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>If the packet station is left unattended for long 
>period why the crossband repeater cannot be put 
>in service and left unattended...

Its a long story, but the answer is because of PCSAT2.
PCSAT2 was supposed to have been activated on ISS
in July 2003 and be FINISHED by Jully 2004.  At that
time the Crossband repeater was not yet on board
and so to avoid any interference with 2 meter school
contacts PCSAT2 was designed with 2m uplinks and UHF

Problem is that Shuttle accident and 2 years of delays
caused PCSAT2 to actually arrive on ISS 2 years later
after the Kenwood did.  But the Kenwood was designed
(as we hope all future payloads would be designed to
avoid these kinds of problems) to have UHF uplinks 
and 2m downlinks.

So now if The Kenwood is activated with FM repeater
with 2m downlink, it will be on all-the-time and will
block any/all 2m uplinks and commanding to PCSAT2
and other payloads.  The only alternative is to 
operate the FM repeater in reverse, that is with
2m uplink and UHF downlink while PCSAT2 is still
attached (another 7 months).  But that takes 
dozens of keyboard steps to set up by the crew 
and has such a potential to get missconfigured 
especially since it would have to be done each time
after each school contact, that it appears to be just
too risky.

Hope that helps.
PCSAT2 COmmand Station
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