Re: [Flightgear-devel] NAV receiver specs
Another big influence is the antenna pattern of the antenna on the aircraft. Fuselage, wing and empennage are the blocking structures of course. If you want I can have a look and get you some typical data for structure blocked signal loss. A lot of aircraft have a seperate GS antenna in the cockpit because: 1. antenna cable short (NAV unit is in cockpit usually) 2. excellent view of the runway (...) Thanks for the information. Of course, this would depend on the antenna position on the fuselage. Would it be placed underneath the aircraft? Perhaps the antenna gain might be increased in some situations by the fuselage acting as a huge reflector? Since there can be many specific situations, antenna gain will be configurable on a case by case basis. I will spend more time doing research, but would definetly appreciate if you know a reliable source for this type of information online. As I said earlier, I think it could be possible to add antenna radiation patterns, at least in a simplified way. Thinking of most GA and business aviation aircraft I know the NAV antenna (VOR/LOC/GS) is always located on the vertical tail, just below the horizontal tail with a cross or t-tail and on top of the vert. tail with a low hor. tail. These are usually two antennas, one on each side of the structure. They are on the vertical tail because NAV signals are polarized horizontally and thus the antenna must be installed that way (unlike COM which is polarized vertically and you will find these antennas standing up or down.) As I mentioned before, there is sometimes a separate GS antenna in the cockpit or on the fuselage directly above it. It looks like a small V about 30cm wide. These are all passive antennas. See http://www.cobham.com/about-cobham/aerospace-and-security/about-us/antenna-systems/fullerton/products/vorlocgs.aspx for instance Gain increase by reflection on aircraft is not something I am aware of. I know that for COM 1/4 lambda antennas (or 1/4 lambda antennas in general) you need a good ground plane to get the VSWR down to an acceptable level. Regards Eric -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] NAV receiver specs
Thinking of most GA and business aviation aircraft I know the NAV antenna (VOR/LOC/GS) is always located on the vertical tail, just below the horizontal tail with a cross or t-tail and on top of the vert. tail with a low hor. tail. These are usually two antennas, one on each side of the structure. They are on the vertical tail because NAV signals are polarized horizontally and thus the antenna must be installed that way (unlike COM which is polarized vertically and you will find these antennas standing up or down.) Thanks, I didn't know NAV is polarized horizontally (which makes sense given the need for an elevated pattern). I've been doing some reading about ground VOR equipment, and it seems there are 3 main types. Terminal VOR - around 50 W ERP, service radius approximately 25 miles under 12000 feet Low altitude VOR - power output unknown, range 80 miles under 18000 feet High altitude VOR - around 200 W, range 200 miles above 2 feet I got this information from the book Aviator's guide to GPS by Bill Clarke. Other sources on the internet which seem particularly reliable to me, mention a standard setting of 100-130 W with a maximum power of 200 W, which is set based on local site surveys. Cheers, Adrian -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] NAV receiver specs
For GA (what I have handy right now): The good old Garmin 400 series: VOR/LOC:-103.5dBm, GS:-87dBm Avidyne (EntegraII): VOR: 5uV, LOC and GS: 10uV www.repeater-builder.com/measuring-*sensitivity*/*dbm*2uv.pdf /for conversion table!/ The Avidyne is TSO minimums if I remember correctly. Their units tend to depend on GPS (and thus do not care much for radio navigation). Airline stuff goes down to like 0.5uV (so much more sensitive and expensive). They can receive a VOR signal at FL300 at quasi-optical range! Above values are all 'hard' values (like yours), so measured with a 6dB loss between the test unit and the Nav unit. If you look at specs from a European manufacturer: they usually leave out the 6dB loss! Antenna cable losses have to be added for in airplane performance (and they are usually significant). Eric On 11/25/2011 03:49 AM, Adrian Musceac wrote: Hi there, I'm about to start implementing navradio signal propagation, and I'd like to know from anyone who has experience with this type of radios whether this spec sheet performance is typical for most receivers including airline big iron, so that I should hardcode or not the values. https://www.bendixking.com/wingman/servlet/com.merx.npoint.servlets.DocumentServlet?docid=doc689082ce- f7ddb4bf1a-762df96555eb2dc6f382507bde7144eb The meaningful quoted figures for sensitivity are: VOR/LOC - 2 uV for half flag, 1 uV typical Glideslope - 12 uV typical, 20 uV for half flag Cheers, Adrian -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] NAV receiver specs
On Monday, November 28, 2011 18:31:42 Eric van den Berg wrote: For GA (what I have handy right now): The good old Garmin 400 series: VOR/LOC:-103.5dBm, GS:-87dBm Avidyne (EntegraII): VOR: 5uV, LOC and GS: 10uV www.repeater-builder.com/measuring-*sensitivity*/*dbm*2uv.pdf /for conversion table!/ The Avidyne is TSO minimums if I remember correctly. Their units tend to depend on GPS (and thus do not care much for radio navigation). Airline stuff goes down to like 0.5uV (so much more sensitive and expensive). They can receive a VOR signal at FL300 at quasi-optical range! Thanks, that is useful data! From what I could gather from different sources on the internet, typical VOR ground equipment operates with around 100-200 W ERP, am I correct? Antenna cable losses have to be added for in airplane performance (and they are usually significant). I will make the antenna gain configurable for each station/aircraft, so any cable losses can be added into the system that way. I think that losses might not be very high in the VHF airband unless the aircraft uses very crappy coax or a significant length, but that might change for GS frequencies in the 300 MHz range, of course. Cheers, Adrian -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] NAV receiver specs
