Wireless Waffle - A whole spectrum of radio related rubbish http://www.mf2fm.com/blog/index.php http://www.mf2fm.com/blog/interface/feed.png http://www.mf2fm.com/blog/index.php Wireless Waffle - A whole spectrum of radio related rubbish Copyright 2012, Richard Womersley, G1JAJ Richard Womersley, G1JAJ en-US SPHPBLOG 0.4.8 Harmonics - Putting The Record Straight http://www.mf2fm.com/blog/index.php?entry=entry120122-210909 Wireless Waffle has tried to explain and demystify many of the more esoteric technical terms and concepts used in the wireless world such as OFDM, intermodulation and even interpreting ionograms. There is one very straightforward technical concept that is so often misused that it's time the record is set straight. That concept is harmonics.

Harmonics should be the easiest concept to understand. Passing any radio (or for that matter audio) signal through anything that is not perfectly linear (and the only things that are perfectly linear are pieces of wire) will produce differing degrees of harmonics. The non-linear device will produce other things as well (such as the aforementioned intermodulation) but harmonics are probably the number one resultant.

A harmonic is simply a copy of the original signal but with it's frequency multiplied by an integer. The second harmonic is therefore the original signal but with all it's frequencies doubled.
  • The second harmonic of 1 MHz is at 2 MHz;
  • the second harmonic of 10 MHz is at 20 MHz;
  • the second harmonic of 150 MHz is 300 MHz;
you can clearly see the pattern emerging. harmonics of deep purpleMusicians will recognise the second harmonic as being an octive. The third harmonic is simliary the original frequency, but tripled. The third harmonic of 1 MHz is 3 MHz, and so forth. The n-th harmonic is the original frequency multiplied by 'n' so the 273rd harmonic of 2 MHz is... 546 MHz. You can even play the game with light (just about) as the second harmonic of deep red (almost infra-red) is deep purple (ultra-violet) which probably explains why so many wannabe rock groups use devices such as 'harmonisers' and 'harmonic sweetners'. The only rule is that 'n' has to be an integer. There is no such thing as the 'second and a halfth' harmonic, and this seems to be where the confusion arises.

As harmonics are so common, much effort is made to ensure that transmitters are filtered to remove them. A low pass filter is one which allows lower frequencies through but attenuates higher ones and is almost universally tacked onto the output of any transmitter. You would not want a high power TV transmitter on 534 MHz (UHF channel 29 in Europe) radiating strong signals at its second harmonic frequency of 1068 MHz, in the middle of the aeronautical safety band, any more than you would want an aeronautical system at 1068 MHz radiating at 2136 MHz and causing interference to 3G base stations!

mistress harmonicSo often, you will see spurious emissions from a transmitter being called 'harmonics'. Unless those emissions are on direct multiples of the main transmitter frequency they are not harmonics, but will either be intermodulation or could be caused by the transmitter squegging. Either way, the term harmonics seems to have been awarded a new meaning to encompass all spurious emissions from a transmitter. As a Wireless Waffle reader, now that you know different, any violations of use will be punished strictly and severely.

For completeness, it is worth pointing out that there are (very rarely) such things as sub-harmonics. These occur on frequencies that are integer multiples of integer fractions of the original frequency. As an example, a problem was reported by the operator of a private mobile radio system on 72.45 MHz of breakthrough from a co-sited FM broadcast station on 96.6 MHz. 72.45 is precisely three-quarters of 96.6. This rare problem was caused by the synthesiser in the transmitter which had an oscillator on 96.6 MHz which was fed into a pre-scalar that divided the signal by 4, producing an output at 24.15 MHz. This signal was rich in harmonics and due to the shoddy design of the transmitter, the third harmonic of this signal was being fed into the transmit amplifiers and appearing at the antenna output - nasty! An additional filter on the output of the FM transmitter cured the problem. It's perhaps no surprise that the company that made the transmitter in question (who won't be identified) is no-longer manufacturing them!]]> Spectrum Management http://www.mf2fm.com/blog/index.php?entry=entry120122-210909 Richard Womersley, G1JAJ Mon, 23 Jan 2012 04:09:09 GMT http://www.mf2fm.com/blog/comments.php?y=12&m=01&entry=entry120122-210909 Russia is the Tsar of Pirates http://www.mf2fm.com/blog/index.php?entry=entry120119-073000 Wireless Waffle has talked extensively about pirate radio in the past, from short-wave music stations, to Brazilian sat-jackers. But it seems that, of all the nations on the planet, the Russians hold the baton for being the biggest pirates of them all.

