Hi Guys, I posted this on the "Piper" Forum in response to questions about ADS-B.  You guys who "Fly in the Shade" can also benefit!  Here's a further explanation of the 2020 ADS-B Upgrade requirement.  ADS-B stands for Automatic Dependent Surveillance Broadcast.  It is essentially a part of the FAA's NEXTGEN upgrade of the ATC system and an important element of the "Highway in the Sky" concept.  The 2020 requirement is to require virtually all aircraft that operate in the ATC system to have ADS-B "Out" capability.  The $7,000 box mentioned in the previous post or UAT would have ADS-B "In and Out" capability.  The real benefit to pilots is in the ADS-B "In" capability.  I'll explain in a minute.  To acheive ADS-B "Out", you need either an ADS-B capable "out" transponder or a UAT Out box.  Only a few of the current GA transponders on the market have ADS-B capability.  Most of the existing units in GA aircraft today will be obsolete.  They acheive this with a feature called "extended Squitter".  In short, in addition to the normal Mode A and C capability of the transponder, the unit, when connected to a WAAS corrected GPS, will also transmit an extensive information stream to ATC or other aircraft equipped with ADS-B "IN".  This information stream (provided primarily by the GPS) includes aircraft ID, position, Speed, destination, climbing or decending, etc.  This will obviously benefit ATC greatly by providing a more reliable source of this information (than radar) and additional info that they have not had prior.  ADS-B "IN" is were the real benefit to pilots will come and where the concept of "Highway in the Sky" can be achieved.  ADS-B "In" will provide TIS traffic information, direct traffic information (UAT to UAT) and FIS (Flight Information Service) which is the Nexrad WX you are paying for now for "free"!  WSI has already been contracted to provide that service and it is available now in certain parts of the country.  As far as I know, there is no date established for ADS-B In capability and since it's primary benefit is to the pilot, there may never be a requirement.  The goal is to ultimately make the IFR pilot, especially outside of terminal areas as "independent" as possible.  If you've ever seen a pictorial of the Highway in the Sky image on a Primary Flight Display (EFIS like the Aspen, G500/600, Chelton and the myriad of other models exploding on the market, recall the Horizon/attitude image and a box in the middle of the display.  Your job is to keep the aircraft in the middle of that box as you fly IFR.  It seems the issue of altitude and heading become less a factor than just staying in the box.  Imagine your in IFR conditions and your ADS-B UAT is monitoring another aircraft in your vacinity and suddenly detemines that the aircraft is in "conflict".  Instead of ATC calling you and warning you (although they still might), the "system" simply" moves your box so as to move you away from the conflict. totally independent from ATC.  The concept is amazing. A six year old kid with basic video game experience could easily handle "enroute IFR"!  (sorry, no 3D goggles required!)  So guys, your existing Mode A/C transponder is safe for sometime.  On the other hand, if you find the need to replace your transponder and you see yourself still owning the aircraft in 2020, you might want to consider a transponder with "Extended Squitter".  Like IFR GPS, the "serious" IFR guys jumped in 10 years ago, the rest of GA really only in the last 3-4 years.  The same will be true of ADS-B.  Those who spend a lot of time in the ATC system will jump in early and can justify the cost for the benefits.  The average GA guy will be asking for one for Christmas 2019!  Bob Hart APG-Eastern Avionics