Kal at Appareo tech support was very gracious about revealing the connectors used on their Stratus units (I was shocked frankly as companies can be difficult about these sorts of things).
Here's the transcript:
ADS-B Connector
Connector Type (to Stratus): MS-151-C(LP) connector
Connector Type (to antenna): Reverse Polarity SMA
If you are looking to make your own ADS-B antenna cable, these links may be helpful to you:
Sporty's sells a 10 ft ADS-B cable with a reverse polarity SMA, which may prove easier than trying to find the part yourself: http://www.sportys.com/PilotShop/product/17675
Datasheet for Reverse Polarity connector to Stratus: http://www.hirose.co.jp/cataloge_hp/e35802159.pdf
If you do decide to source it yourself, here's a link to the connector that would mate with the ADS-B port: http://www.digikey.com/product-detail/en/MS-151-C(LP)/H11886-ND/241Hi5101
GPS
Connector Type: MCX Connector
GPS Antenna MCX to BNC Adapter Cable http://www.sportys.com/pilotshop/mcx-to-bnc-adapter-cable.html
Part #5955A
The external antenna is an active GPS antenna.
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I am planning to put my S2 on the hatrack where I have master switch power. If I don't get adequate reception with it back there I'll add external antennas and I am thinking of foil tape on the windows.