I can post specifics later, but I believe RG6/U is satalite cable and won't quite help ya with this.
RG58/U and RG8/U are both good coax cables and can be picked up from RadioShack.
Although RG-8 is good, RG-6 will actually work fine for a scanner application. I've used it in the past for non-critical applications and it works just fine. Much better than RG-58, in fact. RG-58 is borderline acceptable at VHF, but not for a very long run. I'd keep in under 30 feet or so if I absolutely had to use it.
To be critical, the impedence of RG-6 is 75 ohms, whereas a radio receiver is 50 ohms. The impedence mismatch is negligible in effect compared to the low loss of the RG-6, and the ease of use and availability versus RG-8.
If you're planning on doing any transmitting, use 50 ohm cable. If you're only planning on receiving, use the RG-6.
Consider these losses (@100MHz/100ft):
Remember that every 3dB represents 50% of the signal. When you boil it all down for a home scanning setup, most people can get access to RG-6 quickly (RS) and can put F connectors on without a problem.
Fewer connectors and adapters (ideally just one at each end!) and good double shielded RG-6 in between and you'll be very happy. All this applies to VHF. When 800MHz becomes the primary band of interest all this is out the window.