AIRBAND LISTENING
My ShortWave Listening hobby began as a young child and it stayed with me for decades (apart from the usual periodic lapses when life serves you lemons). When I started to go to Airshows and Airports in my 20's, it was only natural that I became interested in the on-air chatter between pilots and ground stations. Of course back then, the AM airband receivers (that I could afford) were extremely basic and not particularly sensitive, but they were good enough to maintain an interest. As I got into my 30's, things had got significantly better and I could afford equipment from Yupitera, Alinco and AOR. Their scanning receivers had huge frequency ranges, multiple modes, memories and blisteringly fast scanning speeds!!Rather than just scan the airband for local traffic, I soon became curious about how it all worked and searched outside the AM sector for signals of a more DX nature. I was never going to become obsessed with it, because I had other hobbies too, but I did at least want to go further than the average spotter at the runway apron.
So, here's my understanding of it. I'm no expert - far from it - but learning just a little more about how it all works, can greatly enhance your enjoyment.
The world's airspace is split up into regions called Flight Information Regions (FIR). Some countries may only have one FIR due to their small size, while others need multiple FIRs because their country is physically huge.
As aircraft pass through our airspace, you may hear them on the approach seeking permission to enter, for example, the LONDON FIR and then soon after being told to contact the SHANWICK FIR to continue their journey over the Atlantic to their final destination.
Apart from horizontal splits across land, vertical splits also exist. You can (and usually do) have an upper and lower FIR (the lower one being referred to simply as FIR and the upper one being called UIR). Upper Airspace is normally regarded as being the space above 24,500ft (FL245).
Here in the UK we have 3 FIRs with the callsigns LONDON, SCOTTISH and SHANWICK OCEANIC. The London FIR covers England and Wales. The Scottish FIR covers Scotland and Northern Ireland. The Shanwick FIR covers the North East Atlantic.
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| FIRs |
Because of the size and the amount of traffic, LONDON FIR uses additional resources at Manchester Airport to aid control of the vast number of flights passing through England and Wales.
Around 6,000 aircraft fly through our airspace every day and all that traffic is controlled by the Civil Aviation Authority and split into sectors classified as A, C, D, E or G and our airspace (broadly speaking) is either controlled or uncontrolled.
Uncontrolled airspace (Classified as G) has no restrictions on which aircraft can enter it or the routes aircraft can take. Class G is basically any airspace which doesn't have one of the other classifications. And it's not just a horizontal space from A to B, it's also a vertical space from ground to a certain height (usually expressed in feet). Class G's ceiling-height will be Class E's floor-height. Pilots flying in Class G airspace are responsible for their own navigation, separation from other aircraft, obstructions, etc, but a pilot can ask for help.
All other airspace is Controlled - rigidly controlled! Different classifications exist in order to provide safe movement across the skies of the UK. Here's what the different classes mean in real terms...
CLASS-A requires a pilot(s) to be certified to fly on Instruments Only (IFR) and not rely on what he sees outside the window. This is the most strictly regulated airspace of all and pilots must observe and follow every instruction given by the local air-traffic-controller (ATC). Aircraft which operate in Class-A airspace are kept well away from other traffic and are usually comprised of large commercial airliners.
CLASS-C is an airspace (in the UK at least) which is at a flight-level between 19,500ft (known as FL195) and 66,000ft (FL660). In Class-C airspace, pilots can operate IFR (Instrument Flight Rules) or VFR (Visual Flight Rules), but they must request permission to enter the airspace and must comply with ATC instructions.
CLASS-D is like Class-C in that pilots can work to IFR or VFR but Class-D is typically assigned to the areas around airports and aerodromes and have a speed limit of 250kts when the aircraft is below 10,000ft. Again, pilots must obtain permission to enter Class-D airspace and must comply with ATC.
CLASS-E permits either IFR or VFR. IFR traffic need to request permission to enter this airspace and comply with all ATC instructions, where VFR traffic does not.
Air Traffic Controllers can only control a limited amount of aircraft at any one time, so the country is split into sectors and the number of sectors can vary according to the time of day and even the time of year - the more traffic, the more sectors. When it's less busy (such as night time), some sectors will be grouped together with fewer controllers managing a larger area. A bit like a superstore opening more tills on a Saturday morning, but closing many of them down on a Sunday afternoon 😅
Responsibility for Transatlantic traffic is shared between the UK, Portugal, USA, Canada and Iceland. Aircraft stick to predetermined routes which are published every 12 hours and these routes are generated according to weather conditions and in particular, tailwinds which can help traffic make enormous savings in fuel. Approximately 80% of all Transatlantic traffic goes through Shanwick Oceanic - it's the gateway to Europe!
