Homebrew ADS-B

One of the most interesting and therefore popular things to monitor on a radio scanner are the airband transmissions. Listening to aircraft communicating with air-traffic control can be quite addictive, especially if you are able to hear transmissions from the tower of a busy airport.

Several years ago the geek factor for would be air-traffic controllers soared with the introduction of virtual radar systems. These units monitor the Automatic dependent surveillance-broadcast (ADS-B) that all modern aircraft now transmit in the 1090MHz band.

My younger brother who lives near Birmingham International brought a system a while ago and has great fun watching the approach of aircraft on ‘radar’ as they rattle the roof tiles on approach to BHX.

Not being a wealthy as my brother I have been looking for a cheaper alternative… and on Hackaday perhaps I have found one…or maybe not…

A simple decoder made from some salvaged parts from an old satellite receiver!

http://hackaday.com/2011/09/22/tracking-commercial-aircraft-with-salvaged-electronics/
http://www.lll.lu/~edward/edward/adsb/VerySimpleADSBreceiver.html

Until then I will have to make do with more low tech ACARS decoding.

Hamfest 2010

Took the afternoon of work today and went to the Newark Showground for a few hours to experience the National Hamfest 2010 Despite the weather which was absolutely appauling I had an enjoyable time. I resisted the urge to purchase any new equipment, this was difficult as some very nice receivers, scanners and antennas were on sale.

Because of the rain the intended outdoor carboot section was almost none existant which was a pity as I fancied a rummage. Inside it was mostly new ‘expensive’ gear a few surplus stores and a few clubs and others with some used and ‘junk’ stuff for sale. It is quite noticable that the cheap chinese import transceivers that are flooding ebay were also much on offer and I suspect if I do take the exam and get my licence I will end up with one of those initially.

In the end I picked up some adapters, a few books and I did take advantage of the RSGB special offer and joined up. I also signed up for the Group for Earth Observation (GEO) the members on the stand were very helpful and this was particularly interesting as the members of the group use relatively inexpensive equipment to receive data from satellites to produce weather images and other earth observation. I dabbled many years ago with receiving data from the NOAA polar orbiting APT satellites which can be done to a limited extent using a normal scanner and a PC soundcard. It was only £20 to sign up and the welcome pack for GEO was extremely generous and consisted of the last four quarterly magazines packed full of information and pictures and a lovely book all about the EUMETSAT system.

Station Report

It has been a few weeks since I dug out my neglected scanners and despite not being able to spend hours with them I have still had an enjoyable time reacquainting myself with them and experimenting.

Despite the growing use of digital transmission systems there is still a lot to listen to on the airwaves. I should note at this point that using a scanner to monitor anything that is not intended for ‘General Reception’ is illegal.

The Amateur bands are fairly quite around my location, however I was pleasantly surprised to be able to here to receive a number of Amateur repeaters both on the 2 meter and 70cm bands despite appearing to be outside the predicated coverage.

The CB bands are also very quiet but I suspect that is more to do with the high levels of interference I seem to be suffering. I have been struck by the apparent increase in interference (QRM) on a lot of the bands since I last used the receivers. I can hardly hear anything on the short wave HF bands except the more powerful commercial transmitters.

I suspect this interference is down to the proliferation of computers and associated peripherals, wired and wireless networking. Energy saving fluorescent lamps and microprocessor system in all manner of consumer equipment such as TVs, PVRs, DVD players for example means the airwaves are full of noise.

The Radio Society of Great Britain (RSGB) who represent the thousands of Amateur radio operators have begun to campaign to save the radio spectrum from such interference, specifically they are currently campaigning against the threat poised by the proliferation of PLA/PLT devices (such as HomePlug) these devices use the house mains wiring to transmit network data. However what happens is the wiring then acts an effective radio antenna transmitting the traffic at such levels blocking out other legitimate radio transmissions. This sounds(sic) to be in direct contravention of the EMC Directive of the EU that prohibits the manufacturer of any device that interfers with radio and telecommunications equipment.

However despite representations by the RSGB, the BBC and others OFCOM and the last Government have dragged their heals and refused to act. Hopefully the new Collation Government will be different, but I won’t hold my breath. More information at UKQRM
  
However given all this noise there are still things to listen to, of course I haven’t since it is illegal, but if I were so inclined there are plenty of analogue VHF/UHF Private Mobile Radio (PMR) systems still being used by commerical organisations. Such as taxi firms, councils, security patrols or by large business to facilitate communication across sites.

In the past it would be difficult to know the source of the transmission often listening for clues to try help identify them such as names of locations, buildings, streets and people for example. However nowadays it has been made a little easier by OFCOM who have allowed on-line access to the Wireless Telegraphy Register database. The use and allocation of radio frequencies is strictly regulated so now if get a hit on a frequency it is possible to use the WRT website to help identify them.

The air and marine bands are still as active as ever, given my location near to a number of RAF bases it could prove interesting if I were also so inclined.

Rebooting a lapsed hobby

My current equipment

Ever since I was old enough to handle a screwdriver and a soldering iron I have had an interest in radio communications and electronics. I spent many a hour in my childhood scanning the Medium and Short Wave bands with various receivers (usually scavenged from family, neighbours or saved from the dump!) I constructed numerous long-wire and other bizarre antennas. I even did a presentation on my hobby for my English Language O-Level exam – I really did confirm my status as a weirdo!

I played with borrowed CB radios and would have loved to progressed into owning one or becoming a proper radio amateur but unfortunately I simply didn’t have the money.

Then the home computer revolution started and my Dragon32 and Tatung Einstein took up most of my time. I left school and went off to University and when I came back home and got a job I spent some of my money on a new fangled radio scanner, a Realistic PRO2022 from Tandy.

A scanner is a radio that covers a wide frequency range, they are controlled my microprocessors and allowing you to listen in to a huge range of different communications including air traffic control, hobbyists (Citizens Band, Amateur radio), security guards, taxi’s and a lot more. Back in the late 80s, and early 90s they also allowed access to the emergency services and the old analogue cellular phones! Connecting it up a computer and using some software you even decode pager messages!

Gradually all the ‘fun’ stuff disappeared, the mobile phones became digital, so did the emergency services. This along with other commitments, such as moving across the country to a new job, getting married and other demands on my time meant the scanner ended up collecting dust in the attic.

Several years ago I briefly dusted it off and brought a couple of other second hand scanners including a Realistic PRO2006 and a brand new Alinco-DJ3X. I also played around with some PMR446 systems, but sadly again they all ended up collecting dust.

Well once again they are out of the boxes and I am having a fun time scanning around for interesting signals, well if you can count listening to the radio microphone at a local church interesting!

I am thinking of buying a CB as it seems to have evolved from the bad old days into something more grown up. Even becoming a DX amateur type system using something called freebanding not legal mind, but then technically using a scanner isn’t!

I am even contemplating taking the Radio Amateur exams and actually achieving a childhood dream, well I do now have access to money and did do an electronics degree!

This time I hope it doesn’t all fizzle out and it is looking more promising as plans are a foot for me to have my own shack and I won’t be spending as much time on my other hobbies next year.