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Guest Mathias

VHF Homing Indicator possible in FS?

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My personal FS project of lifetime, the Dornier 128-6 "D-IBUF" has such an instrument on board. Two antennae side by side on the cockpit roof determine the relative direction of a VHF transmitting station that the COMM2 Radio is tuned to and within reception range. An indicator needle in the panel then points in the direction that the signal comes from. If you follow that needle you will eventually fly right over that radio transmitter.I have never seen the likes in FS-dom. Is it possible to figure out the heading and distance at which a radio station one has tuned into with the COMM2 radio is located relative to the aircraft? Rememeber, we are not talking about a VOR here, but (in real life) differential radio wave analysis.In FS the only way I can see is to somehow access the radio station database, somehow extrude the coordinates from there and the rest would be trigonometry and checking if the station is within range.Any clues anybody how this could be done?

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Greetings Mathias,You are simply describing a gauge which automatically points a needle at a non directional transmission. In other words Automatic Direction Finding.Conventional ADF works in the Medium Frequency band (MFDF) and the source is normally a Non Directional Beacon (NDB) broadcasting continuously for that purpose. The needle indicates the magnetic track to the transmitter. You are simply seeking a VDF gauge. Consequently you just need default ADF gauge code and the location of the COM source in the format required by any default ADF gauge. You should not need to write any of the code needed to calculate the magnetic track to the station. Default ADF code will do that for you. You may wish to alias a prototypical non default bitmap. The location of 'in game' VHF transmitters must be available from the scenery database since COM gauges calculate whether a transmitter using the selected VHF frequency is in reception range. One of the resident gauge authors should be able to post some code that will search the scenery database for location of the 'live' COM station rather than the location of the 'live' ADF station(s). The aerial system and associated gauge you describe is most closely associated with search and rescue (SAR) location of broadcasting emergency locator transmitters (ELTs), electronic intelligence gathering (ELINT), and some world war two night fighter, home on enemy signal receivers, but VDF has much wider application than that particular Dornier mounted system.The system you describe does normally use COM 2, but VDF is still, and was historically very much used as an approach aid via COM 1. Consequently the most interesting use of such a gauge would be to allow simulation of RAF + NATO QGH, civilian VDF, and European civilian + Luftwaffe ZZ approaches which all provide intermittent track guidance via COM 1. Ideally therefore the gauge would be able to toggle between COM 1 and COM 2. The real breakthrough in this area though would be a gauge using Doug Dawson's sound gauge to 'announce' the current magnetic track to the transmitter. Ideally there would be two versions of the gauge. Most aircraft require the version with no visible bitmaps at all, just voice track guidance. SAR aircraft and a few others would have legitimate use for the visible VDF/UDF gauge without voice. Voice only VDF in that form would also allow simulation of a virtual navigator, in any aircraft, voicing track guidance for navigation from airfield to airfield all across the world; provided the airfield had at least COM 1 in the scenery database. Airfields include aircraft carriers. Since I believe an airfield does not have to have a visible component the concept could include a

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Mathias,WOW !!!! Just a little pondering on this gave me a headache. But I think it CAN be done using standard XML and the advanced GPS variables.Let me do some experiments and get back to you? I started writing how it could be done but there where to many ifs involved..Regards,Roman[a href=http://www.wheelchairaviators.org]http://online.vatsimindicators.net/820885/1793.png[/a]

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Get it here:http://forums.avsim.net/user_files/110907.ziphttp://forums.avsim.net/user_files/110906.jpgEDIT !!!!! The Rt Click to reload is for the reloading of the panel system to make changes to the gauge.. NOT TO RELOAD THE GAUGE, IT DOES THIS AUTOMATICALLY.Regards,Roman[a href=http://www.wheelchairaviators.org]http://online.vatsimindicators.net/820885/1793.png[/a]

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Holy Moly! Excellent piece of work. I had no idea that was even possible, let alone actually *doable*. Thanks for this valuable information.Btw, apparently some of our navigational aids over here (Norway) also has embedded ATIS or weather information in audio. I'm not sure how this works though, since it seems pretty far fetched I haven't bothered investigating it. But this gauge tells me that there might exist some hidden possibilities if done correctly.Do you think it would be possible, with help from a scenery designer, to create an ATIS station on navaid frequencies that became audiable if audio were selected on the audio panel? (If that is how it works).Any ideas?

