enhanced mode S
No one has asked the question "where dose the enhanced data for mode S come from ?"
If you all think that it will cost you a lot to go mode S then that is just the half of it !.
Enhanced mode S requires data inputs for HDG, TK , IAS , OAT , PX alt , the only way to get this is from an air data computor (ADC) these cost about $4000 this requires the HDG info from a slaved compass system that has a HDG bootstrap output and depending on the RMI system you may also need an inverter to boost the HDG syncro systen signal and then the whole thing needs linking to a top of the range GPS ( garmin GNS 430 or the like).
The down side to this is the cost , if you dont have a HSI I could see the bill hitting $15,000.
The up side is that the ADC will come with a fuel flow system and real time air data is at your finger tips , if you have the display space you will get a wind speed and direction arrow just like the airliners !.
In short the system is approaching the capabilitys of an airliner flight managment computor , and is hardly a requirement for a VFR trip across the channel.