The Symmetricom SyncServer S200/S250/S300/S350 (and others) do add 12V to the GPS antenna BNC connector. Almost everyone else uses 5V (including older Symmetricom).
You can use a DC blocker on the BNC and then add 5V to your antenna feed and use any antenna you like.
Or you can hack the unit and reconnect the bias from a 12V source to a 5V source on the main board.
I have several 5V and 12V GPS systems connected to the same antenna so I needed one that worked for all at the same time. I already had the Symmetricom 58532A antenna installed so I modified the antenna to work with 12V (5-15V +-10%). It just requires removing 2 chips (resistor and TVS) and adding 4 chips (VR, Caps, new TVS).
I use the the modified 58532A antenna and 58529A booster with 100+ feet of RG-6QS (yes, I know it's 75 ohm), grounding block, active splitter and several adapters. It works well for any GPS unit I connect (Trimble, TrueTime, Motorola, Ublox, Symmetricom, etc).