Use SMA ports as direct output without using ALTGX

I am not sure if this is the right place to post this message, so if not please (re)move it.

I am trying to interface my FPGA design with a PCB board using the SMA ports but Quartus keeps giving me error messages, either pointing out that the selected voltage is not allowed for the SMA ports (2.5V) or that the given configuration is only possible by using ALTGX Megafunction.

I am using an Stratix IV, device EP4S100G2F40I2.

PS: I was able to use the SMA pins without problems when using the fast transceivers, with the ALTGX function. The problem now is that I need to send only bit-messages, thus not requiring all the circuitry that comes along ALTGX. The image below shows a simple scenario that illustrates pretty much what I trying to do, in which each output port is one SMA pin on the board.

Thanks in advance,

http://www.alteraforum.com/forum/attachment.php?attachmentid=11050&stc=1