What are peoples thoughts on using these t junction 2 way SMA splitters to have 2 rtl-sdr donges to one flight aware antenna?
You're better off using 1 antenna per dongle. Splitters are literally just what their name implies: They split the power in half. So if you share an antenna between 2 dongles it will work, but each dongle will get 1/2 the signal (i.e. 3db signal reduction).
An option is to use a 0 loss splitter. I run several scanners and my ADS-B dongle off 1 discone in my attic. Electroline is a popular one and you can find them them ebay.
Many of the splitters that are designed for satellite TV reception cover a wide frequency range. For example, my splitters cover 40Mhz to 2500Mhz, with 1090Mhz being around the middle. Some also contain an amplifier. I use an in-line amplifier at the base of the antenna and the splitter amplifier just before 2 RaspPi. Such amplifiers have to be powered (usually from something between 5volts and 18volts, depending on make. This means that you have to provide a DC voltage up the antenna cable and the signal has to be decoupled from that voltage before it enters the RTL-SDR dongle. Most modern splitters do this automatically. If you are interested I can dig out some relevant links on the internet for you. However, you might need to be handy with a soldering iron if you want to create something from scratch.