This story begins when reading the latest intruder report from the IARU Region 1 Monitoring System. The report indicated that there had been an intrusion into the 80 metre amateur band between 3.5 and 3.6 MHz by Russian pirate stations running AM. Now historically the Voice of Korea (the North Korean broadcaster) has been transmitting in the 80 metre band (or the 75 metre band as it's called in in North America) on 3560 kHz in AM and the immediate assumption was that these new signals couldn't possibly be Russian pirates, but must be the Voice of Korea and perhaps a few other stations trying to jam it. The IARU report, however, says that the carriers are very unstable and that the modulation is voices in Russian.

blue soldier red squareSo the only thing to do to verify this story is to turn on a receiver and have a listen. Having done this, there were no obvious signals in the 80 metre amateur band. Having previous heard pirates just below the band at around 3450 kHz, the tuning dial was slowly rotated to ever lower frequencies. Nothing. And then, at 3175 kHz, something. A weak carrier... no, two carriers alternating... both rather unstable in frequency. Switching the receiver to AM yielded weak modulation. A bit more tuning, to 3125 kHz and a much stronger AM signal with a Russian voice and a wobbly carrier. Hey presto!

But what are these odd signals? Are they military operators in a private net (if so, why AM and why unencrypted)? Are they some kind of harmonics or intermodulation? Googling didn't bring much until a page on Sparky's Web Blog was found. It seems that these are effectively the equivalent of Russian CBers but presumably using much lower frequencies given the large distances between Russian cities. The band is known as the тройка band ('troika' in English which has several meanings from 'three of a kind' to a sledge or fairground ride). The band runs from approximately 2900 to 3200 kHz which are internationally allocated to the Aeronautical Mobile and Mobile services.

red square blue squareThere are aeronautical frequency assignments in the band (2872, 2899, 2921, 2962 and 3016 are frequencies assigned to North Atlantic traffic for example), but these lower frequencies are less often used unless propagation makes it totally necessary. Oddly, the various frequency lists for the band show very little aeronautical use in Russia (other than Irkutsk on 3016 kHz) - a coincidence? Probably the pirates know this and therefore feel free to mess about in the aviation bands, knowing that the Russian authorities are likely to be little interested in their activities.

If you're in Europe, when it gets dark (and lower frequency propagation opens up over the continent), why not give them a listen. It's fun to chase the carriers up and down in frequency. If you speak Russian, perhaps you could provide some translation as to what on earth they are talking about!

P.S. You might also want to take a listen to 2920 kHz USB as this seems to be a common calling channel for the more technically adept Russian pirates.]]> Amateur Radio, Pirate/Clandestine http://www.mf2fm.com/blog/index.php?entry=entry120119-073000 Richard Womersley, G1JAJ Thu, 19 Jan 2012 14:30:00 GMT http://www.mf2fm.com/blog/comments.php?y=12&m=01&entry=entry120119-073000 BBBBCC Rraaddiioo Ssccoottllaanndd http://www.mf2fm.com/blog/index.php?entry=entry111209-081715 Rraaddiioo Nneeddeerrllaanndd that suffer from an echo on transmissions. It was a dreich day and being concerned for relatives who live in Northern Scotland, last night the Wireless Waffle receiver was tuned to BBC Radio Scotland on 810 kHz.

jenny bbc radio scotlandThe 810 kHz service is transmitted from three stations, two high powered (Burghead and Westerglen) at 100 kW a piece, and a lower powered fill-in at Redmoss at 5 kW. From the south of England, only the two higher powered stations are audible and during the evening are pretty much at similar strengths and lo! and behold, there was an annoying echo echo on the signal.

