Another way to approach this is to make a list of what you want to listen to. Then see how many on the list can be heard with the stock antenna that came with the scanner. If you can receive all clearly, keep your money. If you can’t get all, try monitoring outside the house, possibly on a back porch or deck with the stock antenna. (Some dwellings might have metal foil insulation battings that will make your house act like a faraday cage, reducing signal strength. But in general, all outside antennas will do better than the stock antenna while inside the house. If you hear all clearly you have just answered the question of “Do I need a more expensive antenna that touts a lot of gain?” The answer would be no. You could try a cheaper antenna or a mobile antenna. (Some outside antennas are just that, a mobile antenna but with the addition of radials. If you hear some signals that are weak, a better quality antenna may be in the mix. A discone is usually your best bet for decent coverage on all bands. It’s omnidirectional but has no gain, not that gain is important if you are lucky enough to have good signal strength at your location. If you do these things I mention here, then report back to this group, we will have a good idea of what you need in the way of an outside antenna. In any case, when installing an outside antenna onto a house, follow all the rules that apply. Stay clear of any overhead power lines and make sure an approved ground is included. (That’s usually a 4-6 foot copper rod sunk into the ground to which a wire is attached which connects to the mounting hardware of the antenna.