There are 4 antennas on ISS.  Each of these antennas support multi-band 
operation.  Actually 3 of the 4 antennas are identical.  Each of these 
antennas can support 2 meter, 70 cm, L band, and S band transmit and 
receive.  They also support reception of GPS and the Russian Glisser EVA TV 
system.  On the fourth antenna, the 2 meter/70 cm whip is replaced with a 
2.5 meter long whip (vertical).  This antenna will support HF operations, 
particularly 10 meters.

The Glisser system will be activated during EVAs.  Also, during EVAs, the 
ISS Ham radio system is shut down for crew safety reasons.  So we work well 
with just an A/B switch between Glisser and Ham.  This is what is being 
designed for the Phase 2 system.

Right now we could support 70 cm operation using the Ericsson radio.   We 
are still waiting for the Russians to certify the use of this equipment 
with the new antennas.  In the near future (Phase 2), we will have a 
dual-band 2 meter/70 cm radio along with the 70 cm radio.  When these two 
systems are installed, we probably will hook one up to WA1 and the other to 
WA2.  These are the two downward facing antennas.  For a while, each radio 
system will use a separate antenna system.  When we add additional 
equipment, we will evaluate the antenna uses.  For now, we don't have any L 
band or S band equipment under development, but several ideas are in the 
works.  And, of course, HF operations will use the WA4 (HF) antenna.

The International ARISS team have worked quite hard to bring these antennas 
to fruition.  The Russian provided the feedthroughs and supported the 
EVAs.  The US team did the hardware integration and certification.  The 
Italian team, U.S. team and Russian team all developed portions of the 
hardware.