Re: [Flightgear-devel] [OT]: Range of radios
Holger Wirtz wrote: On Tue, Feb 13, 2007 at 05:49:48PM +, Steve Hosgood wrote: [...] So, Holger, if you arrange that all radio transmission packets in FG/MP carry the transmitter's wattage and the location of the source, you can work out the straight-line distance from yourself (call it 'd'), and then do something like: pkt = get_packet(); d = sqrt(sqr(my_x - pkt-x) + sqr(my_y - pkt-y) + sqr(my_alt - pkt-alt)); if (sqrt(pkt-transmitter_power)/d my_receiver_sensitivity) /* I can't hear this guy */ chuck_packet(pkt); else decode_packet(pkt); This sort of thing would maybe allow ATC (who might have more sensitive radios) to hear people that the local Cessna pilots can't hear. And that might be quite realistic. The problem with a more sensitive radio is that real radio communication is unidirectional and my implementaion using VoIP is bidirectional based on conference rooms (a star topology). The range decision is made on the position of the plane towards the position of the tower. If this range is outside a specified range calculation (see your formula :-) and perhaps a threshold detection) the plane-client hangs up the line. For the ATC this means that he can hear _every_ voice traffic on his frequency (he has an infinite sensitive radio). Because frequencies are often more than one time occupied (world wide) the virtual frequency is a combination of ICAO and frequency. To improve things, you might like to make sure that the straight-line distance 'd' between yourself and the transmitter does not get close to ground. You'd have to factor in curvature of the earth and any mountains if you wanted to get it right. If the straight line gets within a couple of wavelengths of ground, you start getting attenuation and multipath distortion and all sorts of stuff(*). For a first cut, ignore all that and just use 'd'! Notice also how you could arrange to degrade packets if they get received very close to your receiver's sensitivity (you could add noise, distortion etc) which again would add to realism. My code suggestion above just models an unrealistic sharp cutoff when the signal gets too weak, but IIRC aviation radio is AM deliberately because that's *not* how AM radio behaves as it nears the sensitivity limit. Ok, I see... your formula and a threshold detection for eliminating flapping should be a good practice. Thanks! Holger Steve. (*) The BBC (amongst others) have done a load of work in this area to do with predicting service-areas of radio and TV transmitters. Some of it is on the net. Hi, I've had a chance to review the path loss formulae Very simply, the height factors of the TX and Rx aerials is only used to translate what might be an oblique angle into a horizontal distance, in all reality when ATC becomes important the path distance between point to point and terrestial distance can be ignored. The frequency factor can be formed into a constant mid-band freq of say 118Mhz As has been stated, the rain attenuation etc can be ignored as being insignificant at VHF Assume standard TX power of 25W ( I stand corrected 25W= 14dBW or 34dBm ...not 17/37) Assume standard RX sensitivity of -114dBm for 12dB SINAD (roughly translated signal to noise) Assume all cable losses are balanced by aerial gains (eg no extra losses or gains) with all these assumptions a distance of 461km pops out of the formulae. what is perhaps more significant and can't be assumed or ignored is co-channel interference (previously referred to as clutter I think) as a starting point I would use 461 km and concentrate on simulating clutter or doubling and maybe making distant signals more noisy ( double the noise for each extra 100 km) Cheers Dene - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
Dene, On Wed, Feb 14, 2007 at 09:02:54PM +1300, Dene wrote: [...] I've had a chance to review the path loss formulae Very simply, the height factors of the TX and Rx aerials is only used to translate what might be an oblique angle into a horizontal distance, in all reality when ATC becomes important the path distance between point to point and terrestial distance can be ignored. The frequency factor can be formed into a constant mid-band freq of say 118Mhz As has been stated, the rain attenuation etc can be ignored as being insignificant at VHF Assume standard TX power of 25W ( I stand corrected 25W= 14dBW or 34dBm ...not 17/37) Assume standard RX sensitivity of -114dBm for 12dB SINAD (roughly translated signal to noise) Assume all cable losses are balanced by aerial gains (eg no extra losses or gains) with all these assumptions a distance of 461km pops out of the formulae. what is perhaps more significant and can't be assumed or ignored is co-channel interference (previously referred to as clutter I think) as a starting point I would use 461 km and concentrate on simulating clutter or doubling and maybe making distant signals more noisy ( double the noise for each extra 100 km) [...] Ok, thanks! That's quite a wider range as i thaught. Regards, Holger -- # ## ## Holger Wirtz Phone : (+49 30) 884299-40 ## ## ## ### ## DFN-Verein Fax : (+49 30) 884299-70 ## ## ## Stresemannstr. 