It's worth noting that while radar is useful for determining the position, heading and speed of aircraft, it only has a range of around 250 miles due to the curvature of the earth, so aircraft "squawk" their unique ID and positional data electronically (by satellite or radio) every so often in a data-burst and this information is gathered by ATC's across the world to form a picture of what's going on.
It's possible for you to play an active part in monitoring air traffic in your area by using a simple bit of hardware and software with a tiny antenna mounted (ideally) outdoors above your roofline. It's called Automatic Dependent Surveillance-Broadcast (ADS-B). We'll talk about this later.
IS IT LEGAL TO LISTEN IN?
You need to be aware that it is ILLEGAL to monitor the Airband in the UK! You're okay to purchase an Airband receiver or even purchase a Transceiver like I did, but you are not allowed to listen to it. Crazy, I know, but that's how it is.
Needless to say, you are extremely unlikely to be prosecuted for listening in, but just be aware that the authorities do have the right to confiscate your radio, but you only have to walk around the airport perimeters and viewing parks to see scores of people watching aircraft traffic while listening to pilot/control chatter on their radios with no objections from airport staff or authorities.
SO WHAT CAN YOU LISTEN TO?
Most people simply tune into their own local airport Approach & Tower frequencies and listen to the two-way comms relating to take-offs and landings. That in itself can be quite interesting, especially as a background fill-in while you're doing something else. You'll occasionally get a bit of excitement in the way of a Go-Around or reports of someone kicking off on a plane 😂
If you are reasonably close to an airport, you should also be able to pick up GroundCrew transmissions. These can be quite mundane but occasionally turn up some interesting situations. If you are too far from an airport, you will only hear the aircraft above you (up to around 200 miles away on VHF).
You can also listen to ATIS transmissions where messages are repeated continuously, relaying information on local weather conditions and other important information. There are also VOLMETS which perform a similar function but with information relating to a much wider area. Bit boring but sometimes useful as a measure of conditions.
Hand gliders, Balloonists and Gliders use a specific frequency, so if you're visiting a local event, you can always listen in to what's going on.
If you program your radio to monitor the Distress Frequency (121.5MHz Civil, 243.0MHz Military), you will very occasionally hear a bit of drama which, thankfully, is usually nothing too bad.
Airport Fire Services have a fixed frequency, so if you see any movement of fire engines while at an airport, you can always tune in and see what's happening (might just be a drill).
Finally, you will very occasionally hear a bit of an argument between ATC and Pilots. They're very rare, so keep your recorder going!
WHICH MODES / FREQENCIES?
The vast majority of civil-aviation chatter occurs on VHF frequencies using AM. Occasionally you may find some Military action on VHF too - usually at an airshow.
Military flights usually use UHF frequencies between 225MHz and 400MHz. Obviously, you will find it much easier to monitor Military Flight activity if you live close to a Military AirBase or on a route to one.
For long-distance transmissions, pilots may use HF and there's a number of common frequencies between 2MHz and 23MHz where you'll find activity. Needless to say, it's nowhere near as busy as your local VHF chatter.
With regard to specific frequencies, you can easily Google the airport frequencies local to you or visit a website such as the UK AIRPORT & AIRFIELD site or the MILITARY AIRSHOWS UK site and obtain them from there.
Alternatively (or in addition) you can buy an Airport Frequency Reference Book. These books don't age as quickly as you might expect and they always contain additional information. Just bear in mind that books contain very comprehensive lists of frequencies, but most of them will relate to activity way outside your area and therefore of little interest (unless you travel around a lot).
Note that spacing is usually 25kHz but 8.33kHz will be used increasingly See THIS document about 8.33.
WHICH EQUIPMENT TO USE?
If you're not convinced that Airband Listening is for you, then you'd be ill-advised to spend too much on radio equipment at this stage. You're probably better off buying the cheapest scanner available so that you can sell it if things don't work out for you. You'll probably not lose any money - especially if you buy something used on eBay. Just bear in mind that the really cheap stuff only works well if you're at an airport spectator park or live closeby, so don't expect too much.
If you are already convinced that the AirBand is for you, then it all depends on your budget and whether or not you want your new radio to receive other stuff in addition to AirBand signals. There's a lot of cheap scanners out there which will cover a very wide frequency range, but they should be considered as Jack Of All Trades and Master of None.
