Wireless Waffle - A whole spectrum of radio related rubbish
48 metre Bandanasignal strength
Wednesday 16 May, 2007, 14:14 - Pirate/Clandestine
anorakThere's a term used in the UK which takes its roots from an overgarment worn by many to keep dry on particularly squally days. The aforementioned garment is an 'Anorak', which is a kind of winter jacket which, no matter what you wear it with, will never look fashionable (the possible exception being Paddington Bear who at least looked cute, though it could be argued that Paddington wore a Duffle Coat rather than an Anorak if we're being pernickety). The Anorak is generally rather unpopular, being an ugly but practical kind of a coat; but due to the fact that it is a rather warm item to wear, those who spend a lot of time outdoors but do no exercise and thus are in need of something to stop them freezing whilst standing around have taken the Anorak to heart as their overcoat of choice.

But who, I hear you ask, would want to spend all day standing around doing nothing especially if it was cold or raining? A very good question! The Anorak became (and to some extent still is) the de facto uniform of those with hobbies such as train, bus or plane spotting, collecting number plates, "Oooh, V355LOX, a rare one from the OX series when they misprinted the 5 so that it looks like an S and it reads 'V35 SLOX'", watching grass grow, and so on... In the UK, however, the term 'Anorak' has come to be associated with anyone whose hobby is just a little bit weird, sits in a niche so small that only a handful of people understand it, is a touch excentric or is just very, very dull. And thus, most avid radio listeners, especially short wave listeners, DXers and even radio amateurs are regularly tarred with the Anorak moniker.

48mbtxWhy is this of much (if any) interest? Well the picture on the right (click it to see it in its full glory), which is a rather splendid example of a clandestine pirate radio transmitter, designed to transmit music programmes on short wave, brought me to thinking about why the stalwarts who built and operated such things continued to do so. I can think of 2000 or more salient reasons why it's no longer such a good idea:

1. No one (except Anoraks - see above) listens to short wave any more.
2. In most locations, the amount of background noise from computers, electrical equipment and the like makes short wave reception virtually impossible.
3. That aside, short wave reception does not lend itself to listening to music due to the annoying fading in and out.
4. If you want people to hear your radio presenting skills, there are easier and cheaper way of doing it - just upload a programme onto the internet.
5. There are 15,000 better things to do with your time (like collecting number plates for example).
6. If you get caught, the fines can be large (GBP2,000 plus 6 months in gaol).
7. And so on...

So why do the operators stations such as AlfaLima and WR International continue to spending their hard earnt cash and wasting their weekends building, setting up and operating such equipment. I would venture to suggest that there's still a real buzz associated with doing so. For a start, it's illegal, and flouting the law often gets the adrenalin flowing (not that I'd know of course). Then there's the kudos you get by being received by other short wave anoraks, 'Radio Flump was sounding hot last Sunday morning - SINPO 32232 - Best signal yet - I could almost make out what DJ Bobbisox was saying'. Also there's a little bit of exhibitionism and showing off in it, and that too provides an ego boost all of its own.

I argue, therefore, that the real anoraks are those people who tune into and listen to such short wave pirate broadcasts but make no attempt to join in the real fun and build a transmitter and get on air with the pioneers, pirates and thrillseekers who supply their fun to start with. So instead of tuning around the band, get your soldering iron out and build a Grenade or a Corsair, record a rubbish radio programme full of music that you think is cool but everyone else has forgotten, find a remote location, set up a transmitter early on a Sunday morning instead of lying in bed a couple of hours longer. And in the process... throw away your anorak and replace it with a skull and crossbones headscarf instead.
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Wire-More LAN (Part IV)signal strength
Friday 27 April, 2007, 14:51 - Radio Randomness
Another train journey, another chance to run good ole Netstumbler and do a survey of channel occupancy for 2.4 GHz (that's 802.11b, g and n and not 802.11a in case you were wondering) to see whether my previous analysis of which are the best WiFi channels to use still holds.