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Greetings Roman,Thank you for working on this. I confirm that your gauge works as documented. Excellent progress. At this point your gauge already represents the wireless operator, or navigator, passing the next waypoint track and range data to pilot flying, on a written 'pink slip' which pilot flying can keep in view, or tuck away and retrieve. Nice work.It is quick enough on my computer. Controllers don't always respond immediately with bearing data anyway.Is there a simple way you could suppress data display until there is a resolved solution? It would be realistic to add a randomising factor for bearing that is simply a percentage of true range. True Range / 20 might work reasonably well for maximum bearing error. Range data could obviously be withheld if required for realism.The 'invisible VDF voice gauge' I expressed an interest in just requires parsing of the required track data from your new gauge, into three separate numbers to be conditionally tested and voiced. Do you happen to have some existing xml code that parses a three digit number into three discrete variables for passing to a sound gauge? Having thought about it a little more canned ATC voice responses can be suppressed via default selectable options anyway so a gauge voice activation delay is not necessary.Would it be a lot of work to determine whether ATC at the airfield in question have assigned a landing runway to the aircraft in question and then add the assigned landing runway to the data currently available in your gauge?Can you determine the landing runway at the relevant airfield, before ATC are prompted to assign it to the aircraft in question? The landing runway must be known before any such gauge can be developed further to provide the several real types of talk down approach (QGH / SRA / GCA). Landing runway data is not strictly needed for VDF or ZZ approaches since they are pilot interpreted.>Mathias, Since ATIS is a continuous looping broadcast both in real life, and in MSFS, we can obtain 'continuous' VDF from any ATIS. If you stick to using only ATIS locations very close to the relevant destination, and there is a published non precision approach for that airfield, or a specific runway, you could use the published altitudes and tracks associated with that approach and they would be reasonably safe when making a VDF letdown using any VDF gauge with pointing needle that you create. In real life an ATIS may be switched off when the airfield it serves closes for the night. It would be switched off at other times much more readily than a navaid. That won't happen in MSFS so any ATIS will deliver what you wished for once you incorporate the COM2 location found with Roman's new gauge code into an ADF or RMI for visual track guidance.It is intermittent VDF from the approach controller on the approach frequency that interests me most since I suppose that in MSFS, (though not in real life), that will always be co-located with the (destination) airfield.>Karl, nice to talk to you again. Yes, ATIS is often on a NAV frequency in real life. Instead of receiving a Morse ident on the carrier wave from a VOR you just receive a long modulated looping voice broadcast and spoken navaid ident instead. However in MSFS ATIS is always on a discrete frequency and not paired with a navaid. Inside MSFS the 'navaid' BGLs probably have no way to access the 'voice wavs' let alone the 'correct' set of string$ in sequence. Not my area of expertise though.Your request is doable however. If you have a clear idea which MSFS ATIS

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Thanks everybody for the replies so far! It will take me some time to work out what it all means but meanwhile thanks again!!!

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Karl, FS_Aviator, Mathias,Thanks guys for the kind words. I really like fooling with the GPS vars now. The gauge I uploaded was basically to show it can be done and I have intentions to finish and upload a set if I can find some pictures of an actual VDF set/indicator. Looked all over the net but just cant find any.BTW I updated the code a bit and now it finds database items approximetly 5 times faster. Until I find some pictures of a VDF set this will be on the back burner because Karl, yes you :) have given me a new project and i believe it can work. But some experimenting with string comparitors, some how getting the Lat/Lon for the VOR and other things will need to be sorted out.The only drawback, the tuning of the VOR will then look for the closest airport with a ATIS/AWOS transmitter and use that since all comms in FS9 are located at an airport. Regards,Roman[a href=http://www.wheelchairaviators.org]http://online.vatsimindicators.net/820885/1793.png[/a]

