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November 2003

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

Welcome to the November edition of BeechLog.

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...

Roger GØHZK, Editor

Contents

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

Routing around the house

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.

More on DAB, a follow up to Johns demonstration

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.

Ground Planes

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.

Email on a prickly bush

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.

Blackberry 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.

incoming mail

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.

compose 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!

Teaching new amateurs

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.

Useful Links

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.