78E-Mail: [EMAIL PROTECTED] ## ## ## ## ### 10963 Berlin # ## ## ## GERMANY WWW : http://www.dfn.de GPG-Fingerprint: ABFA 1F51 DD8D 503C 85DC 0C51 E961 79E2 6685 9BCF - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
On Tue, 13 Feb 2007, Holger Wirtz wrote: I think I will present a beta-release of the VoIP-Com-Package for FG the next weeks. For realism purposes I have a simple question: What is the normal range for the Voice-COM-Equipment in a plane? I think that a COM1 in a Cessna is not as one of an Airbus. I know that exact range answers are depending from more parameters than only the output power... What I need is a simple number which should describe the maximum range og a COM1. For example 5 km? oder 20 km??? Hi, I'm no expert in this area but isn't most aviation radio communication in the VHF frequency range? I think VHF transmissions are mostly limited to line of sight unless something unusual is going on.. See t.ex. http://en.wikipedia.org/wiki/VHF Cheers, Anders -- --- Anders Gidenstam mail: andersg(at)gidenstam.org WWW: http://www.gidenstam.org/FlightGear/JSBSim-LTA/ - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
Am Dienstag, 13. Februar 2007 15:31 schrieb Holger Wirtz: power... What I need is a simple number which should describe the maximum range og a COM1. For example 5 km? oder 20 km??? No such constant number. It highly depends on - elevation of the ground station - height above ground of the aircraft - terrain IIRC there is a rough approximation for the range of a VOR: range in NM equals 1.2 times sqrt( altitude in feet) That leads to 50 NM at 2000ft 75 NM at 4000ft 120 NM at FL100 170 NM at FL 200 I live some 10 NM from EDDH with nearly undisturbed line of sight and the tower is barely receivable with an icom handheld. So I think starting with a range of 10 NM on ground is reasonable. Greetings, Torsten - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
Anders Gidenstam wrote: On Tue, 13 Feb 2007, Holger Wirtz wrote: What is the normal range for the Voice-COM-Equipment in a plane? I'm no expert in this area but isn't most aviation radio communication in the VHF frequency range? I think VHF transmissions are mostly limited to line of sight unless something unusual is going on.. There's _always_ something usual going on - it's called atmosphere :-) As long as you're flying at several thousand feet over flat terrain you're likely to be in sight of the station for quite some distance. But even at good weather more than 60 nm - which I consider as a good average for the given demand - is not very realistic, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
Martin Spott wrote: Anders Gidenstam wrote: On Tue, 13 Feb 2007, Holger Wirtz wrote: What is the normal range for the Voice-COM-Equipment in a plane? I'm no expert in this area but isn't most aviation radio communication in the VHF frequency range? I think VHF transmissions are mostly limited to line of sight unless something unusual is going on.. There's _always_ something usual going on - it's called atmosphere :-) As long as you're flying at several thousand feet over flat terrain you're likely to be in sight of the station for quite some distance. But even at good weather more than 60 nm - which I consider as a good average for the given demand - is not very realistic, Martin. Hi Range of radio comms, assuming Line-of-Sight path, is a function of transmitter power, aerial gain and distance. If you google path loss calculations you'll come up with several good references. If you assume 25w transmitter power (IIRC is 17dBW), 3dB transmitter aerial gain and 0dB receive (aircraft) aerial gain and plug those into the formula then you'll get a reasonable figure... this ignores such atmospheric phenomonen as rain attenuation, ducting etc. Cheers Dene NZWN - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
