Wireless Waffle - A whole spectrum of radio related rubbish
Strange Signals from Outer Space!signal strength
Wednesday 24 May, 2017, 09:53 - Radio Randomness
Posted by Administrator
bbc horizon logo

Just a quick plug in case you missed it... BBC's Horizon programme has just aired an episode entitled 'Strange Signals from Outer Space!' which examines the (so far unsuccessful) search for extra-terrestrial intelligence (SETI). It finishes with a look at star KIC 8462852 (also known as Tabby's Star) where astronomers believe that there may be the beginnings (or remnants) of a Dyson Sphere.

If you aren't familiar with the concept of a Dyson Sphere (which is nothing to do with vacuum cleaners), it's worth reading hard-fiction novel Pandora's Star by Peter F. Hamilton whose story begins with an astronomer discovering a star that suddenly and mysteriously vanishes. It is the supposition of the scientific community that it has been encased in one of the aforementioned Dyson Spheres by a civilisation far more powerful than humans.

An exploratory mission to visit the star causes it's equally unexplained reappearance but this, in turn, leads to potentially devastating implications for the human race. It's the first book in a series (as all sci-fi novels seem to be these days) but it comes with the Wireless Waffle 'big thumbs up' seal of approval.

seti finally succeed
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Hear no Alien, See no Alien, Speak no Aliensignal strength
Tuesday 18 April, 2017, 15:37 - Radio Randomness
Posted by Administrator
alien radio transmissionsHere at Wireless Waffle, we have taken quite an interest recently in deep space communication with Mars and Jupiter and the search for extra-terrestrial intelligence (SETI), considering whether we are, for example, listening on the wrong frequency.

It seems, however, that even the professionals are having difficulty in detecting any signals from remote solar systems. The Guardian newspaper reports that 'the most ambitious alien search to date draws a blank'. The Breakthrough Listen project had found a number of promising signals, however despite innovative software and algorithms and $100 million of funding, all of these turned out to be terrestrial in origin.

At the same time, whilst we are listening, should we not also be attempting to transmit signals for others out in the great black beyond to receive. After all, no-one would know that we are here unless we shout about it.

Many fear the consequences of us raising awareness of our existence. They claim that if we were to announce to the universe that we are here, 'minds immeasurably superior to ours would regard our Earth with envious eyes' (to paraphrase HG Wells). The 2015 Hugo award winning novel The Three-Body Problem by Cixin Liu explores this precise issue (as well as providing a tantalising glance of a futuristic on-line game designed to route out only the most intelligent). Originally written in Chinese, the book picks up the story of a remote Chinese 'radar' station whose function is not quite as navigational as it seems. It's in the process of being made into a feature length movie too (albeit in Chinese).

It stands to reason, however, that if we shy away from transmitting the occasional signal to alert anyone that is listening that we are here, it would be logical to assume that any other intelligent civilisations may have taken the same cautious approach. Hence we will never hear from them and they will not hear from us. This doesn't mean we should give up, but it does question the logic of listening intently, whilst not speaking.

hear speak see no alien
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A Jovial Receptionsignal strength
Wednesday 29 March, 2017, 09:15 - Radio Randomness, Spectrum Management
Posted by Administrator
Wireless Waffle has previously discussed the idea that it might be possible to receive radio transmissions from alien planets, but it might not be widely recognised that it is possible to receive radio transmissions from planets within our very own solar system!

mobile phone on jupiterIt turns out that the planet Jupiter emits a range of different radio transmissions, not from people using mobile phones on the planet's surface, but so called long 'L' bursts and short 'S' bursts which are generated by the planet itself and its interaction with its moons, and that these signals are relatively easy to receive here on good old planet Earth. These emissions range in frequency from a few kHz to around 40 MHz. The Jovian signals get weaker the higher in frequency you go, but the lower frequencies are often absorbed by the Earth's ionosphere. In addition, many of these frequencies can be replete with short-wave transmissions. What is needed, therefore, is a frequency that is high enough to pass relatively unperturbed through the ionosphere, but low enough to be receiveable, without too much interference.