Where multiple transmitters operate on the same frequency, it is as important that the audio feeds are synchronised as it is that the transmission frequencies are. Where both can be received at similar signal strengths, any difference in frequency between the two causes an audible heterodyne (a.k.a. whistle) to be heard. If the audio is not synchronised, an echo can be heard. Any difference in audio delay between the sites should typically be kept below a few tens of milliSeconds if the resulting echo isn't to cause a loss of intelligibility.

There are many reasons why transmitters may have audio feeds that are not synchronised. For short-wave services, the feeds may be on completely different routes. This became a bigger problem for international broadcasters when short-wave feeder transmitters were replaced by satellites. For many years, the BBC World Service maintained a 24 hour English language service on 6195 kHz (these days it is used for a variety of different languages and is shared with other broadcasters too). In those halcyon days, different transmitters around the world were used to maintain the frequency and typically sites in the UK, Middle East and Singapore would share the honours. At times, however, some of these transmitters may be on at the same time. It was not uncommon for Singapore and one of the UK sites (eg Skelton, Woofferton or Rampisham) to be transmitting English language programmes at the same time. But Singapore was fed via satellite and Rampisham by direct land-line. The result - 'The news the news read by Damien read by Damien Trellis Trellis' - over most of the world inbetween the two sites. This was eventually resolved by adding in a delay to the UK feed at Bush House to bring the networks back into alignment.

It's a shame, therefore, that BBC Scotland haven't learnt the lessons of their sassenach colleagues and got their own delays sorted out. Not least, the national DAB network has to be synchronised to within microSeconds so sorting the medium wave network out ought to be child's play.

As they say in Scotland, 'Whit's fur ye'll no go by ye!']]> http://www.mf2fm.com/blog/index.php?entry=entry111209-081715 Richard Womersley, G1JAJ Fri, 09 Dec 2011 15:17:15 GMT http://www.mf2fm.com/blog/comments.php?y=11&m=12&entry=entry111209-081715 Radio Killer - Don't Let The Music End http://www.mf2fm.com/blog/index.php?entry=entry111128-051026 Wireless Waffle we're working on something a bit special. A project that will help sufferers of broadband drop-out everywhere. Meanwhile, we thought you might like the latest offering from Romanian groovers Radio Killer, 'Don't Let The Music End' (lovers of 80's hi-fi will enjoy their web-site!)



It isn't as good as Lonely Heart which we plugged for chart success earlier in the year (and still think there's a chance it might make it some day), but it's nice to see an inventive video (ie one that isn't just scantily clad ladies a-groovin' and a-grindin'). And Radio Killer singer 'Lee Heart' has a very girl next door kind of look, which again makes a refreshing change from the 'less is less' attire of some other pop stars.

One ponderance we had was whether there was just a little plagiarism going on when they thought of the title, as it's precariously similar to 'Don't Let The Music Die' from fellow Romanian Inna...]]> Chart Predictions http://www.mf2fm.com/blog/index.php?entry=entry111128-051026 Richard Womersley, G1JAJ Mon, 28 Nov 2011 12:10:26 GMT http://www.mf2fm.com/blog/comments.php?y=11&m=11&entry=entry111128-051026 Another Radio Birthday... http://www.mf2fm.com/blog/index.php?entry=entry111017-073812 It's been a while since we discussed CB radio here at Wireless Waffle and it's not time to go over old ground now. What it is time for, is to dust of that old rig that's propping up the WiFi routers that are sitting in the corner of your garage, sort yourself out a twig, and join the birthday celebrations.

CB radio becomes 30 years old on November 2nd this year, and to commemorate this landmark, there is going to be a party called 'The Big Net'. Set your dial to Channel 30 (UK) or 27.89125 MHz if you prefer, and put out a call between 7pm and 9pm. Wouldn't it be good if the result was the discovery of a few old breakers who you had lost contact with. Or embarrassing if you happen upon a few old seat-covers! A big 10-4 on that one.