For those who haven't (or can't be bothered to) read my previous article, I came to the conclusion that if you lived in an area of high WiFi penetration, channel 1 was the best channel to use as it was the least likely to suffer interference from other Wireless LAN users. In areas where there was unlikely to be any other wireless LAN activity, channel 11 (or 12, or 13) would be best, as these are the most free from other interferers (e.g. the military, microwave ovens, radio amateurs and so forth).

wifiscan1

So what are the results of this train journey? I've plotted them above. I've shown the outbound journey separate from my return journey. As it's highly possible that if I picked up a LAN in one direction, I might have equally picked it up in the other, I've filtered the return numbers to take account of this. Also, I kind of half forgot to switch my system on on the outbound journey so, as you can see, the results for the return journey show many more LAN's than the outbound!

The upshot remains exactly the same as before (phew!) Channel 1 continues to be the best channel to use if you are in an area saturated with other users. Remember when looking at the above graph that channels 2 to 5 interfere with channel 1 and as such are not independent - equally they interfere wich channel 6 - only channels 1, 6 and 11 (or 1, 7 and 13) are actually free from interference from each other. My arguments about channel 11, 12 or 13 being the best to use in quiet areas remain unchallenged.

As a postscript, I though you might enjoy one or two of the network SSID's (names) that I found during my journey. Here are my favourites:

ideal cleaning wireless'Bleach2006'
'bombolong'
'GARY BARLOW' (was it really...?!)
'Ideal Cleaning Wireless'
'legal loonies'
'SLAPHEADS NETWORK'
'supermonkey
'the wardrobe'
'TOAST'
':)'

and my absolute favourite: 'FRAUDULENT'...! Also, a few other vaguely interesting facts and figures:

Number of networks called 'BTVOYAGER': 12
Number of networks called 'BTHomeHub': 45
Number of networks called 'SKYxxxxx' (where xxxxx is a 5 digit number): 30
Number of networks called 'Belkin54g': 10 (and 7 of them were open)
Number of networks called 'default': 5 (all of them open)
Number of networks called 'linksys': 10 (4 of them were open)
Number of networks called 'NETGEAR': 16 (10 of them were open)
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A Noisy Transatlantic Oystersignal strength
Monday 23 April, 2007, 15:16 - Amateur Radio
annoyedoysterIn a previous post I discussed the fact that the powers that be in Europe had taken a decision with respect to low power, licence exempt radio equipment that meant that the 'heart' of the 70 centimetres amateur radio band had been ripped out due to a mountain of noisy interference produced by wireless doorbells, weather stations and so on.

But that's not the end of the story, or so it would seem. Not content with annoying noisy oysters by wiping out 433.500 MHz (the EU 70cms FM calling channel) as well as the repeater input and output frequencies in the UK (as well as Finland, Slovenia and certain other countries) from 433.000 to 433.375 paired with 434.600 to 434.975 MHz, I recently discovered that they have also managed to pull the wool over our eyes with respect to another travesty against 70 cms radio amateurs. But this time, it's not those of us in Europe that are suffering, it is amateurs in the USA and in particular, in areas where European tourists congregate.

What would be the worst possible frequency to interfere with? Probably the calling frequencies which in Europe are 433.500 for FM (already messed up with the aforementioned low power devices) and 432.200 for SSB. But hang on... US amateurs have a wider 70cm allocation, from 420 to 450 MHz and... their FM calling frequency is 446.000 MHz. So what type of wool have the ERO pulled over the eyes of US amateurs then? PMR 446 of course! Yes, this low power (half a Watt) licence exempt walkie-talkie technology runs on frequencies from 446.000 to 446.100 (and recently extended to 446.200 for digital modulation) - slap bang in the middle of the US 70 cms FM calling and working channels.

woolpulledNow obviously, there's little, or no chance, of UHF signals propagating from Europe to the US, so the likelihood of European PMR 446 equipment causing a problem to American amateurs is nil isn't it? Well, if the equipment is used in Europe there is no chance of interference. However, if it's taken to the US by European holidaymakers to allow them to keep in touch with each other whilst on the beach, at a theme park, or even whilst lost amongst the endless miles of aisles at Wal*Mart, then yes! And this is just what is happening. Europeans, blissfully unaware that their equipment is operating illegally once taken outside the EU, are using PMR 446 equipment in the USA (and Canada) and, in the process, producing endless interference on the main FM channels.