Just a resend of a failed posting from earlier: I (Steve Hosgood) wrote: Anders Gidenstam wrote: On Tue, 13 Feb 2007, Holger Wirtz wrote: I know that exact range answers are depending from more parameters than only the output power... What I need is a simple number which should describe the maximum range og a COM1. For example 5 km? oder 20 km??? Hi, I think VHF transmissions are mostly limited to line of sight unless something unusual is going on.. You're right, Anders though the tricky bit is modeling the interactions between radios fitted in different classes of 'plane. Which is what I believe Holger is trying to do here. I'm not an expert either - expect at least three more people to pounce on my maths below :-) Here goes anyway It might be easiest to use an analog of real world parameters to get this sort of thing working right. Transmitters are typically rated in watts, receiver sensitivity is typically given in uV. The power received by a receiver is proportional to the power of the transmitter and inversely proportional to the square of the distance. The *voltage* received (which is what you want to know) is proportional to the square-root of that, i.e proportional to the square root of the transmitter power and inversely proportional to the distance itself. I think. So, Holger, if you arrange that all radio transmission packets in FG/MP carry the transmitter's wattage and the location of the source, you can work out the straight-line distance from yourself (call it 'd'), and then do something like: pkt = get_packet(); d = sqrt(sqr(my_x - pkt-x) + sqr(my_y - pkt-y) + sqr(my_alt - pkt-alt)); if (sqrt(pkt-transmitter_power)/d my_receiver_sensitivity) /* I can't hear this guy */ chuck_packet(pkt); else decode_packet(pkt); This sort of thing would maybe allow ATC (who might have more sensitive radios) to hear people that the local Cessna pilots can't hear. And that might be quite realistic. To improve things, you might like to make sure that the straight-line distance 'd' between yourself and the transmitter does not get close to ground. You'd have to factor in curvature of the earth and any mountains if you wanted to get it right. If the straight line gets within a couple of wavelengths of ground, you start getting attenuation and multipath distortion and all sorts of stuff(*). For a first cut, ignore all that and just use 'd'! Notice also how you could arrange to degrade packets if they get received very close to your receiver's sensitivity (you could add noise, distortion etc) which again would add to realism. My code suggestion above just models an unrealistic sharp cutoff when the signal gets too weak, but IIRC aviation radio is AM deliberately because that's *not* how AM radio behaves as it nears the sensitivity limit. Steve. (*) The BBC (amongst others) have done a load of work in this area to do with predicting service-areas of radio and TV transmitters. Some of it is on the net. - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
Hello *, ok - that was one of my typical need only one parameter question :-) I see that this is not so easy as I thaught... but it is not an insolvable problem. I think I will put a more or less complex formula insite my range detection. Thanks all! Holger -- # ## ## Holger Wirtz Phone : (+49 30) 884299-40 ## ## ## ### ## DFN-Verein Fax : (+49 30) 884299-70 ## ## ## Stresemannstr. 78E-Mail: [EMAIL PROTECTED] ## ## ## ## ### 10963 Berlin # ## ## ## GERMANY WWW : http://www.dfn.de GPG-Fingerprint: ABFA 1F51 DD8D 503C 85DC 0C51 E961 79E2 6685 9BCF - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
On 02/13/2007 09:31 AM, Holger Wirtz wrote: What I need is a simple number which should describe the maximum range og a COM1. For example 5 km? oder 20 km??? As others have pointed out, the simple answer is line of sight. See algorithms below. COM1 in a Cessna is not as one of an Airbus. Both are limited by the line-of-sight rule, and by interference. Getting a better radio for your Cessna will not help at all. Contrary to what others have said, attenuation due to air / cloud / rain / snow is negligible at VHF frequencies. http://www.tapr.org/ve3jf.dcc97.html Except as noted below, a range of 500 km should be no problem for a modest aircraft radio (e.g. KX-165) ... in a line-of-sight situation. http://www.seaerospace.com/king/kx165.htm http://www.isghq.com/calc/path_lossmain.php 1) The most relevant /fundamental/ limitation to usability is frequency congestion. It does not matter if the receiver sensitivity is 2 microvolts or half that or a hundredth of that, if there is 10 microvolts of hash on the frequency. The re-usability of UNICOM frequencies /depends/ on the line-of-sight requirement, to avoid congestive interference from innumerable other