Personally, I would recommend the YAESU FTA-550 Airband Transceiver over a scanner like the UNIDEN UBC-125XLT. The Yaseu is dedicated to the AirBand and is superbly well built. Needless to say, you need to disable the TRANSMIT function by changing a menu option.
If you think most of your listening will be done solely from home, you might want to consider an excellent (and cheap) RSP1A from SDRPLAY. These cover an extremely wide range of frequencies and provide you with a plethora of amazing functions and features BUT you need to connect it to a PC to work.
One of my favourite handhelds for AirBand and other bands is my 20yr old ALINCO DJ-X2000. It cost a fortune back in the day and was probably the most advanced scanner in the world upon launch. It still works very well to this day, although the HF tuning is out a couple of kc. I just love this radio and will never sell it.My 30yr old AOR AR-3000A is another great bit of kit to monitor with. It covers everything from the lowest to the highest and is super sensitive. There's plenty around on eBay still (although some people are a bit deluded when it comes to pricing them).
Being a licensed ham, I do, of course, have other radios which are capable of monitoring the AirBand and I use them regularly. My Kenwood TH-D74 is one such radio and it performs magnificently but it's a very expensive bit of kit and I wouldn't take it to an Airport Spectator Park because I'd be terrified of losing it or dropping it, lol. Not only can it monitor AirBand, but it also covers HF and has SSB.
My YAESU FT-3D covers the AirBand and is quite sensitive at those frequencies but it has no SSB capability.
Most VHF/UHF ham radios include access to the AirBand and some do it better than others, so if you already have such a rig, there's no point in spending more. And don't forget that your Shack-In-A-Box will almost certainly have Airband receive capability as well as HF SSB. Things like the IC-7100, FT-991A, FT-818, etc.
Another favourite radio of mine is the TECSUN PL-680 which has a very useful form factor. It covers the AirBand and also HF with SSB. It has lots of memories in which you can store frequencies. Super portable and very flexible around the home for general domestic use too. Its bigger brother the S-2000 performs pretty well but is quite cumbersome. Both Tecsuns have external antenna options.
Sometime in the hopefully not too distant future, AOR will get round to releasing their flagship AirBand receiver - the AR-7400. It will no doubt be quite expensive, but will hopefully set the gold standard for AirBand Scanning Receivers.
There are a LOT of other options out there and I would suggest you spend some time looking at the radios available online. Martin Lynch are a very good source for both new and used equipment and might be a good starting point, but there are other stores you available in the UK, including Moonraker. You can pay anything from a few pounds to a few thousand pounds.I'd recommend that you see if you can borrow a radio from a friend or club before spending big bucks on something.
ADS-B : MONITORING LIVE TRAFFIC
If you have a mind to, you can setup a low-cost station which will gather all the information which aircraft broadcast using a system called Automatic Dependent Surveillance Broadcast (ADS-B). This information includes all the data relating to the aircraft's ID, its position, heading and speed.
As you can see from the diagram below, the aircraft obtains its positional data from the GNSS satellites and then transmits it to Ground Stations and other aircraft around it.
Anybody can gather this data and by doing so, you can actually be part of the system by uploading your gathered data 'on the fly' to interested parties. In order to build your own Ground Station, you'll need the following...- A computer (Raspberry Pi with SDCARD)
- A connection to the internet
- A FlightAware USB stick
- A Tiny 1090MHz antenna
- A FlightAware Account
You can see from the photo above that I chose a Raspberry Pi Zero 2W which are very cheap, very small and perfectly capable of running the software. I bought one with the optional aluminium case which doubles up as a heatsink.
There are a number of ADS-B RECEIVER dongles on the market, but the very best is the FlightAware Pro Plus because it has a built-in preamp and built-in filter. It's therefore far more reliable at decoding than others and will give you superior results, for just a small premium.
As a contributor to the ADS-B data system (ie, you're uploading all the aircraft data gathered from your Ground Station), you can obtain a FREE Enterprise account which would normally cost you around £90 per month, giving you full access to the system.
SAMPLES
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| Traffic over Europe with Weather |
Click on the image below to read the full installation guide. It's all very straightforward and you'll be up and running in no time at all...
If you have anything to add to this post, please make a comment in the COMMENTS SECTION below and don't forget to add your name (and callsign if you have one).
Thanks for visiting the blog.
Tom, M7MCQ.
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