How many aerials for a repeater?

[ericmark]

I was helping prep a 30 meter mast for the repeater at work, and we had one aerial inside a white tube, which at the time did not seem wrong, but then realised only one N type connector should there not be a receive and transmit aerial?

 

[bernardgreen]

It might be there are two antennas in the tube sharing the single feeder using band pass filters ( resonant cans ? ) to direct the signals to the relevant destinations. ( TX antenna up or Receiver input down )