
dark and frosty. The other shift means leaving work at 10pm (usually club
nights) but at least the traffic is fairly quiet at that time.
So if I don't see you, a very happy Christmas to you all (and a happy holiday
to Mark). Honest, these Yanks...
Routing around the house
More on DAB, a follow up to Johns demonstration
Ground Planes, a few thoughts on cheap verticals
Email on a prickly bush
Teaching new amateurs, do we have a problem?
Useful Links
Looking through the last RadCom, I find it rather depressing that there seems
to be nothing new and modern in the way we make our radios and modulate our
transmissions. OK then, I know that there are a few recent newish digital
modes, but as far as the radios are concerned there is next to no technology
to accomodate them. And where is the successor to ssb?
Comparing radios to computery devices, there is no contest. Equipment in the
computer world has a market life of about 3 months, and there's always
something new around the corner. Performance is always on the increase,
whereas our radios performance doesn't seem to have changed much since the
FT101.
Some computer things have been around for years, starting out as hugely
expensive corporate gear, but slowly reduce in size and price 'till they
become domestic items. I've recently obtained such a device, in an attempt to
solve the problem of my offspring spending all their time using my computer
on the internet.
In my household we don't have anything like DSL (no BT line), cable modems
(no service in Slough) or heaven forbid PLT. So here the dial-up modem still
reigns. The first problem was solved by getting a second telephone line, so
all I needed to do was to work out a way of sharing this, especially with a
son who spends all evening using MSN Messenger.
After a few other ideas, I decided to look out for an old dialup router.
These things were once used by businesses who didn't have a permanent
internet connection, and they enabled any networked user to dial up when they
wanted to fetch email or connect to their head office network.
Today there are a number of routers designed for use with broadband modems.
Although not publicised, some of these still support dial-up, and I found one
of these locally. It's a USR Broadband Router, and features an RS232 port to
which a standard modem can be connected.
The router is a pretty basic unit, costing around £40. Besides the serial
port there is a 10/100 Mbit/s ethernet connection for a broadband modem, and
four 10/100 Mbit/s ethernet connections for PC's on your LAN. There is also a
printer port.
The router contains a few elements to make setting up a home network easy and
safe. There is a DHCP server, so you need only to set your PCs IP address to
automatic, and the router assigns their addresses when they are switched on.
Although there are only four ethernet ports, you can connect additional hubs
to supply up to 254 computers.
Like most routers, Network Address Translation is used. This means that your
computers are invisible to other users on the net, who can communicate only
with the router. This makes it difficult for anyone to hack into your
computer and deposit a worm or virus. You can also place restrictions on
outgoing data. As with other firewalls, you can open up specified ports for
special applications, route them to specific computers, or even have a
completely open path to a specific machine.
Setting up this box was simplicity itself. I plugged the modem into the
serial port, and my computers into the the ethernet ports. Then I typed the
router IP address into a browser, and up came the router configuration pages.
All I had to do was to select dial-up via the modem, and enter the usual isp
details, and that was it.
With this setup, whenever anyone tries to access the net, the router dials it
up and connects them, if it's not already connected. So problem solved. Of
course, things are never quite so simple. I had all sorts of strange things
happening at first, mainly due to the inexpert way I had made up the cables.
I have a crimping tool, provided by some former employer who disposed of my
services, so I made up all my leads. This is not quite as simple as it seems,
you have to somehow straighten half an inch of the cable inners, cut them all
to the same length, and cram them into the plug, making sure that all 8 wires
go all the way into their correct holes. If each twisted pair went
side-by-side, this would be less of a problem, but of course the clever dick
who designed these connections was a bit sadistic!
Anyway, I've now got ethernet cables running up my outside walls, probably
radiating all over the amateur bands, and acting as a magnet for lightning.
All par for the couse, I suppose.
Those of you attending on 1st September would have seen a demonstration of the Psion
Wavefinder device attached to my laptop. The format of my talk was more of a "show
and tell" style rather than a technical dissertation, which to my surprise actually took as
long if not longer than I thought it would. I would like the chance here to go over again
the main points and speculate as to where this all could be leading us.
The concept of the Psion Wavefinder appears to be that you are provided with a box
capable of wideband reception of a spectrum of frequencies between 189 and 240MHz,
with a few additional frequencies around the 1.4GHz area. In London there are DAB
transmissions coming out on 5 specific spot frequencies, each known as a multiplex.
Each multiplex is allowed to send data at a speed of 1.2MBps. So the Psion is capable of
receiving all of this simultaneously then sending its output in bulk to the input of a PC.
This is where the software comes in.This is where the software comes in.This is where the
software comes in.
