Can I use a standard TV splitter to feed a signal from my discone on the
roof to two separate scanners ? Guess I will need to preamp the signal
before the splitter ?

When I had two scanners, I just bought a "T" adapter, plugged the coax from the
antenna into it, then ran short lengths of coax to each scanner and it worked
fine.
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73! de Andy KC2SSB
Beachwood, NJ USA! Grid FM29vw
http://vhfradiobuff.tripod.com