Somewhere in the basement of the ERO, CEPT or similar, someone is having jolly good fun thinking up increasingly intricate wheezes for messing up the 70 cms amateur bands. What next? How's about sharing the band with a very high powered radar that wipes out reception across most of Northern Europe? Oh, I forgot, they've already done this haven't they...!
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How accurate are computer coverage predictions?signal strength
Tuesday 17 April, 2007, 15:58 - Amateur Radio
Posted by Administrator
gp3These days, a lot of radio planning (broadcasting and cellular for example) relies heavily on the ability to use computers to predict coverage from a site. So Wireless Waffle thought it would prove an interesting exercise to do some coverage predictions from a known radio station and compare them with actual reception. It's probably worth adding that using a single receive antenna in a fixed location for comparison isn't necessarily fair - reflections could mean that there are strong nulls in a particular direction, though with the antenna mounted nice and high and above most nearby obstacles these effects are minimised.

The prediction tool used is RadioMobile, which is a freeware tool designed for radio amateurs and does pretty good VHF and UHF predictions as well as path profiles which can be used to hazard a guess at microwave links too. The 70 centimetre amateur band was used as the test case and the signals from various neighbouring repeaters as the benchmark. Most repeaters have decently sited antennas at a reasonable height and free of local obstructions and so should make for a reasonably accurate prediction.

First off, a scan around the 70cm (433 MHz) band on a day when propagation is flat was conducted, to see which repeaters could be heard and what strength they were. Here's the list (channels not listed are ones on which nothing was heard):

RB0 GB3BN S9+ (Bracknell)
RB1 GB3BV S3 (Hemel Hempstead)
RB2 GB3LV S1 (Ealing)
RB3 GB3HL S9+ (Hillingdon)

RB6 GB3LW S3 (Central London)
RB7 GB3HZ S9+ (Amersham)

RB12 GB3GF S9+ (Guildford)
RB13 GB3VH S3 (Welwyn Garden City)
RB14 GB3HR S9+ (Harrow)
RB15 GB3FN S9+ (Farnham)

70cmrepeatermapSo the question is, could a computer prediction reproduce this set of results? The parameters of the station plus those of all the nearby repeaters (including those that are nearby but which weren't received) were entered into RadioMobile and a plot produced. The results are shown on the right (click to see the full size version).

The easiest way to see what the results show is to look at the colour of the line between the amateur station used and the various repeaters. A solid red line indicates that the prediction shows there to be no possibility of a signal getting through; yellow indicates that reception would be on the fringes of possibility and green indicates that all should be OK. A dotted line shows that the prediction is borderline between two possible outcomes. So here's what the prediction says (ignoring all those which are purely red and thus should be inaudible):

RB0 GB3BN Green
RB1 GB3BV Dotted Red
RB2 GB3LV Dotted Green
RB3 GB3HL Green
RB4 GB3NK Dotted Green

RB6 GB3LW Green
RB6 GB3DI Dotted Red
RB7 GB3Hz Green

RB11 GB3HN Dotted Green
RB12 GB3GF Green
RB13 GB3VH Green
RB13 GB3ET Dotted Yellow
RB14 GB3HR Green
RB15 GB3FN Green

A number of predictions have been highlighted in bold as these are at variance with what was borne out in practice. It seems there are 4 other repeaters which should be audible that aren't. Also, GB3BV is shown as very marginal on the prediction yet is a reasonably good signal. However, the prediction has correctly identified approximately the correct likelihood of reception for 9 of the original 10 repeaters being received.

So are predictions any good? From the results shown here, they're not bad, however the relatively simple predictions produced by RadioMobile are probably insufficiently complex to take account of other factors that play a major role in radio propagation such as clutter from trees and buildings. Nonetheless, not a bad result and an interesting illustration of the power of computers.
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