From: Adrian M. <kan...@gm...> - 2011-11-29 07:13:47
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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 |