T&T: AIS antenna

[hymarks at mindspring.com]

I am planing to install an AIS receiver.  The antenna and cable included with unit has cable 15-18 feet.  This is too short for my antena cable route!  Manfacturer says extension will affect performance.  Is this mostly an SYA statement or does it really effect performance.  If so how?  What will suffer.  Will it be that I simply do not see far away boats or what.

Also I have read about antenna spliters that allow the use of one's VHF antenna to be used with thhe AIS.  That would possible be a good solution since my VHF antenna is a the top of the mast.

Also what says the group about placing antenna with respect to other antenna eg SSB , GPS or other VHF antenns.

Thanks for your comments.

Stephen Starling
 KK42