A couple weeks ago, the TVRVBG was discussing the problem of IFR practice, and VFR traffic not knowing where they were, since they were talking to controllers on other frequencies. I posted this suggestion to their group on May 27. Nothing at all was heard. One guy suggested that I post it here. So I pasted it below:
I installed an APRS system in my project. Every 30 to 35 seconds while in flight, I transmit my ID, position, heading, speed and altitude on a 2-meter Amateur radio frequency (144.39 MHz, FM, 5 KHz deviation) to the world. That transmission could be picked up by any airplane within 15 to 20 miles of me at any time, and up to 75 miles sometimes. It takes about 1 second to transmit. Since it is FM, if two airplanes were transmitting at the same time, the closest is the one that will be heard.
This system is called APRS (Automatic Position Reporting System), and my data packets are heard on fixed ground stations, making it to an Internet Gateway, and then several servers access this data, like the two shown below (showing my project in my shop in my back yard).
http://db.aprsworld.net/datamart/switch.php?call=wa8vwy-7&maps=yes
http://www.findu.com/cgi-bin/find.cgi?call=wa8vwy-7&terra=4
It would be little trouble to intercept my packets and display the position of my airplane relative to another airplane in flight ? just some development work and cheap equipment is needed. This could solve a lot of problems for everyone, not to mention it could provide an ?artificial radar? to every grass field in the world who had a PC. It would also take a dedicated frequency where a low power (0.1 watts is plenty) and a 10 KHz deviated FM signal could be used. If this were to become a standard, people like Garmin would probably add it to their GPSMAP line, with the data input coming from their RS-232 input to the unit. The 10 KHz deviation would allow the packet transmission speed to double, allowing 0.5 second transmissions.
The transmitter, dedicated GPS and power supply for the APRS in my project is less than $125, and it could have been less if I had used a different radio ? I used an ICOM 2AT. I installed everything in the space under the channel that the seat backs rest on, behind the pilot?s seat back (RV-7 or 9). I installed a piece of thin steel plate at the center of that channel, between the seats, so that the dedicated GPS with its mag mount would sit there, and the rubber duck antenna also shares some real estate with the GPS.
Bottom line: This is a re-application of something that was developed over 10 years ago, and is fully mature. The only problems I see are political ? like finding a piece of radio spectrum to use ? I propose the top 10 KHz of the current aircraft spectrum, since we already have airplane antennas that are tuned closely to these frequencies (cut 2 inches off, and they are much closer to the top end). The other political problem would be with the FAA. These two political problems are really all that holds us back from such a system.
Added comments, 6/10/2007:
There are a few systems that provide pseudo traffic reporting by listening to transponder replies, but those systems are weak in providing a nice visual display of the traffic. If there was enough interest, Garmin could add the APRS traffic information to their GPSMAP products. This would provide a nice visual display of traffic that was reporting their positions, because the APRS packets contain GPS coordinates that the Garmin can instantly pinpoint on its display, showing relative positions to your current position. The Garmin GPSMAP series has an RS-232 interface built in. A dedicated receiver for this one frequency, with a modem to convert the FSK signals to serial RS-232 data would be fairly inexpensive.
I installed an APRS system in my project. Every 30 to 35 seconds while in flight, I transmit my ID, position, heading, speed and altitude on a 2-meter Amateur radio frequency (144.39 MHz, FM, 5 KHz deviation) to the world. That transmission could be picked up by any airplane within 15 to 20 miles of me at any time, and up to 75 miles sometimes. It takes about 1 second to transmit. Since it is FM, if two airplanes were transmitting at the same time, the closest is the one that will be heard.
This system is called APRS (Automatic Position Reporting System), and my data packets are heard on fixed ground stations, making it to an Internet Gateway, and then several servers access this data, like the two shown below (showing my project in my shop in my back yard).
http://db.aprsworld.net/datamart/switch.php?call=wa8vwy-7&maps=yes
http://www.findu.com/cgi-bin/find.cgi?call=wa8vwy-7&terra=4
It would be little trouble to intercept my packets and display the position of my airplane relative to another airplane in flight ? just some development work and cheap equipment is needed. This could solve a lot of problems for everyone, not to mention it could provide an ?artificial radar? to every grass field in the world who had a PC. It would also take a dedicated frequency where a low power (0.1 watts is plenty) and a 10 KHz deviated FM signal could be used. If this were to become a standard, people like Garmin would probably add it to their GPSMAP line, with the data input coming from their RS-232 input to the unit. The 10 KHz deviation would allow the packet transmission speed to double, allowing 0.5 second transmissions.
The transmitter, dedicated GPS and power supply for the APRS in my project is less than $125, and it could have been less if I had used a different radio ? I used an ICOM 2AT. I installed everything in the space under the channel that the seat backs rest on, behind the pilot?s seat back (RV-7 or 9). I installed a piece of thin steel plate at the center of that channel, between the seats, so that the dedicated GPS with its mag mount would sit there, and the rubber duck antenna also shares some real estate with the GPS.
Bottom line: This is a re-application of something that was developed over 10 years ago, and is fully mature. The only problems I see are political ? like finding a piece of radio spectrum to use ? I propose the top 10 KHz of the current aircraft spectrum, since we already have airplane antennas that are tuned closely to these frequencies (cut 2 inches off, and they are much closer to the top end). The other political problem would be with the FAA. These two political problems are really all that holds us back from such a system.
Added comments, 6/10/2007:
There are a few systems that provide pseudo traffic reporting by listening to transponder replies, but those systems are weak in providing a nice visual display of the traffic. If there was enough interest, Garmin could add the APRS traffic information to their GPSMAP products. This would provide a nice visual display of traffic that was reporting their positions, because the APRS packets contain GPS coordinates that the Garmin can instantly pinpoint on its display, showing relative positions to your current position. The Garmin GPSMAP series has an RS-232 interface built in. A dedicated receiver for this one frequency, with a modem to convert the FSK signals to serial RS-232 data would be fairly inexpensive.
