On Tue, 19 Jun 2007 05:16:45 -0700, eganders wrote:

Is there a low cost (possibly passive) way to port 900 MHz radio
transmissions into these buildings?


Yes. You can use something like a passive reradiator of the type used
with cell phones. You've probably seen the rear windshield antennas
which are capacitively connected to an antenna on the inside of the car.
In your case, you'd probably want a feed thru reradiator of some type.

You should be able to find what you need by using a search engine to
look for passive (re)radiator devices. You might even be able to
purchase standard cell phone reradiators for 800 MHz and trim their size
so that they have the correct dimensions for 900 MHz.