The CD ROM sent with the Wavefinder has as you saw its problems. This forced me to
look around on the Internet and after some extended checking I found some third party
software which seems to do a reasonable job of signal processing. Currently there is
WINDAB and also DAB BAR. I have selected DAB BAR which is shareware and
presently at Issue 1.3a.
DAB BAR permits not simply reception of the audio transmissions themselves, but also
on a PC their recording on a timed basis via another related programme called the EPG
EXPLORER. This is an electronic programme guide detailing all programmes, their
timings, plus specific programme information over a 7 day period for 17 stations
extracted from the main station list of DAB BAR. The data for the EPG EXPLORER is
carried in data streams running alongside the main station transmission data. It is
possible to select a specific station on a specific day, then a specific programme for
recording in MP2 format. In order to keep the 7 day programme information up to date
one has to run a daily file update in order to maintain the capability of seeing programme
information for the next 7 days.
Additional to the above, DAB BAR also includes a third routine called the BWS
EXPLORER. This decodes another data stream to produce a visual output in web page
format. The one shown to effect was BBC VISION RADIO, a web style page containing
up to date news, business, weather, sport, and travel information in text format.
DAB BAR will function on its own as a stand alone programme, either with or without
the EPG EXPLORER and BWS EXPLORER, however it is clear that these provide
additional functionality over and above a conventional radio, or even a conventional
DAB radio. If like me you have the misfortune to be saddled with a 56k dial up modem
and you want to listen to the radio whilst surfing or word processing (I'm doing this right
now!), this appears to be a good solution, as the Wavefinder forms part of an Intranet
providing separately processed data direct to the PC The main disadvantage is that it is
only as portable as one is prepared to be when carrying around a laptop with this plug in
antenna box!
New chipsets now enable DAB receivers to be ever smaller, however these new receivers
don't all use the full spectrum of capability of the transmitted data within the DAB
transmission format. So heres where we get the crystal ball out to forecast future
developments. It is possible now to get a mobile phone which receives FM radio. It is
also possible to get a mobile phone with a full colour built in PDA. So its not a giant leap
of imagination to see these all combined but with DAB, and perhaps a docking unit
capable of recharging and delivering output either to speakers or an amplifier in a fixed
household situation.
For this to happen there must be manufacturers with foresight out there, and there has to
be further enhancements to the interactivity and usablity of DAB as it is presently
constituted.
For references see:
http://www.psion.com/infomedia
http://www.wavefinder.co.uk
http://www.windab.co.uk
http://www.dabbar.co.uk
http://www.ukdigitalradio.co.uk
http://www.bbc.co.uk/dab
John Kipping G0GCL © 16th September E&OE All rights reserved.
I've been thinking about HF aerials recently. I do quite a bit of this sort
of thing. Thinking I am good at, it's putting my thoughts into practice that
causes me trouble.
When setting up an HF station, after getting the radio equipment, we then
think about aerials. Of course, we should really do it the other way round,
but in the real world this rarely happens. So we then turn to the aerial
adverts to see what's available. Then we find out that commercial aerials are
pretty expensive, and there's little left over after buying the radio, so
what can we make?
A while ago I wrote about dipoles, especially their capabilities on more than
one band. Now if you have been on a Foundation course recently, you will have
learned that there is another fundamental type of aerial, the quarter wave
ground plane. I am sure you all know this, after all we stick one up at
Farnham Common Village Hall now and then.
But ground planes are often forgotten by amateurs, possibly because there is
a bit of folklore about them being single band and difficult. Well I suppose
that if you don't want to use an atu, there's some truth in this. But in
reality they can be just as versatile as dipoles, and not really a great
problem to build.
My first ground plane was a 2 metre model. I took a BNC chassis mounting
socket, and made the vertical element out of a thin strip of aluminium I
found in the scrap metal bin at work. Two other strips formed the two radials.
Connecting these to my transmitter via an SWR meter, I tuned the thing by
bending the radials at a suitable angle to get a good match. The whole
assembly was then hung up in the loft at my flat in Slough, where it probably
still is.
Now you can't make an 80 metre ground plane the same way, I grant you, the 20
metre bits of metal would never fit in the scrap bin. But there are other
methods. You can make a nice, resonant, ground plane on any band between 10
and 20 metres by modifying a CB half-wave aerial. These consist of about five
to six metres of aluminium tubing, with a transformer built into the base.
So all you need to do is to adjust the length of the radiator, by sliding the
tubes inside each other, or removing some. Then disconnect the transformer -
you may have to drill out the rivets that hold the thing together to do this.
Then connect the centre pin of the connector to the base of the aerial.
Radials can then be added at whatever angle fits your installation. You only
need two to four quarter wave bits of wire.
