That's a fairly long run - I personally wouldn't use anything less than LMR 400 type coax, better still would be LMR 600 coax.
Using LMR 600, with connectors in place the signal strength your antenna receives will have dropped to around half the received strength by the time it reaches your scanner/receiver front-end - I wouldn't want to be loosing much more than that. With LMR 400 coax your signal strength losses over the 50' coax run are going to be in the region of around 30% more.
Look at this antennas' spec's online I see it has a Gain figure of just over 2dB. Nice to know, but what the spec's don't say is for what frequency that figure is for - it be for around 800Mhz - 900Mhz which is great if that is the region that interests you, or it may be at 300Mhz - 400Mhz, and at 800Mhz - 900Mhz the Gain may be negative |(-).
The point I'm making, is that your coax can have significant impact on overall signal strength - especially when you use a long coax run. Antenna performance may compensate, or it may add to losses. You need to keep this in mind.
As a rule, the thicker the coax is the less your losses will be over any given coax length.