Jason Wagner ...

^ Going to have one to two antennas up on a mast feeding
^ several (or more) scanners down below. Looking for an
^ effective way to split + amplify the signals so each
^ scanner thinks its got its own antenna.

Before you buy anything additional try all the receivers on the one or two
split signals. T-adapters and short lengths of coax from the antennas to the
receivers would be all you need. With the antennas up high and unless you're
trying to receive weak signals, the split signal might still be strong enough
for what you want to receive.

If the signals are not strong enough in that configuration then keep this in
mind when you're looking for something to buy: these are receive-only radios
that do not need to be inductively matched to a transmitter and they do not
need expensive antennas designed for high power output. A duplexer is not
required.

Frank