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>Karl, nice to talk to you again. Yes, ATIS is often on a NAV>frequency in real life. Instead of receiving a Morse ident on>the carrier wave from a VOR you just receive a long modulated>looping voice broadcast and spoken navaid ident instead. A tiny nitpick... I don't think I've ever heard of an ATIS broadcast over a Nav frequancy. AWOS, however, is often broadcast over a NAV frequency, as is Flightwatch.Dan

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Greetings all,Dan, thank you for your correction. Roman, consequently pairing an ATIS broadacast to a NAV frequency may not be worth pursuing. Closest geographically would not have worked for most anyway, hence the need for careful pairing, <>If the goal is a visual indicator system, rather than the more typical audio command guidance, suitable gauges already exist, but currently use data only from the NAV database. The thing that is new is the ability to plug in data from the FS9 COM database.I have never seen a post war VDF gauge that used a needle pointer. If you intend to replicate the appearance of the system in D-IBUF you will need Mathias to send you a photo or a sketch. In the mean time you can just feed your retrieved COM data into the Microsoft default gauge in the Lockheed Vega panel since it will yield appropriate low fidelity, restricted bearing, fly left / right / on course, twin aerial, VDF indications.I am aware of two types of real post war VDF 'gauge'. The most usual is a small cathode ray tube which displays a trace along the track to the emitter, whilst it is transmitting. The British version has the designation A.D.210 and you may be able to find photos if you search with that text. It is most associated with ground station use to VDF aircraft. It is about the same size as, and looks like, any circular weather radar in a propliner, but if an aircraft already had a radar scope the trace would usually be pulled on that existing scope. Pulling a trace on a scope may be more of a challenge than you are looking for and I believe that such systems require a more complicated aerial system than was fitted to D-IBUF.Simple twin stub aerial systems look and work just like existing Lorenz Beam Approach or Standard Beam Approach course indicators. For an example of functional LBA course indicator lights see the L-049A Constellation panel by Jan Visser and Hansjoerg Naegele within the FSDZigns freeware release. In FS9 both LBA gauges and SBA gauges use modern LOC signals which are VHF, but outside the COM frequency band. With LBA, SBA or any other two light DF indicator system pilot flying turns the entire aircraft to get a light on the panel from both aerials once he or she has 'traced' the emitter and placed it between the two aerials on the airframe with equal signal strength. Pilot flying holds the signal 'on the nose' and follows a looping track to it in the crosswind. The required code, bitmaps and flying technique do not change if the emitter is in the COM band.Existing LBA gauge code as used in the L-049A is almost applicable. You just have to supply the value (current COM magnetic bearing minus 180 (corrected for negatives)) as a variable instead of reading a LOC centreline track from the NAV scenery database. Not many aircraft could use the lights for VDF in the COM band though. The vast majority used audio command track guidance.Regards,

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Roman,I PM'ed you concerning pics and documentation of the rather simple visual VHF-Homing gauge of "my" bird. Please check your Inbox and reply to the email address I gave you, will be glad to assist in any way I can to get this contraption to work and look good at the same time :-)

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Thanks so much Roman for your VHF-Homing gauge. It works like charm.And it has taught me a lot about the ACTUAL location of radio stations. Often the frequencies of some small airport in the vicinity of a real BIG airport all originate AT that BIG airport. To test the loading time in radio-dense places I chose the Indianapolis area. The only radio signal I could find OUTSIDE of KIND was the one from Columbus Municipal (KBAK). All other approach frequencies listed at different airports and -fields around Indianapolis originated from KIND. The frequencies list of KIND is extremely loooong...I will email you my slight graphics tweak of the gauge background so it fits in better with my other gauges.Thanks again!!!!!!!!!!!!!!!!!!!!!

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