Keep the lipstick off your dipstick and the smokies off your tail, good buddies. 10-10 'til we do it again.]]> Radio Randomness http://www.mf2fm.com/blog/index.php?entry=entry111017-073812 Richard Womersley, G1JAJ Mon, 17 Oct 2011 13:38:12 GMT http://www.mf2fm.com/blog/comments.php?y=11&m=10&entry=entry111017-073812 Happy Birth-DAB Sweet Sixteen http://www.mf2fm.com/blog/index.php?entry=entry110927-050905 27th September is a good day for birthdays. Not only is it the birthday of Internet Goliath Google, but it's also the date on which DAB radio was launched in the UK.

DAB radio was launched with a fanfare in London by the BBC on 27th September 1995 - 16 years ago. At the time, only the BBC multiplex was on-air carrying the existing analogue services. They were soon joined by BBC World Service and then by a rag tag collection of new services such as 5 Live Sports Extra and 6Music. On 15 November 1999 it was joined by the first national multiplex, Digital One.

So on the 16th birthday of DAB in the UK, how far has the service progressed? The following promotional script, leaked from the BBC, advertising DAB radio, says it all...
Fed up with FM radio? Had it with top presenters and big name artists? Are quality and professionalism beginning to bore you? Is high quality sound too run of the mill? Then maybe DAB radio is for you...

Gone are the crackles of FM reception, with DAB, it's bubbles you'll be hearing. And that's if you can get anything at all. The 'digital' nature of transmission means you'll either get something, or nothing at all (and usually it's the latter).

If you're used to digital mp3 audio, then you won't not be disappointed. Our state-of-the-ark mp2, low bit-rate, audio encoding will remind you less of modern day CD audio and instead bring back nostalgia for the cassette tapes your parents used to make in the 1980s.

And unlike regular radio broadcasters, DAB stations come and go at a whim. So if you find yourself liking a channel, get ready to be disappointed when it disappears. And you won't be able to use a cheap radio - you need specialist equipment and an aerial the size of a playing field.

So if you crave a challenge, dine with disappointment, make mountains of money, have tons of time, and don't actually care about anything much, maybe DAB radio for you.

DAB radio, mono at it's best...

Kind of says it all, doesn't it?]]> http://www.mf2fm.com/blog/index.php?entry=entry110927-050905 Richard Womersley, G1JAJ Tue, 27 Sep 2011 11:09:05 GMT http://www.mf2fm.com/blog/comments.php?y=11&m=09&entry=entry110927-050905 Maximise your mobile signal http://www.mf2fm.com/blog/index.php?entry=entry110810-071940 maximising coverageOfcom has recently published a leaflet outlining how mobile subscribers can go about maximising their mobile signal with a view to getting the best possible coverage. The leaflet covers issues such as checking coverage first, before buying a phone (shops have on-line coverage checkers available), trying out different operators (by testing different SIM cards) and has a few technical measures such as the use of Femtocells (tiny mobile base stations you can install in your own home) and UMA (carrying your voice traffic over WiFi when you're in the coverage of a suitable hotspot).

This is all well and good, and reasonable advice, but it doesn't cover how you might go about getting a better signal if you are stuck in an area with poor coverage. So here's the (new look!) Wireless Waffle guide to practical things you can do to get a better signal (and things that don't work).

best spot for receptionGet high! By far the best way to improve your chances of getting a good signal is to get your phone as high as possible. Signals upstairs will be better than signals downstairs. Signals at the top of a hill will be better than at the bottom. Standing on the roof of your car will get a better signal than sitting inside it (not recommended if you are a bit on the heavy side). Height is the number one way to boost your signal.

Get out! The Ofcom paper mentions this too, but doesn't point out how big a difference it can make. Buildings can shield mobile signals by anything up to a factor of 50. Standing outside will circumvent this shielding and can make a big difference in your chances of success.