On the lower bands different techniques are required. You may be able to
lengthen the CB aerial to resonate on 10MHz, but for 40 metres it's probably
best to use telescopic glass fibre rods, rather like the aerial you've seen
at the club. 80 metres and top band are really stretching things, but you
can always bend your ground plane into an inverted L. It might end up with
the L turned 90 degrees, with the horizontal bit longer than the vertical,
but it's worth trying. You can also try a quarter wave sloper, say a resonant
wire strething from a pole on the chimney to the bottom of the garden.
It is possible to use a ground plane on more than one band, with the aid of
an atu. The trick, as with dipoles, is to make sure you don't get a really
high impedance on one of the bands. So increase or decrease the lengths by
about 10% over the calculated length. You probably won't get perfection on
too many bands, but you may well get as good or better results than many
expensive commercial aerials.
If you use an atu, don't worry too much about exact lengths. A variation of,
say, 1 metre on a 40 metre ground plane will not make a great deal of
difference to its radio performance, provided you match it properly to your
radio.
The more adventurous of you might like to try bottom loading a CB or glass
fibre vertical for 80 or 160. You've probably seen the immaculate commercial
versions, with nicely integrated loading coils, but you needn't worry about
trying to get a similar effect. Just make up a tapped coil wound on a bit of
plastic drainpipe, and experiment to see which tap works the best. This coil
doesn't have to be mounted nicely in line, it can just dangle off the bottom
af the aluminium tubing. You can probably find some useful inductance values
on the web or in an aerial book, but if you can't, don't worry. These CB
verticals are also strong enough to support a 'top hat', more room for
experimentation.
As with all aerials, the higher you mount your construction, the
better, especially on the higher frequencies. It's easier to raise up modified
CB aerials than glass fibre types, but take into account how you are going
to secure the radials. And if you want to use it on more than one band, you
could try two radials cut for each band, although I'm not convinced that this
is worthwhile.
Anyway, these aerials should be cheap. Glass fibre poles don't cost much, nor
do CB half-waves. I suppose you have to add the cost of an atu, but you could
make this also, although big variable capacitors for manual atus are probably
difficult to get hold of these days. A look at the medievel valve junk at any
rally might reveal suitable components though.
It's been a few years since I dismantled my packet station. When packet was
new, I had visions of an automatic method of receiving and sending messages
to anywhere in the world. Well this happened to a degree, although rather
slowly. I was able to send and receive them from Johns BBS quite easily.
I dreamt of a totally portable solution, and had all the parts working, my
Psion, a low power consumption TNC, and a handheld radio. However there were
a few frustrations. I never managed to achieve automatic receipt and delivery
of messages, although this facility was built into my tnc. The problem was
something to do with the interface between the tnc and the BBS, which
corrupted my address and prevented mail reaching me.
But the main problem was that I always had to connect to the same BBS to
retrieve mail. This is fine for a fixed station, but no good if you are on
the move - the white pages directory gets screwed up.
So it is interesting to see that at long last there is a solution to this
problem, although it doesn't involve amateur radio. The answer uses packet
radio, and is called Blackberry.
Blackberry is a device that will fit in my shirt pocket. It runs for nearly
two weeks without recharging. And the messages are standard internet email.
So how does it do this?
Blackberry is a gsm phome-cum-pda, but with a difference. It's rather like the
old BBS system, except that the BBS is connected to the internet somewhere.
The phone links to the 'BBS' using gprs. Whenever I wish to send an email, I
type it in and press send. A gprs link is automatically made to this server,
and the message transferred to the internet email network. Receiving email
requires no effort. When the server receives an incoming message for me, it
initiates the link and transfers the email directly to my device.
Initially the Blackberry is set up with its own email address. This is useful
in itself, but in addition you can receive mail from most standard internet
mailboxes, even including Hotmail and Aol. This is pretty simple too, you
just tell the device your mailbox address and login details, and these are
passed to the server. The server checks each nominated mailbox for new mail
every so often, and when it finds a new mail it is transferred to you.
Of course there are many gsm phones that can do email. The difference is that
the Blackberry user does not have to initiate any kind of connection, it just
happens automatically. Since the server pushes email to your device only when
it is available, there is no battery power wasted in checking for new mail.
The power management is quite amazing. The device uses very low power -
compare this to any modern pda where you are lucky if it lasts a few hours
when powered up. When a message is received, only the first 2k of message is
transferred to the phone. This is enough for most emails, but if the mail is
bigger, more is transferred from the server as you page down the screen. This
prevents the phone from getting clogged up with large spam and virus-laden
messages, and keeps the power consumption down. You can save emails to a
protected folder on your device, otherwise when the memory fills up, the
oldest emails are overwritten.