users who are out of sight. High-altitude ATC sector frequencies are reusable, but the multiplicity factor is much, much less. A stuck mike can be considered an extreme form of congestion if you like. 2) The most relevant non-fundamental issue is local interference, e.g. from bad brushes in the aircraft alternator. Improving the specifications of the radio (better Tx power and/or better Rx sensitivity) will not help at all; the only thing that will help is to get rid of the interference. In an interference situation, ATC will be able to hear you, even if you are unable to hear them ... which is why pilots are trained to transmit in the blind periodic reports of their position and intentions. === Here's a quick and dirty way to tell if two aircraft are in range of each other: For each aircraft, calculate the distance to the horizon, based on the aircraft's height above the terrain. This gives you a coverage circle. If the two circles overlap, you are in range. That is, if the sum of the radii exceeds the distance between the planes, you're in range. At the next level of fanciness, ask for the Cartesian coordinates of each airplane, interpolate 10 evenly-spaced points on the line between them, and check to see that each point is above the terrain. Ynlike the QD algorithm, this can -- roughly -- deal with the case where there is an isolated mountain or something between the two locations. - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] [OT]: Range of radios
On Tue, Feb 13, 2007 at 05:49:48PM +, Steve Hosgood wrote: [...] So, Holger, if you arrange that all radio transmission packets in FG/MP carry the transmitter's wattage and the location of the source, you can work out the straight-line distance from yourself (call it 'd'), and then do something like: pkt = get_packet(); d = sqrt(sqr(my_x - pkt-x) + sqr(my_y - pkt-y) + sqr(my_alt - pkt-alt)); if (sqrt(pkt-transmitter_power)/d my_receiver_sensitivity) /* I can't hear this guy */ chuck_packet(pkt); else decode_packet(pkt); This sort of thing would maybe allow ATC (who might have more sensitive radios) to hear people that the local Cessna pilots can't hear. And that might be quite realistic. The problem with a more sensitive radio is that real radio communication is unidirectional and my implementaion using VoIP is bidirectional based on conference rooms (a star topology). The range decision is made on the position of the plane towards the position of the tower. If this range is outside a specified range calculation (see your formula :-) and perhaps a threshold detection) the plane-client hangs up the line. For the ATC this means that he can hear _every_ voice traffic on his frequency (he has an infinite sensitive radio). Because frequencies are often more than one time occupied (world wide) the virtual frequency is a combination of ICAO and frequency. To improve things, you might like to make sure that the straight-line distance 'd' between yourself and the transmitter does not get close to ground. You'd have to factor in curvature of the earth and any mountains if you wanted to get it right. If the straight line gets within a couple of wavelengths of ground, you start getting attenuation and multipath distortion and all sorts of stuff(*). For a first cut, ignore all that and just use 'd'! Notice also how you could arrange to degrade packets if they get received very close to your receiver's sensitivity (you could add noise, distortion etc) which again would add to realism. My code suggestion above just models an unrealistic sharp cutoff when the signal gets too weak, but IIRC aviation radio is AM deliberately because that's *not* how AM radio behaves as it nears the sensitivity limit. Ok, I see... your formula and a threshold detection for eliminating flapping should be a good practice. Thanks! Holger Steve. (*) The BBC (amongst others) have done a load of work in this area to do with predicting service-areas of radio and TV transmitters. Some of it is on the net. - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier. Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnkkid=120709bid=263057dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel -- # ## ## Holger Wirtz Phone : (+49 30) 884299-40 ## ## ## ### ## DFN-Verein Fax : (+49 30) 884299-70 ## ## ## Stresemannstr. 78E-Mail: [EMAIL PROTECTED] ## ## ## ## ### 10963 Berlin # ## ## ## GERMANY WWW : http://www.dfn.de GPG-Fingerprint: ABFA 1F51 DD8D 503C 85DC 0C51 E961 79E2 6685 9BCF - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.phpp=sourceforgeCID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
