Here's Garmin reaching into your wallet yet again for another accessory to get full functionality from their GDL52R that you've already paid a premium for. Your GDL52R requires a TNC connection for the SXM antenna at ~$95. Go try to find a TNC SXM antenna except Garmin's  GA24TNC for about $95 and let me know how that works out for you.

If you have the GDL52 you will need a SXM antenna with an MCX connection from Garmin @ ~$99 or buy an aftermarket SXM antenna (linked below) with this adapter kit at Amazon for ~$11 HERE - then use the MCX Male to SMB Female adapter from the kit to attach your aftermarket SXM antenna. Presto ~$70 savings! 

For about $25-$35 it is possible to bypass the roughly $70 profit fattening antenna accessory from Garmin and create a functionally equivalent antenna to receive your SXM subscription.

The two items pictured below are all that's required for your GDL52R - a conventional SXM antenna at approximately $15 from eBay or $19 from Amazon HERE + a short length of SMB Male to TNC Male adapter cable at about $8, also from eBay or $18 at Amazon HERE.

Enjoy your low cost alternative to the GA24TNC or GA24MCX antenna and enjoy the 12 or so gallons of Avgas or a couple of filet mignons or that favorite adult beverage that you can spring for without feeling guilty!

PS: If you are mounting the SXM antenna near any compass or magnetometer, the usually fitted magnets in the bottom of the SXM antenna can easily be removed from behind the label on the bottom of the antenna. A hook & loop (aka Velcro) strip can then be applied to the back of the antenna for removable mounting.