The server, like a BBS, holds copies of all the mail it receives from the
various mailboxes. You can also access these via a web interface using any
computer. More importantly, in these days of prolific spam, you can set up
filters which decide what mail to send to your device. For example, I have
set mine to send me mail addressed only to my various email addresses (spammers
often effectively address the 'envelope' that accompanies the spam, so your
address doesn't appear on the stuff you receive). This
eliminates all the spam that does not contain my address in the header, which
accounts for most of it. I then set filters to allow stuff from various
mailing lists. Another filter detects mail to an early form of my main email
address, which is only used by spammers. I've also set a "timeout" on the web
client inbox, so that messages of a certain age are deleted after a few days.
The Blackberry also has a few other applications, like a simple web browser.
I'm certainly able to google using this, and the various low text news
services work well. There is also a diary - for corporate use this can be
synchronised via gprs with the company copy, which can be Lotus Notes,
MS Exchange, etc. There's a sort of instant messager too, as you can send
messages directly to any other Blackberry (via gprs), provided you know the ID
number. And of course you can use it as a phone, and send and receive sms
messages.
It's interesting to note that the manufacturers have made agreements with
companies such as Palm and Nokia, so this technology may well appear
elsewhere.
Thinking back to where I started, most of the problems with the old packet
BBS systems could have been solved simply by linking each packet BBS to the
internet, probably using a virtual private network. So you could connect to
any BBS, and the white pages could easily detect your home BBS, and log you
on to it, however remote you are. Such a network which would use the
internet, but be isolated from it, should be acceptible to the RA.
A small step forward would allow us to send and receive email via packet
radio, although with the current level and nature of spam, it might be
difficult to persuade the RA!
Like some of you. I reularly read the postings in the usenet newsgroup
uk.amateur.radio. Generally speaking, this group is dominated by a
few self-opinionated individuals, whose views are often absurd.
However sometimes reading alternative views can be enlightening, and
in one case I have some agreement.
Several people have commented on the difficulty of finding a Foundation
Course within reasonable travelling distance. One might think that the
RSGB web pages on these courses would be a good guide to availablilty, but
in practice this is not the case. It's probably because this is a low priority
job at RSGB HQ, or that the person responsible has too many other things to
do.
To get round this problem, it has been suggested that the course could change
to a mainly on-line activity, where all training and the exam are conducted
via web pages. Personally I don't agree, because I feel that this just adds
another complication to the business, such as the provision of internet
terminals and prevention of cheating.
However, there certainly is a problem. Training Foundation students is not arduous,
for they are normally willing, interested students. But the rigmarole of setting
up a course, the paperwork, rooms, finding a free weekend for all the course
teachers, and so on, tends to be a stumbling block. And as far as a potential student
is concerned, finding a course is not as easy as it ought to be.
Improving the RSGB web site would be very helpful. There currently is too little
information. What I think we need is a Geoff Watts (prefix lists) type character
who would take on this job as his/her sole responsibility. Ideal for the retired
amateur (which means a great many of us), this person would need to know how
to create and publish web pages, and be keen to keep in contact with all the
instructors and organisers, registered or otherwise. He/she should have no other
RSGB responsibilities, just this one job.
I really don't know how to reduce the job of course organisers. It's a fair bet
that within any club it is the same folk who organise everything. Which means
that they have to fit the course in with all their other activities. So what
may be needed is an alternative group who can organise courses. It has been
done before - the RSGB managed to organise Morse testing sessions all around
the country. Perhaps the Morse ex-testers may now have time on their hands?
I think that the RSGB ought to proactively have some of their people
chasing up folk to do this. Currently they seem to wait for people to volunteer.
People have to be persuaded to volunteer. And also I think that they need a
list of Foundation teachers and examiners who are willing to serve on a course
organised by some other club or group or individual. If each area or county
had a group of 'flying tutors', the jobs of organising and teaching would be
split.
Certainly some actions are required pretty soon if the new licence structure
is to be a success.
Info on the
USR Broadband Router.
A new way to browse the net, Stumbleupon,
enables you to find some of the most extraordinary web sites that you never
knew existed.
Rogers Locator calculators, I'm slowly
getting the bugs out, and one day should be able to refine the code a bit.
Fed up with the shortcomings of Internet Explorer? I've been using
Mozilla Firebird
as my main browser for the last couple of months. Firebirds tabbed browsing
is a delight, and the non-invasive installation (unzip into a folder) is
how these things should be.
On similar lines, Mozilla have a separate email client,
Thunderbird,
which allows relatively safe reading of html mail, has comprehensive
anti-spam filtration, simple installation, and like Firebird is free.
The BBRC
Events List.
Copyright and Technical Stuff.
BeechLog is Copyright Burnham Beeches Radio Club 2003.
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