On 11/28/2011 06:14 PM, Adrian Musceac wrote: On Monday, November 28, 2011 18:31:42 Eric van den Berg wrote: For GA (what I have handy right now): The good old Garmin 400 series: VOR/LOC:-103.5dBm, GS:-87dBm Avidyne (EntegraII): VOR: 5uV, LOC and GS: 10uV www.repeater-builder.com/measuring-*sensitivity*/*dbm*2uv.pdf /for conversion table!/ The Avidyne is TSO minimums if I remember correctly. Their units tend to depend on GPS (and thus do not care much for radio navigation). Airline stuff goes down to like 0.5uV (so much more sensitive and expensive). They can receive a VOR signal at FL300 at quasi-optical range! Thanks, that is useful data! From what I could gather from different sources on the internet, typical VOR ground equipment operates with around 100-200 W ERP, am I correct? That I do not know. But I do know there are long-range and short-range VOR-s with significantly different output levels. Not sure how to determine the difference easily. For NDB-s it is more easy. The short range ones are on or near the threshold and at the FAP typically. Antenna cable losses have to be added for in airplane performance (and they are usually significant). I will make the antenna gain configurable for each station/aircraft, so any cable losses can be added into the system that way. I think that losses might not be very high in the VHF airband unless the aircraft uses very crappy coax or a significant length, but that might change for GS frequencies in the 300 MHz range, of course. Well the standard in GA aircraft is RG400. Which is pretty crappy (approx. 12.5dB per 100ft). If you take a typical GA aircraft 10m in length, NAV unit in cockpit, VOR/LOC/GS antenna on the vertical tail. Antenna cable may be 15m (50ft) + one bulkhead connector (another 1.5dB?) = 7.5 dB signal loss (=38% signal strength left). Bigger aircraft have corresponding longer antenna cables and a pressure cabins (so more possible bulkhead feed-throughs: these connectors are real signal killers) which might use RG213 or even RG393. Another big influence is the antenna pattern of the antenna on the aircraft. Fuselage, wing and empennage are the blocking structures of course. If you want I can have a look and get you some typical data for structure blocked signal loss. A lot of aircraft have a seperate GS antenna in the cockpit because: 1. antenna cable short (NAV unit is in cockpit usually) 2. excellent view of the runway (...) Eric Cheers, Adrian -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] NAV receiver specs
The nav.dat file contains 'range' in nm for the nav-aid. http://data.x-plane.com/file_specs/Nav740.htm Perhaps you could use some heuristic to create a reasonable power level to meet the published range? Ron Oh I see then, my bad, I was not aware of this fact. Of course, the navradio code already does that, so I guess I'll have to forget about this issue because of data unavailability. Cheers, Adrian -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] NAV receiver specs
On Monday, November 28, 2011 20:20:03 Eric van den Berg wrote: That I do not know. But I do know there are long-range and short-range VOR-s with significantly different output levels. Not sure how to determine the difference easily. For NDB-s it is more easy. The short range ones are on or near the threshold and at the FAP typically. Ok, I understand. I will postpone any VOR-related code until I can get specific data. The whole point of this code is to increase the realism, so if real data is not available, it's better to leave it like that for now. I've looked through the navradio code written by Torsten before starting to add radio attenuation to VOR's, and it's currently calculated based on service cone radius at different altitudes. While obviously this does not take into account any terrain obstruction, it's going to be more accurate as far as range is concerned - if the attenuation code has no hard figures for power output. Well the standard in GA aircraft is RG400. Which is pretty crappy (approx. 12.5dB per 100ft). If you take a typical GA aircraft 10m in length, NAV unit in cockpit, VOR/LOC/GS antenna on the vertical tail. Antenna cable may be 15m (50ft) + one bulkhead connector (another 1.5dB?) = 7.5 dB signal loss (=38% signal strength left). Bigger aircraft have corresponding longer antenna cables and a pressure cabins (so more possible bulkhead feed-throughs: these connectors are real signal killers) which might use RG213 or even RG393. Oh, I see your point now, I was expecting at least RG58, but I now realize that weight is an issue for an aircraft. I will provide a separate field for cable+connector losses, which could be configured for each aircraft. Another big influence is the antenna pattern of the antenna on the aircraft. Fuselage, wing and empennage are the blocking structures of course. If you want I can have a look and get you some typical data for structure blocked signal loss. A lot of aircraft have a seperate GS antenna in the cockpit because: 1. antenna cable short (NAV unit is in cockpit usually) 2. excellent view of the runway (...) Thanks for the information. Of course, this would depend on the antenna position on the fuselage. Would it be placed underneath the aircraft? Perhaps the antenna gain might be increased in some situations by the fuselage acting as a huge reflector? Since there can be many specific situations, antenna gain will be configurable on a case by case basis. I will spend more time doing research, but would definetly appreciate if you know a reliable source for this type of information online. As I said earlier, I think it could be possible to add antenna radiation patterns, at least in a simplified way. Cheers, Adrian -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] NAV receiver specs
Hi there, I'm about to start implementing navradio signal propagation, and I'd like to know from anyone who has experience with this type of radios whether this spec sheet performance is typical for most receivers including airline big iron, so that I should hardcode or not the values. https://www.bendixking.com/wingman/servlet/com.merx.npoint.servlets.DocumentServlet?docid=doc689082ce- f7ddb4bf1a-762df96555eb2dc6f382507bde7144eb The meaningful quoted figures for sensitivity are: VOR/LOC - 2 uV for half flag, 1 uV typical Glideslope - 12 uV typical, 20 uV for half flag Cheers, Adrian -- All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-novd2d ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