An obvious place to start would be the Radio Astronomy frequency allocation between 25.55 and 25.67 MHz as these frequencies should theoretically be free of all other radio transmissions. But it seems the frequency of preference for catching the latest bursts from Jupiter is actually 20.1 MHz, which is the frequency selected by NASA's Radio Jove project. From a radio spectrum perspective this is a relatively odd choice of frequency (e.g compared to the theoretically clean Radio Astronomy allocation). At an international level, frequencies around 20.1 MHz are allocated primarily to the fixed service, with a secondary allocation to mobile services. A quick scan of the Globaltuners database shows AT&T usage on 20.095 MHz and US Civil Air Patrol on 20.107 MHz. However, it seems that the signals from Jupiter at higher frequencies are much weaker, even by the time 25 MHz is reached.

radio jove antennaSo what do you need to listen to these mysterious signals? A simple short-wave radio should do the job, however it is said that there are two additional things which need to be done in order to tune in to Jupiter:
  • Turn off the AGC (automatic gain control) on the receiver. The AGC apparently tends to mask the bursts. A software radio is ideal for this.
  • Build a simple directional antenna.

The latter of these is the most difficult. A two-element array is what the experts say is needed, and at 20 MHz, this is roughly 8 metres (26 feet) square as the diagram on the right shows.

Notwithstanding a lack of the correct antenna, Wireless Waffle sought to attempt to receive Jovian radio signals using a short-wave receiver and a normal short-wave antenna (not the fancy two-element arrangement). Sadly, our attempts did not yield any L or S bursts that could be definitively identified as transmissions from Jupiter. We did however manage to receive:http   allbum it  ash girl from mars remixSo though we failed to receive any Jovian signals, we did receive some jovial ones and therefore maybe it wasn't such a pointless exercise as at first it might have seemed! Why not give it a go yourself and let us know how you get on?
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We're Jammin' (Part V)signal strength
Monday 19 December, 2016, 13:59 - Amateur Radio, Broadcasting, Spectrum Management
Posted by Administrator
keyfob womanWireless Waffle last discussed the issue of interference to and from wireless car keys and other similar devices back in 2013, but the topic has cropped up here almost since time immemorial. The original articles discussed the fact that the frequency band used for these devices (around 433.925 MHz) was shared with radio amateurs and that not only were the radio amateurs suffering from interference but that there were cases of car users getting stuck either unable to lock or unlock their cars due to nearby amateur radio transmissions.

But it seems that the situation has changed and that criminals have cottoned on to the fact that it's possible to jam the transmissions between cars and their keys to their benefit. The BBC reports that thieves in a car park in Berkshire had been 'using car key jammers' and also provides useful advice on the impact and implications of car key jammers.

Now far be it for Wireless Waffle to condone such activities, but it is so brain-achingly simple, and mind-bogglingly cheap, to jam these signals, that it's a surprise that it has taken criminals so long to figure out how to do it.

pofung 40w uhfTransmissions from car key fobs normally use either amplitude modulation or fairly crude frequency modulation and the transmitters have a power level of no more than 10 milliWatts. The receivers in the vehicles are manufactured to a price point of around 50 pence and are woefully inadequate at protecting against interference. Thus, a strong enough signal on the same frequency as the car key transmitter (or indeed on a neighbouring one) will overwhealm the low power transmission from the keys. A 40 Watt transmitter (4000 times stronger than the signal from the keys) operating in the same band can be purchased on-line for little more than GBP100.

Such a transmitter would be a brute force way to stop the receiver in the car from being able to hear the signal from the key. This would stop the key from being able to lock the car, meaning that an unsuspecting driver could get out of the car and casually press the button on their key and walk away without listening for the corresponding 'clunk' of the car locking, not realising that the car has not locked. This would clearly leave the car unlocked and easy pickings for a thief.

In principal it would be easy to go one stage further. With a simple receiver it would be possible to record the transmission from the key, and using a low power transmitter, it would be feasible to re-create the signal. In this case, it would be possible for a criminal to unlock a car after it had been safely locked by the driver. Don't say we didn't warn you.

car thiefThis is not just possible for car keys, but for any devices which operate in a similar manner. The 433 MHz band used for these devices is replete with a variety of signals from wireless devices such as garage doors, parking barriers and devices for which an attack would be less significant such as weather stations and doorbells. The chart below (known as a waterfall chart) shows, from top to bottom, around 2 minutes of time, and from left to right, the middle portion of the 433 MHz band. A wide range of different transmissions are shown as bars or dots and it is clear there's plenty afoot here despite the transmission area of the devices being very small and thus the limited number of devices in range of the receiver used to perform this scan.

433 mhz band scan

As the number and variety of wireless devices increases, in particular as we progress to the world of the 'Internet of Things' in which there will be sensors and actuators everywhere, it is clear that the security of wireless connections needs beefing up. If you are concerned about your car being 'hacked' by criminals, the best way is to disable the convenience of the wireless key locks and return to the old-fashioned technique of putting the key for your car into the door. Sadly, some modern cars don't actually have this feature any more!
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