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15miles should not be a problem - with correct antenna setup. Choose/find an antenna that offers resonance for 150Mhz - 155Mhz, as opposed to a broad-bandwidth type antenna or the radio shack 800 which is going to have low Gain and loads of noise.
This will provide you with a significant reduction in noise and a Gain advantage (checkout the dB/dBi figure) for the frequency you are trying to monitor.
If its omni-directional you may/may not have to include a mast mount pre-amp and bandpass filter depending on your receivers' front-end selectivity and how much rf noise is on the air in your area, if its directional I see no prob's at all with just the antenna.
For what it worth I have a TDJ-150D from a company called Kenbotong Communications Ltd - good Gain (gives me 10.5dBi on 155Mhz) nice clean antenna factor and H/V 3dB beamwidths pretty much as good as they come, constructed as well as any European or USA product (for a Chinese made product!) - and most importantly: does what it says on the tin and does it very well. Cost - around 20bucks (plus postage).
I see no reason why that shouldn't sort things out for you.