Get moving! Buildings not only shield signals inside them but can block signals from passing through them. Other big obstructions such as gasometers, walls, and even trees and cars
can also block signals. As you are unlikely to know which direction the mobile signal you are trying to receive is coming from, you may inadvertently be stood in a position where it is being blocked. Move around (in particular walk around a building) whilst checking the signal on your phone to see if there is a spot where it suddenly comes to life.

abby good receptionGet naked! Whilst we would love to see people walking around buildings in the nude to try and get a better phone signal, by this we mean taking off any covers, shells or other accoutremenets which adorn your phone. Some covers can contain metal elements which can deflect mobile signals, especially if they end up covering up the antenna on your phone. Operating your phone 'naked' will ensure that it's antenna is not blocked or covered in any way and can further improve performance.

Get clear! Most electrical devices, especially computers, TVs, set top boxes and other electronic gizmos give off weak radio interference. The amount they give off is limited by law, but in close proximity it can be enough to upset mobile reception. Make sure you are as far as possible away from any electronic equipment and the interference they generate should be too weak to cause reception problems.

Get plugged in! If your phone has option to connect an external antenna (such as via a car-kit) it might be feasible to connect an free-standing aerial (such as these) to it. The antennas inside phones are a compromise in size, designed to peform as well as possible given the small space in which they have to fit. Plugging in a proper, full-size, external aerial will boost signals, especially if the aerial concerned is high up, outside and clear of any blockages.

Of course, these are the easy answers. There are some more technical solutions that require a bit of effort, like the soup can booster antenna (no, not two cans and piece of string) which really work. As well as things that do help, there are a number of things that don't...


mobile phones onlyPower Strip Antenna Boosters and similar devices that you stick on your phone that claim to be able to improve its performance. Anything that doesn't plug into your phone but just sticks to it is highly unlikely to do anything other than leave a sticky patch when you remove it.

Passive repeaters are a bit of a grey area. Properly installed they may be able to provide some boost in signal indoors, by taking the signal that is received outside and relaying it to the inside. The increase is only likely to be noticeable if you mount the external antenna as high as possible, use very high quality cable to connect the two ends, and stand right next to the internal antenna.

Active repeaters are also a grey area, but for a different reason. They do actually work, and can improve mobile signals if properly installed. But, and it's a big BUT, they are illegal to operate. The only people licensed to use them are the mobile operators themselves. Anyone else using one is breaking the law. Further, if they are badly installed, they can cause interference to the mobile networks actually making reception significantly worse, not just for you, but for everyone else in the area too!

So hopefully you now have a much better idea of what works and what doesn't and can amaze your friends by shouting out the mantra of 'get high, get moving, get naked and get clear' if they are suffering reception problems. They are sure to understand what you mean as you couldn't possibly be misinterpreted, could you?]]> Radio Randomness, Much Ado About Nothing http://www.mf2fm.com/blog/index.php?entry=entry110810-071940 Richard Womersley, G1JAJ Wed, 10 Aug 2011 13:19:40 GMT http://www.mf2fm.com/blog/comments.php?y=11&m=08&entry=entry110810-071940 Radio Killer - Lonely Heart http://www.mf2fm.com/blog/index.php?entry=entry110807-182332 Wireless Waffle. The only real connection with our usual topics is in the title of the band 'Radio Killer' because it contains the word 'Radio'. Anyhow, here's an off-the-wall prediction for a future UK chart topper...



This has got to be one of the catchiest dance tunes this year, beating fellow Romanian Alexandra Stan (of Mr. Saxobeat fame) for the best tune of the year so far.

It's released in the UK on Sunday August 14th, so we shall see whether Radio Killer can indeed kill all others and make it to the top of the chart. Pop pickers!]]> Chart Predictions http://www.mf2fm.com/blog/index.php?entry=entry110807-182332 Richard Womersley, G1JAJ Mon, 08 Aug 2011 00:23:32 GMT http://www.mf2fm.com/blog/comments.php?y=11&m=08&entry=entry110807-182332