Wednesday 16 November, 2005, 07:59 - Radio RandomnessAccording to an article in yesterday's London 'Metro' newspaper, experts from the highly respected Massachusetts Institute of Technology (MIT) have spent about US$200,000 showing that aluminium hats, similar to those worn by Mel Gibson in the film 'Signs' serve to reduce radio signals at most frequencies, but that some frequencies were amplified by the shiny metal toupees. The report 'On the Effectiveness of Aluminium Foil Helmets: An Empirical Study' went on to show that the frequencies which were amplified were ones which had been allocated to the US Government and thus concluded that this was some kind of conspiracy to conduct mind control of US citizens.
However the truth about the MIT study is rather different. The students used equipment worth US$250,000 (rather than spending that much) in the form of a network analyser to determine the gain of the 'hat' at different frequencies. They concluded that the hats had peaks in gain at 1.2 and 2.6 GHz (not surprising if one does a few simple sums concerning the typical size of a human head and the frequency at which such hats would naturally resonate) and went on to conclude that as the first of these frequencies was used by GPS satellites broadcasting Government signals from the sky, that the hats may well increase the Government's invasive abilities.
If this were to be the case, then the US Government would have to emit high power 'mind-altering' signals on those frequencies. However, much more importantly, they would have to make all the citizens wear silly aluminium hats, which as far as I am aware is not yet mandatory (except, presumably, at some of the more wacky parties at MIT!)
Further, GPS satellite signals are very weak compared to the extremely high-powered aeronautical radar systems that share the frequencies around 1.2 GHz, so if any signal were likely to affect the wearer it would be those coming from the radars at airports (and the corresponding transponders on aircraft). Aeronautical radars (both civil and military) also occupy frequencies beginning at 2.7 GHz (very close to the other measured gain hot-spot). Could this explain the increase in the number of air travellers around the world? Or might it explain why, after a long flight, you feel dazed as you depart the airport? Or is this a conspiracy to increase the sales of duty free?
Why not try wearing one of the hats the next time you visit an airport and see if you can note any unusual effects? Remember not to take it off when you pass through the airport scanners, otherwise the experimental value of the research will be lost. Wearing camouflage, a head scarf and carrying a replica AK-47 are also known to enhance the effectiveness of such airport-based experiments and often make the results more immediate and obvious.
Thursday 20 October, 2005, 09:07 - Radio RandomnessYou often read about 'strange signals' being heard on various frequencies; there are lots of web-sites which provide listings of the frequencies on which these oddities can be heard. But I was surprised to discover that there are some weird goings on in the amateur bands. Not, that is, because they are in any way sacrosanct, but because these things often occur in the 'twighlight zone', i.e. those frequencies which don't seem to belong to anyone in particular because they sit between Fixed, Mobile, Amateur, Broadcasting and other allocations.
My attention was drawn to 'Cluster Beacons': a series of CW (Morse) transmitters which are clustered very closely together in frequency and do nothing other than transmit the same letter over and over (and over) again. Such beacons have apparently been heard in the 40m amateur band occupying frequencies on or just below 7039 kHz. Now usually such things can only be heard by people with mile-long multi-element beam antennas and ultra sensitive receivers so I tuned my receiver to the frequency in question expecting to hear absolutely nothing (always the optimist). To my surprise, not only were these cluster beacons audible but (especially during the hours of darkness) they put quite a good signal into the UK. In particular the 'C', 'D', 'O' and 'S' beacons are audible for most of the day.
Not much is officially written about what the purpose of such beacons might be, however the received consensus is that they are either for monitoring propagation or are for navigation (the spectrogram on the right shows a waterfall of one of the clusters in action). What is known is that they come from various cities in the Former Soviet Union; each city is represented by a unique letter. This is a list I found elsewhere, I have no idea how accurate or up to date it is:
'K' Peteropavlovsk Kamchatskiy
'L' St. Petersburg
As well as being clustered around 7039 kHz in the 40m amateur band, other cluster hot-spots are noted as being 5154, 7039, 8495, 10872, 13258, 16332 and 20048 kHz. I checked these and found that as well as those around 7039, beacons around 10872, 16332 and 20048 kHz were audible during the day (as of October 2005).
Whatever purpose these beacons officially serve, they are useful as a propagation check, if you happen to want to use HF to be communicating with Russia. Alternatively, if you can find a nice clear frequency where only the beacons are audible, the gentle tonal pulsating of the beacons is strangely hypnotic!